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The use of enzymes in medicine Enzyme preparations are widely used in medicine. Enzymes in medical practice are used as diagnostic (enzymodiagnostics) and therapeutic (enzyme therapy) agents. In addition, enzymes are used as

Introduction

1.Types of enzymes

2. Structure of enzymes

The mechanism of action of enzymes

Bibliographic list

Introduction

Enzymes are the most important class of protein substances, universal in their biological function. Enzymes are specific and highly efficient catalysts for chemical reactions occurring in a living cell. The study of enzymes, their structure, properties and mechanism of biological action is one of the main branches of biochemistry and bioorganic chemistry. To date, several thousand enzymes have been characterized, more than a thousand of them have been obtained in an individual state. For many hundreds of enzyme proteins, the amino acid sequence has been elucidated, and the most famous of them have been deciphered using X-ray diffraction analysis to the level of a complete spatial structure. The study of any problem in the field of knowledge of the mechanisms of vital activity is necessarily associated with the study of the corresponding enzyme systems. In addition, enzymes are widely used as powerful tools in elucidating the structure of biopolymers and in genetic engineering. They find wide practical application in medicine and the food industry.

Enzymatic processes have been known to man since ancient times. In particular, fermentation was widely used by the Greeks to produce wine (the discovery of this method was attributed to the god Bacchus). The peoples of many countries have long mastered the art of making bread, cheese, vinegar based on the processing of plant and animal raw materials. However, the current stage in the development of enzymology dates back to the beginning of the last century. In 1814, a member of the St. Petersburg Academy of Sciences, K. Kirchhoff, established that starch is converted into sugar under the action of certain substances found in germinating barley grains. A further step forward in this direction was made by the French chemists A. Payen and J. Pirceau, who in 1833 showed that the heat-labile factor, obtained from malt extract by precipitation with alcohol, has the ability to hydrolyze starch; they called it diastasis.

Soon a dispute broke out about the nature of fermentation, in which the largest representatives of the natural sciences of that time participated. In particular, L. Pasteur was of the opinion that fermentation is caused by living microorganisms and, therefore, is associated exclusively with their vital activity. On the other hand, Yu. Liebig and K. Bernard defended the chemical nature of fermentation, believing that it is associated with special substances like diastase (amylase). J. Berzelius in 1837 showed that enzymes are catalysts supplied by living cells. It was then that the terms "enzyme" (from Latin fermentatio - fermentation) and "enzyme" (from Greek - in yeast) appeared. The dispute was finally resolved only in 1897, when the German scientists brothers Hans and Edward Buchner showed that yeast acellular juice (obtained by rubbing yeast with diatomaceous earth) is able to ferment sugar with the formation of alcohol and CO 2. It became clear that yeast juice contains a complex mixture of enzymes (called zymase) and these enzymes are able to function. to rove both inside and outside the cells. According to one of the historians, the appearance of carbon dioxide bubbles in the Buchners' experiment meant the birth of modern biochemistry and enzymology.

Attempts to isolate enzymes in an individual state were made by many researchers, among whom A. Ya. Danilevsky, R. Wilstetter, and others should be mentioned. The protein nature of enzymes was unambiguously proven in 1926 by the American biochemist J. Sumner, who isolated the urease enzyme from seeds in crystalline form ditches. In 1930, J. Northrop received crystalline pepsin, and then trypsin and chymotrypsin. Since this period, it has become generally accepted that all enzymes are proteins.

At the end of the XIX century. on the basis of advances in the field of studying the structure of organic compounds of biological origin, it became possible to study the specificity of enzymes. At this time, E. Fischer put forward the famous position on the need for steric correspondence between the enzyme and the substrate; in his figurative expression, "the substrate fits the enzyme like a key to a lock." At the beginning of the 20th century, the foundations for studying the kinetics of enzyme action were laid.

Enzymes have different molecular weights - from 10,000 to 1,000,000 and above. They can be built from a single polypeptide chain, several polypeptide chains, or complex (sometimes polyenzymatic) complexes. The enzyme also includes non-protein components, called cofactors (cofactors), - metal ions, small organic molecules such as vitamins, etc.

Enzymes are highly efficient catalysts: they are able to increase reaction rates millions and billions of times. For example, urease (at pH 8.0, 20 0C) accelerates the hydrolysis of urea by about 1014 once.

Enzymes are highly specific catalysts. They show specificity with respect to the type of chemical reaction catalyzed, and the formation of by-products does not occur. In addition, they have a pronounced substrate specificity and, as a rule, high stereospecificity.

1. Types of enzymes

Classification of enzymes. Previously, when naming enzymes, the name of the substrate was taken as the basis with the addition of the suffix "aza"; this is how, in particular, proteinases, lipases, and carbohydrases appeared. According to the original principle, enzymes that catalyze oxidative reactions (dehydrogenases) were designated. Some enzymes have received special names - trypsin, pepsin, etc. Currently, a classification has been adopted in which enzymes are grouped into 6 classes according to the type of catalyzed reactions:

Oxidoreductases (redox reactions).

Transferases (functional group transfer reactions).

Hydrolases (hydrolysis reactions).

Lyases (reactions of cleavage of groups by non-hydrolytic means).

Isomerases (isomerization reactions).

Ligases (synthesis reactions due to ATP energy).

Within classes, enzymes are grouped into subclasses and subclasses according to the characteristics of the reactions they catalyze; on this basis, the code numbering (ciphers) of enzymes and their systematic names were compiled. The enzyme code consists of four numbers separated by dots: the first number indicates the class of the enzyme, the second and third numbers indicate the subclass and subclass, respectively, and the fourth number is the serial number of the enzyme in its subsubclass. For example, acid phosphatase has code 3.1.3.2; this means that it belongs to the class of hydrolases (3.1.3.2), the subclass of these enzymes that act on ester bonds (3.1.3.2), the subclass of enzymes that hydrolyze phosphoric acid monoesters (3.1.3.2), and the serial number of the enzyme in this subsubclass - 2 (3.1.3.2).

Enzymes that catalyze the same reaction, but isolated from different types of living organisms, differ from each other. In the nomenclature, they have a common name and one code number. Different forms of one or another enzyme are often found in the same biological species. To name a group of enzymes that catalyze the same reaction and are found in organisms of the same species, the term multiple enzyme forms is recommended. For those enzymes of the same group that have genetically determined differences in the primary structure, the term "isoenzymes" is used.

Oxidoreduct ?zy - a separate class of enzymes that catalyze the reactions underlying biological oxidation, accompanied by the transfer of electrons from one molecule (reducing agent - proton acceptor or electron donor) to another (oxidizing agent - proton donor or electron acceptor).

Reactions catalyzed by oxidoreductases generally look like this:

b? A+B ?

Where A is a reducing agent (electron donor) and B is an oxidizing agent (electron acceptor)

In biochemical transformations, redox reactions sometimes look more complicated. Here, for example, one of the reactions of glycolysis:

n + glyceraldehyde-3-phosphate + NAD +? OVER H + H ++ 1,3-diphosphoglycerate

Here, NAD acts as an oxidizing agent. +, and glyceraldehyde-3-phosphate is the reducing agent.

The systematic names of enzymes of the class are formed according to the scheme "donor: acceptor + oxidoreductase". However, other naming schemes are also widely used. When possible, the enzymes are named in the form "donor + dehydrogenase", eg glyceraldehyde-3-phosphate dehydrogenase, for the second reaction above. Sometimes the name is written as "acceptor + reductase", for example NAD +-reductase. In the particular case when the oxidizing agent is oxygen, the name may be in the form "donor + oxidase".

According to the international classification and nomenclature of enzymes, oxidoreductases belong to class 1, within which twenty-two subclasses are distinguished:

EC 1.1 includes enzymes that interact with the CH-OH group of donors;

EC 1.2 includes enzymes that interact with the aldehyde or oxo group of donors;

EC 1.3 includes enzymes that interact with the CH-CH group of donors;

EC 1.4 includes enzymes interacting with CH-NH 2a group of donors;

EC 1.5 includes enzymes that interact with the CH-NH group of donors;

EC 1.6 includes enzymes that interact with NAD H or NADP H;

EC 1.7 includes enzymes that interact with other nitrogen-containing compounds as donors;

EC 1.8 includes enzymes that interact with the sulfur-containing group of donors;

EC 1.9 includes enzymes that interact with the heme group of donors;

EC 1.10 includes enzymes that interact with diphenols and related compounds as donors;

EC 1.11 includes enzymes that interact with peroxide as an acceptor (peroxidase);

EC 1.12 includes enzymes that interact with hydrogen as a donor;

EC 1.13 includes enzymes interacting with single donors with incorporation of molecular oxygen (oxygenases);

EC 1.14 includes enzymes interacting with paired donors with incorporation of molecular oxygen;

EC 1.15 includes enzymes that interact with superoxide radicals as acceptors;

EC 1.16 includes enzymes that oxidize metal ions;

EC 1.17 includes enzymes that interact with CH or CH2 groups;

EC 1.18 includes enzymes that interact with iron-sulfur proteins as donors;

EC 1.19 includes enzymes that interact with reduced flavodoxin as a donor;

EC 1.20 includes enzymes that interact with phosphorus or arsenic as a donor;

EC 1.21 includes enzymes that interact with X-H and Y-H type molecules to form an X-Y bond;

EC 1.97 includes other oxidoreductases.

Transfer ?zy - a separate class of enzymes that catalyze the transfer of functional groups and molecular residues from one molecule to another. Widely distributed in plant and animal organisms, they are involved in the transformation of carbohydrates, lipids, nucleic and amino acids.

Reactions catalyzed by transferases generally look like this:

X+B? A+B-X.

Molecule A in here acts as a donor of a group of atoms (X), and molecule B is a group acceptor. Often, one of the coenzymes acts as a donor in such transfer reactions. Many of the reactions catalyzed by transferases are reversible.

The systematic names of class enzymes are formed according to the scheme:

"donor:acceptor + group + transferase".

Or, slightly more general names are used, when the name of either the donor or the group acceptor is included in the name of the enzyme:

"donor + group + transferase" or "acceptor + group + transferase".

For example, aspartate aminotransferase catalyzes the transfer of an amino group from an aspartic acid molecule, catechol-O-methyltransferase transfers the methyl group of S-adenosylmethionine to the benzene ring of various catecholamines, and histone acetyltransferase transfers an acetyl group from acetyl coenzyme A to histone during transcription activation.

In addition, enzymes of the 7th subgroup of transferases that transfer a phosphoric acid residue using ATP phosphate group as a donor are often also called kinases; aminotransferases (subgroup 6) are often called transaminases.

According to the international classification and nomenclature of enzymes, transferases belong to class 2, within which nine subclasses are distinguished:

EC 2.1 includes enzymes that transfer one-carbon groups;

EC 2.2 - enzymes that carry aldehyde and ketone groups;

EC 2.3 - carrying acyl residues (acyltransferases);

EC 2.4 - transferring sugar residues (glycosyltransferases);

KF 2.5 - transferring alkyl and aryl groups with the exception of the methyl residue;

KF 2.6 - carrying groups of atoms containing nitrogen;

EC 2.7 - transferring phosphorus-containing residues;

EC 2.8 - carrying groups containing sulfur;

EC 2.9 - carrying groups containing selenium.

Hydrolases are a class of enzymes that catalyze the hydrolysis of a covalent bond. The general form of the reaction catalyzed by a hydrolase is as follows:

B+H2 Oh? A-OH + B-H

The systematic name of the hydrolases includes the name of the substrate to be cleaved followed by the addition of the hydrolase. However, as a rule, in a trivial name, the word hydrolase is omitted and only the suffix "-aza" remains.

EC 3.1 ester bond esterase: nuclease, phosphodiesterase, lipase, phosphatase

CF 3.2 sugar glycosidases: amylase, hyaluronidase, lysozyme, etc.

CF 3.3 simple ether connection

EC 3.4 peptide bond protease: trypsin, chymotrypsin, elastase, thrombin, renin, etc.

EC 3.5 non-peptide carbon-nitrogen bond

CF 3.6 acid anhydride anhydride hydrolase (helicase, GTPase)

CF 3.7 carbon-carbon bond (C-C)

CF 3.8 halogen bond

EC 3.9 nitrogen-phosphorus bond (P-N)

CF 3.10 nitrogen-sulfur bond (S-N)

EC 3.11 carbon-phosphorus bond (C-P)

EC 3.12 disulfide bond (S-S)

CF 3.13 sulfur-carbon bond (C-S)

Leah ?zy (synthases) - a separate class of enzymes that catalyze the reactions of non-hydrolytic and non-oxidative rupture of various chemical bonds (C-C, C-O, C-N, C-S and others) of the substrate, reversible reactions of formation and rupture of double bonds, accompanied by the elimination or addition of groups of atoms in its place, and also the formation of cyclic structures.

In general, the names of enzymes are formed according to the scheme "substrate + lyase". However, more often the name takes into account the subclass of the enzyme. Lyases differ from other enzymes in that two substrates are involved in catalyzed reactions in one direction, and only one is involved in the reverse reaction. The name of the enzyme contains the words "decarboxylase" and "aldolase" or "lyase" (pyruvate decarboxylase, oxalate decarboxylase, oxaloacetate decarboxylase, threonine aldolase, phenylserine aldolase, isocitrate lyase, alanine lyase, ATP citrate lyase and others), and for enzymes that catalyze the reactions of water cleavage from the substrate - "dehydratase" (carbonate dehydratase, citrate dehydratase, serine dehydratase, etc.). In cases where only the reverse reaction is found, or this direction in the reactions is more significant, the name of the enzymes contains the word "synthase" (malate synthase, 2-isopropylmalate synthase, citrate synthase, hydroxymethylglutaryl-CoA synthase, etc.) .

Examples: histidine decarboxylase, fumarate hydratase.

According to the international classification and nomenclature of enzymes, lyases belong to class 4, within which seven subclasses are distinguished:

EC 4.1 includes enzymes that cleave carbon-carbon bonds, for example, decarboxylases (carboxy-lyases);

EC 4.2 - enzymes that cleave carbon-oxygen bonds, for example, dehydratase;

EC 4.3 - enzymes that cleave carbon-nitrogen bonds (amidine lyases);

EC 4.4 - enzymes that cleave carbon-sulfur bonds;

EC 4.5 - includes enzymes that cleave carbon-halogen bonds, for example, DDT-dehydrochlorinase;

EC 4.6 - enzymes that cleave phosphorus-oxygen bonds, for example, adenylate cyclase;

EC 4.99 - includes other lyases

Isomerases are enzymes that catalyze structural transformations of isomers (racemization or epimerization). Isomerases catalyze reactions like the following:? B, where B is an isomer of A.

The name of the enzyme contains the word "racemase" (alanine-racemase, methionine-racemase, hydroxyproline-racemase, lactate-racemase, etc.), "epimerase" (aldose-1-epimerase, ribulose phosphate-4-epimerase, UDP-glucuronate-4 -epimerase, etc.), "isomerase" (ribose phosphate isomerase, xylose isomerase, glucosamine phosphate isomerase, enoyl-CoA isomerase, etc.), "mutase" (phosphoglycerate mutase, methylaspartate mutase, phosphoglucomutase, etc.).

Isomerases have their own classification, EC 5 and have the following subclasses:

EC 5.1 includes enzymes that catalyze racemization (racemases) and epimerization (epimerases)

EC 5.2 includes enzymes that catalyze geometric isomerization (cis-trans isomerase)

EC 5.3 includes intramolecular oxidoreductases

EC 5.4 includes transferases (mutases)

EC 5.5 includes intramolecular lyases

EC 5.99 includes other isomerases, including topoisomerases

Ligases (synthetases). The class of ligases includes enzymes that catalyze the synthesis of organic substances from two initial molecules using the energy of the decay of ATP (or another nucleoside triphosphate). Their systematic name is in the form "X: Y ligase", where X and Y denote the starting substances. An example is L-glutamate:ammonia ligase (recommended abbreviation "glutamine synthetase"), with the participation of which glutamine is synthesized from glutamic acid and ammonia in the presence of ATP.

Ligases are classified according to the type of bond they catalyze: O-ligaseS-ligaseN-ligaseC-ligase

Structure of enzymes

In nature, there are both simple and complex enzymes. The former are entirely represented by polypeptide chains and, upon hydrolysis, decompose exclusively into amino acids. Such enzymes (simple proteins) are hydrolytic enzymes, in particular pepsin, trypsin, papain, urease, lysozyme, ribonuclease, phosphatase, etc. Most natural enzymes belong to the class of complex proteins containing, in addition to polypeptide chains, some non-protein component (cofactor ), the presence of which is absolutely essential for catalytic activity. Cofactors can have a different chemical nature and differ in the strength of the bond with the polypeptide chain. If the dissociation constant of a complex enzyme is so small that in solution all polypeptide chains are associated with their cofactors and are not separated during isolation and purification, then such an enzyme is called a holoenzyme (holoenzyme), and the cofactor is called a prosthetic group, considered as an integral part of the enzyme molecule. The polypeptide part of the enzyme is called the apoenzyme.

In the literature, other names for the components of complex enzymes are still used, in particular, “enzyme-protein”, “protein component” (apoenzyme), “coenzyme” (coenzyme) and “prosthetic group”. A coenzyme is often understood as an additional group that is easily separated from the apoenzyme during dissociation. It is assumed that the prosthetic group can be associated with the protein by covalent and non-covalent bonds. Thus, in the acetylcoenzyme-A-carboxylase molecule, the biotin cofactor is covalently bound to the apoenzyme via an amide bond. On the other hand, chemical bonds between cofactors and peptide chains can be relatively weak (eg, hydrogen bonds, electrostatic interactions, etc.). In such cases, during the isolation of enzymes, complete dissociation of both parts is observed, and the isolated protein component is devoid of enzymatic activity until the missing cofactor is added from the outside. It is to such isolated low molecular weight organic substances that the term “coenzyme” is applicable, typical representatives of which are vitamins B1, B2, B6, PP, containing coenzymes. It is also known that both prosthetic groups and coenzymes are actively involved in chemical reactions, acting as intermediate carriers of electrons, hydrogen atoms, or various functional groups (for example, amine, acetyl, carboxyl). In such cases, the coenzyme is considered as a second substrate, or cosubstrate.

The role of coenzyme (Co) as a carrier of, for example, hydrogen atoms can be represented as a scheme, where SH is a substrate, KoE is a holoenzyme, A is a proton acceptor:

The substrate undergoes oxidation, donating electrons and protons, and CoE undergoes reduction, accepting electrons and protons. In the next half-reaction, the reduced CoEN can donate electrons and protons to some other intermediate electron and proton carrier or to the final acceptor.

Coenzyme, cofactor, prosthetic group - ambiguous biochemical jargon. The terminological dispute is still ongoing, since the definitions of "coenzyme", "cofactor" and "prosthetic group" are often considered through the prism of their role in the reactions of enzymatic (enzymatic) catalysis. However, one should take into account the indisputable fact that in many cases non-protein organic molecules, like metal ions, are absolutely necessary for the protein component when performing a certain biological function that is not related to biocatalysis. Undoubtedly, the type and nature of the bond between the non-protein component and the protein molecule also matter. Therefore, it is obvious that any factor that is absolutely necessary for the protein to fulfill its catalytic or any other biological role can serve as a cofactor. On the other hand, a coenzyme can be any non-protein factor that is directly involved in the enzymatic catalysis reaction. A cofactor that is not directly involved in the act of catalysis is not a coenzyme. At the same time, a prosthetic group (a covalently bound non-protein component required for a specific function) can be called a coenzyme if it is directly involved in the enzymatic reaction. A prosthetic group that is not involved in the act of catalysis, but is functionally essential for both the enzyme and the non-catalytic protein, can be called a cofactor. Finally, a cofactor and coenzyme that are loosely (or loosely bound) to an enzyme or protein are not classified as prosthetic groups, however.

Many divalent metals (Mg 2+, Мn 2+, Ca 2+) also act as cofactors, although they are neither coenzymes nor prosthetic groups. Examples are known when metal ions are strongly associated with a protein molecule, performing the functions of a prosthetic group. In particular, the purified enzyme that catalyzes the oxidation of ascorbic acid (vitamin C) to deoxyascorbic acid contains 8 copper atoms per molecule; all of them are so tightly bound to the protein molecule that they are not even exchanged with ion-exchange resins and are not separated by dialysis. Moreover, using the method of electron paramagnetic resonance, the participation of copper ions in the intermediate electron transfer was shown. It is interesting to note that free copper ions are also endowed with catalytic activity during the oxidation of ascorbic acid, however, this activity increases many thousands of times if copper ions combine with the apoenzyme into a single complex - the holoenzyme.

Evidence has been obtained of the cofactor function in enzymatic reactions and a number of other biologically active compounds that are not related to vitamins: HS-glutathione, ATP, lipoic acid, nucleoside derivatives (uridine phosphate, cytidine phosphate, phosphoadenosine phosphosulfate), porphyrin-containing substances, etc. This may also include tRNA, which, as part of the enzymes aminoacyl-tRNA synthetases, are actively involved in the transport of amino acids in the ribosome, where protein synthesis is carried out.

One distinguishing feature of two-component enzymes should be noted: neither the cofactor separately (including most coenzymes) nor the apoenzyme itself is endowed with catalytic activity, and only their combination into a single whole, which does not proceed chaotically, but in accordance with the program of their structural organization, provides rapid the course of a chemical reaction.

Active site of enzymes.

When studying the mechanism of a chemical reaction catalyzed by enzymes, the researcher is always interested not only in determining the intermediate and final products and elucidating the individual stages of the reaction, but also in the nature of those functional groups in the enzyme molecule that ensure the specificity of the enzyme action on a given substrate (substrates) and high catalytic activity. . We are talking, therefore, about the exact knowledge of the geometry and tertiary structure of the enzyme, as well as the chemical nature of that section (s) of the enzyme molecule, which provides a high rate of the catalytic reaction. Substrate molecules involved in enzymatic reactions are often small in size compared to enzyme molecules; therefore, it was suggested that during the formation of enzyme-substrate complexes, a limited part of the amino acids of the peptide chain obviously comes into direct contact with the substrate molecule. Hence the idea of ​​the active center of the enzyme arose. An active center is a unique combination of amino acid residues in an enzyme molecule that ensures its direct binding to a substrate molecule and direct participation in the act of catalysis. It has been established that in complex enzymes, prosthetic groups are also included in the composition of the active center.

The active center conventionally distinguishes between the so-called catalytic center, which directly enters into chemical interaction with the substrate, and the binding center, or contact (“anchor”) site, which provides specific affinity for the substrate and the formation of its complex with the enzyme. In turn, the substrate molecule also contains functionally different sites: for example, substrates of esterases or proteinases - one specific bond (or group of atoms) that is attacked by the enzyme, and one or more sites that are selectively bound by the enzyme.

Experimental evidence has been obtained for the presence of two histidine residues and a serine residue in the active site of chymotrypsin, which are schematically represented in a three-dimensional structural model of the precursor of this enzyme. Revealing the chemical nature and probable topography of active site groups is a problem of paramount importance. It comes down to determining the nature of amino acids, their sequence and position in the active center. To identify the so-called essential amino acid residues, specific enzyme inhibitors are used (often these are substrate-like substances or analogs of coenzymes), methods of "soft" (limited) hydrolysis in combination with chemical modification, including selective oxidation, binding, substitution of amino acid residues, etc.

Using inhibitor analysis methods, attempts were made to establish regularities in the composition and structure of active sites in enzymes belonging to different groups. In particular, when using diisopropylfluorophosphate (DFP), which belongs to the so-called nerve poisons, there is a complete shutdown of the active center of cholinesterase, an enzyme that catalyzes the hydrolysis of acetylcholine into choline and acetic acid. It turned out that this inhibitor has a close structural similarity to acetylcholine and similarly interacts with the OH group of the serine residue in the active site. Causing phosphorylation of serine in the active center of a number of other enzymes, DPP also inactivates their action:

It was shown that DPP selectively phosphorylates only one serine residue endowed with functional activity in each enzyme sensitive to it. Considering this mechanism of action of DPP, attempts have been made to determine the nature of the amino acids in the environment of the "catalytic" serine residue in a number of enzymes.

In addition to the active center, an allosteric center (or centers) may also be present in the enzyme molecule (from the Greek allos - another, different and steros - spatial, structural), which is a section of the enzyme molecule that binds certain, usually low molecular weight, substances (effectors , or modifiers), whose molecules differ in structure from the substrates. The attachment of an effector to an allosteric center changes the tertiary and often also the quaternary structure of the enzyme molecule and, accordingly, the configuration of the active site, causing a decrease or increase in enzymatic activity. Enzymes, the activity of the catalytic center of which undergoes a change under the influence of allosteric effectors that bind to the allosteric center, are called allosteric enzymes.

A distinctive feature of a number of allosteric enzymes is the presence in the molecule of the oligomeric enzyme of several active centers and several allosteric regulatory centers that are spatially distant from each other. In an allosteric enzyme, each of the two symmetrically constructed protomers contains one active site that binds the S substrate and one allosteric site that binds the M2 effector, i.e. 2 centers in one enzyme molecule. Evidence has been obtained that for the substrate, allosteric enzymes, in addition to the active center, also contain the so-called effector centers; upon binding to the effector site, the substrate does not undergo catalytic conversion, but it affects the catalytic efficiency of the active site. Such interactions between centers that bind ligands of the same type are called homotropic interactions, and interactions between centers that bind ligands of different types are called heterotropic interactions.

Thus, in enzymatic catalysis, as in the substrate binding reaction, not a limited and small part of the enzyme, as previously assumed, but a much larger part of the protein-enzyme molecule is involved. These circumstances, most likely, can explain the large size and volume of the three-dimensional structure of the enzyme molecule; the same circumstances should be taken into account in programs for the creation of artificial low-molecular analogues of enzymes (synzymes) that have the properties of native enzymes.

The mechanism of action of enzymes

enzyme biological catalysis transamination

The discovery of the spatial structure of a number of enzymes by X-ray diffraction analysis provided a reliable basis for constructing rational schemes of their mechanism of action.

Establishing the mechanism of enzyme action is of key importance for revealing structural and functional relationships in a variety of biologically active systems.

Lysozyme is found in various tissues of animals and plants, it is found, in particular, in tear fluid and egg white. Lysozyme functions as an antibacterial agent by catalyzing the hydrolysis of the cell walls of a number of bacteria. This polysaccharide is formed by alternating N-acetylmuranoic acid (NAM) residues linked ?-1,4-glycosidic bond (polysaccharide chains are cross-linked by short peptide fragments).

The bacterial polysaccharide is a very complex insoluble compound; therefore, well hydrolysable oligosaccharides formed by NAG residues are often used as lysozyme substrates.

Chicken egg protein lysozyme is formed by a single polypeptide chain containing 129 amino acid residues; its molecular weight is 14,600. The high stability of the enzyme is ensured by the presence of four disulfide bridges.

Information about the active center and the type of catalytic process was obtained by D. Philips in 1965. based on X-ray diffraction studies of lysozyme and its complexes with inhibitors. The lysozyme molecule has the shape of an ellipsoid with axes 4.5*3*3 nm; between the two halves of the molecule is a "gap" in which the binding of oligosaccharides occurs. The walls of the gap are formed mainly by the side chains of non-polar amino acids, which ensure the binding of non-polar molecules of the substrate, and also include the side chains of polar amino acids, which are capable of forming hydrogen bonds with the acylamino and hydroxyl groups of the substrate. The size of the gap allows to accommodate an oligosaccharide molecule containing 6 monosaccharide residues. Using X-ray diffraction analysis, establish the nature of the binding of the substrate, for example, NAG hexasaccharide 6, fails. At the same time, complexes of the enzyme with the trisaccharide inhibitor NAG 3stable and well studied. NAG 3binds in a gap on the surface of the enzyme, forming hydrogen bonds and van der Waals contacts; at the same time, it fills only half of the gap, in which three more monosaccharide residues can bind. The non-reducing end (sugar A) is at the beginning of the gap, and the reducing end (sugar C) is in its central part; sugar residues A, B and C have a chair conformation. The construction of a model of the enzyme-substrate complex was based on the assumption that upon binding of the NAG substrate 6the same interactions are realized as in the binding of NAG 3. In the enzyme model, three sugar residues (referred to as residues D, E, and F) were placed inside the gap; each subsequent sugar was attached in such a way that its conformation was the same (as far as possible) as that of the first three sugars. As part of the model complex, all sugar residues implement effective non-covalent interactions with side and peptide groups of amino acid residues that form a gap.

When identifying catalytic groups, it was natural to focus on those that are in the enzyme-substrate complex near the cleavable glycosidic bond and can serve as proton donors or acceptors. It turned out that on one side of the split bond, at a distance? 0.3 nm (from the oxygen of the glycosidic bond), the carboxyl group of Glu-35 is located, and on the other (at the same distance) the carboxyl group of Asp-52, their environment is very different. Glu-35 is surrounded by hydrophobic residues; it can be assumed that at the optimum pH of the enzyme, this group is in a non-ionized state. The environment of Asp-52 is pronounced polar; its carboxyl group participates as a hydrogen acceptor in a complex network of hydrogen bonds and probably functions in an ionized state.

The following scheme of the catalytic process during the hydrolysis of the oligosaccharide has been proposed. The non-ionized carboxyl group of Glu-35 acts as a proton donor, supplying it to the glycosidic oxygen atom between the C atom (1)sugar D and atom C ( 4)sugar E (general acid catalysis step); this results in the breaking of the glycosidic bond. As a result, the sugar residue D passes into the state of a carbocation with a positively charged carbon atom C (1)and assumes a half-chair conformation. The negative charge of the Asp-52 carboxylate group stabilizes the carbocation. Remaining NAG 2(sugar E+F) diffuses from the active site region. Then a water molecule enters the reaction; its proton goes to Glu-35, and OH --group to C atom (1)residue D (basic catalysis step). Remaining NAG 4(sugar A + B + C + D) leaves the region of the active center, and the enzyme returns to its original state.

Ribonuclease (RNase) of the bovine pancreas hydrolyzes internucleotide bonds in RNA near pyrymylin units, which remain esterified at 3 -position. The enzyme, along with other nucleases, is widely used in the analysis of the structure of RNA.

RNase is formed by one polypeptide chain containing 124 amino acid residues, and its molecular weight is 13,680; There are four disulfide bonds in the molecule. RNase is the first enzyme for which a primary structure has been established.

Based on the results of the study of ribonuclease renaturation, K. Afinsen for the first time clearly formulated the idea that the spatial structure of a protein is determined by its primary structure.

In 1958, F. Richards showed that, under certain conditions, subtilisin cleaves the peptide bond Ala-20 - Ser-21 in RNase. The resulting fragments were called S-peptide (residues 1-20) and S-protein (residues 21-124); due to non-covalent interactions, the fragments form a complex called RNase S. This complex has almost the full catalytic activity of the native enzyme; in isolated form, S-peptide and S-protein are inactive. Further, it was found that a synthetic peptide identical in sequence to the S-peptide fragment containing residues 1 to 13 restores the activity of the S-protein, but a shorter peptide containing residues 1 to 11 does not have this ability. The data obtained allowed us to conclude that the corresponding His-12 or Met-13 residues (or both of these residues) are included in the active site of the enzyme.

When studying the effect of pH on RNase activity, the important role of protein functional groups with pK 5.2 and 6.8 was elucidated; this suggested the participation of histidine residues in the catalytic process.

Upon carboxylation of RNase with iodoacetate at pH 5.5, i.e. under conditions under which the modification of histidine residues predominantly occurs, a complete loss of activity was observed; the modified enzyme contains 1 mol of carboxymethyl groups per 1 mol of protein. As a result, two monocarboxymethylene forms of the enzyme are formed. In one form, His-12 is carboxymethylated, and in the other, His-119. His-119 was predominantly modified.

These data suggested that His-12 and His-119 are in the active site and that modification of one of them prevents modification of the other.

As a result of X-ray diffraction studies, the spatial structure of RNase S and the complex of RNase S with inhibitors was elucidated. The molecule has the shape of a kidney, the active center is localized in the depression where the residues of His-12, His-119 and Lys-41 are located.

Hydrolysis occurs as a result of the conjugated action of His-12 and His-119 residues, which carry out acid-base catalysis. The diagram below shows the stages of the catalytic process:

1.The substrate is in the active site; His-12, His-119 and Lys-41 are located near the negatively charged phosphate.

2.As a result of the action of His-12 as a proton-accepting base from 2 -OH groups of ribose, and His-119 as an acid that donates a proton to the oxygen atom of phosphate, an intermediate complex is formed first, and then 2 ,3-cyclic phosphate.

.In place of the departed product, water enters, donating the His-119 proton, and OH -- phosphate, at the same time the proton from His-12 passes to the oxygen atom of ribose, the second product is formed, and the enzyme returns to its original state.

Chymotrypsin is secreted in the form of a proenzyme - chymotrypsinogen by the pancreas of vertebrates; proenzyme activation occurs in the duodenum under the action of trypsin. The physiological function of chymotrypsin is the hydrolysis of proteins and polypeptides. Chymotrypsin attacks mainly peptide bonds formed by carboxyl residues of tyrosine, tryptophan, cenylalanine and methionanine. It also effectively hydrolyses the esters of the corresponding amino acids. The molecular weight of chymotrypsin is 25,000, the molecule contains 241 amino acid residues. Chymotrypsin is formed by three polypeptide chains linked by disulfide bridges.

The functional groups of the active site of chymotrypsin have been identified using irreversible inhibitors. The Ser-195 residue was modified with diisopropyl fluorophosphate and phenylmethylsulfofluoride, and the His-122 residue was modified with N-tosyl-L-phenylalanine-chloromethyl ketone. The two-stage process of chymotrypsin hydrolysis was discovered in the study of the kinetics of hydrolysis of p-nitrophenylacetate.

A characteristic feature of the process under consideration is the formation of a covalent intermediate, an acyl enzyme. The acylated catalytic group was identified as the residue Ser-195. The mechanism of catalysis carried out by the enzyme was proposed even before the establishment of the spatial structure of the protein, but was later refined. In particular, research with 18H 2O made it possible to prove the formation of an acyl enzyme during the hydrolysis of peptides.

A three-dimensional structure with a resolution of 0.2 nm was established by D. Blow's X-ray diffraction analysis. in 1976 The molecule has the shape of an ellipsoid with axes 5.4*4*4 nm. The results of crystallographic studies confirmed the assumption that the Ser-195 and His-57 residues are close. The hydroxyl group of Ser-195 is located at a distance of ~0.3 nm orth of the nitrogen atom of the His-57 imidazole ring. The most interesting circumstance was that the nitrogen atom in position 1 of the ring is at a distance of ~0.28 nm from the oxygen atom of the carboxyl group of the Asp-102 side chain and occupies a position favorable for the formation of a hydrogen bond.

It should be noted that chemical studies could not reveal the involvement of Asp-102 in the functioning of the active center, since this residue is embedded deep into the molecule.

It is currently believed that the three residues Asp-102, His-57 and Ser-195 form a charge transfer system that plays a critical role in the catalysis process. The functioning of the system ensures the effective participation of His-57 in catalysis as an acid-base catalyst and increases the reactivity of Ser-195 to the carboxyl carbon of the attacked bond.

The key element of catalysis is the proton transfer from Ser-195 to His-57. At the same time, the oxygen atom of serine attacks the carbonyl carbon atom of the substrate with the formation of first an intermediate tetrahedral compound (1), and then an acyl enzyme (2). The next step is deacylation. The water molecule enters the charge transfer system, and the OH ion -simultaneously attacks the carbonyl carbon atom of the acyl group of the acyl enzyme. As in the acylation step, an intermediate tetrahedral compound (4) is formed. His-57 then donates a proton to the oxygen atom of Ser-195, releasing the acyl product; it diffuses into the solution, and the enzyme returns to its original state.

Carboxypeptidase A is secreted as a proenzyme by the pancreas of vertebrates. The formation of the active enzyme occurs in the small intestine with the participation of chymotrypsin. The enzyme sequentially cleaves off C-terminal amino acid residues from the peptide chain, i.e. is an exopeptidase.

Carboxypeptidase A is formed by a single polypeptide chain containing 307 amino acid residues; the molecular weight is 34,470. The amino acid sequence of the protein was established in 1969 by R. Bredshaw.

Elucidation of the mechanism of action of the enzyme was possible only after X-ray diffraction studies. The spatial structure of the enzyme and its complex with the Gly-Tyr dipeptide (substrate model) was established by W. Lipscomb. The enzyme molecule has the shape of an ellipsoid with axes 5.0*4.2*3.8 nm; the active center is located in a depression that passes into a deep non-polar pocket. A zinc ion is localized in the active center zone (its ligands are the side chains of Glu-72, His196, His-69 residues and a water molecule), as well as functional groups involved in substrate binding and catalysis - Arg-145, Glu-270 and Tyr-248.

A comparative analysis of the structures of the enzyme and its complex with Gly-Tyr yielded important information on the structure of the enzyme-substrate complex. In particular, it was found that during the formation of the complex, the hydroxyl group of Tyr-248 moves 1.2 nm relative to its position in the free enzyme (i.e., approximately 1/3 of the molecule diameter).

According to the scheme of the catalytic process, the carboxylate group of Glu-270 activates a water molecule located in the reaction sphere, pulling a proton from it; the resulting OH- ion carries out a nucleophilic attack on the carbonyl carbon of the cleavable bond. At the same time, the hydroxyl group of Tyr-248, located near the nitrogen atom of the cleavable peptide bond, donates a proton to it. As a result, the attacked peptide bond is cleaved and the resulting products leave the active site zone. The diagram below illustrates the general basic catalysis.

Aspartate aminotransferase catalyzes the reversible transamination reaction.

The enzymatic transamination reaction was discovered by A.E. Braunstein and M.G. Kritzman in 1937 in the study of an enzyme preparation from the muscle of a pigeon. In subsequent studies, it was shown that transamination reactions are widespread in wildlife and play an important role in the conjugation of nitrogen and energy metabolism.

In 1945, it was found that pyridoxal-5 -phosphate (PLF) is a coenzyme of aminotransferases. The AAT molecule is a dimer formed by identical subunits. In the cardiac muscle of the studied vertebrates, there are two isoenzymes - cytoplasmic (cAAT0) and mitochondrial (mAAT) aminotransferases.

The primary structure of cAAT from cardiac muscle was established in 1972. Yu.A. Ovchinnikov and A.E. Brainstein. The polypeptide chain of a protein contains 412 amino acid residues; molecular weight is 46,000.

The general theory of pyridoxal catalysis was developed by A.E. Braunstein and M.M. Shemyakin in 1952-1953, and somewhat later - D.E. Metzler and E.E. Snell. According to this theory, the catalytic action of pyridoxal enzymes is due to the ability of the aldehyde group of pyridoxal phosphate to form aldimines (Schiff bases) when interacting with amines, including amino acids.

In the resulting phosphopyridoxyldeneamino acid, there is a system of conjugated double bonds, along which there is a shift of electrons from ?-carbon atom makes it easier to break the bonds formed by this atom.

Modern ideas about the mechanism of enzymatic transamination, developed by A.E. Braunstein and his collaborators are a development of the above theory. In the initial state, the aldehyde group of pyridoxal phosphate forms an aldimine bond with ?-the amino group of the Lys-258 residue of the active site (I). Upon binding of the amino acid, a Michaelis complex (II) is formed, followed by an aldimine between pyridoxal phosphate and substrate (III). As a result of subsequent transformations through intermediate stages (IV) and (V), oxo acid (VI) is formed. This completes the first half-reaction of transamination. Repeating these same steps in the "reverse" direction with the new hydroxy acid constitutes the second half-reaction that completes the catalytic transamination cycle.

Myoglobin and hemoglobin

These two proteins are often referred to as respiratory enzymes. Their interaction with the substrate, oxygen, has been elucidated in detail, primarily on the basis of high-resolution X-ray diffraction analysis. The three-dimensional structure of myoglobin was determined by J. Kendrew in 1961, and the three-dimensional structure of hemoglobin - by M. Perutz in 1960.

The myoglobin molecule has a compact shape - 4.5 * 3.5 * 2.5 nm, the polypeptide chain forms 8 helical sections, denoted by letters from A to H. It is arranged in a specialized way around a large flat iron-containing heme ring. Heme is a complex of porphyrin with ferrous iron.

The polar heme propionic acid chains are located on the surface of the molecule, the rest of the heme is embedded in the globule. The connection of heme with the protein is carried out due to the coordination bond between the iron atom and the histidine atom, localized in the F helix; this is the so-called proximal histidine. Another important histidine residue, distal histidine, is localized in the heme pocket in the E helix; it is located on the opposite side of the iron atom at a greater distance than the proximal histidine. The region between the gene iron and the distal histidine in deoxymyoglobin is free, and the lipophilic O molecule 2can bind to heme iron, occupying the sixth coordination position. A unique feature of myoglobin, as well as hemoglobin, is their ability to reversibly bind O 2without heme Fe oxidation 2+in Fe 3+. This is possible because a low permittivity medium is created in the hydrophobic heme pocket from which water is displaced.

When linking O 2with the iron atom, the latter moves by about 0.06 nm and ends up in the plane of the porphyrin ring, i.e. in an energetically more favorable position. It is assumed that this movement is due to the fact that the Fe ion 2+in deoxymyoglobin is in a high-spin state and its radius is too large to fit in the plane of the heme porphyrin ring. When linking O 2Fe ion 2+ goes into a low-pin state and its radius decreases; now Fe ion 2+can move into the plane of the porphyrin ring.

Hemoglobin is the main component of red blood cells that delivers oxygen from the lungs to the tissues, and carbon dioxide from the tissues to the lungs. Hemoglobins of different types differ in the form of crystals, solubility, affinity for oxygen. This is due to differences in the amino acid sequence of proteins; the heme component is the same in hemoglobins of all vertebrate species and some invertebrates.

Human hemoglobin is a tetramer composed of four subunits, two ?-subunits and two ?-subunits containing 141 and 146 amino acid residues, respectively. between primary structures ?- and ?-subunits there is significant homology, and the conformation of their polypeptide chains is also similar.

The hemoglobin molecule has a spherical shape with a diameter of 5.5 nm. The four subunits are packed in a tetrahedral shape.

X-ray diffraction data showed that oxygenation of hemoglobin is accompanied by a number of changes. At low resolution, it was found that in this case the structure becomes more compact (Fe atoms ?-chains approach each other by about 0.6-0.7 nm), the subunits rotate relative to each other and the second-order axis by 10-15 about . The results of the study at high resolution indicate that especially significant changes occur in the region of ?? contacts.

To date, based on X-ray diffraction studies and a number of other methodological approaches, significant progress has been made in elucidating the mechanism of action of enzymes with desired properties based on achievements in the field of genetic engineering. This opens up wide opportunities for testing the validity of modern ideas about the mechanism of enzyme action and creating a fundamental theory of enzymatic catal.

Bibliographic list

1. A. Lehninger Fundamentals of biochemistry. - Moscow World, 1985.

Yu.A. Ovchinnikov. Bioorganic chemistry. - Moscow Enlightenment, 1987.

T.T. Berezov, B.F. Korovkin. Biological chemistry. - Moscow Medicine, 1990.

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The human body is made up of a huge number of living cells. A cell is considered a unit of a living organism, it consists of structural bodies, between which biochemical reactions take place. An important component that controls the conduct of chemical processes are enzymes.

The role of enzymes in the body

An enzyme is a protein that speeds up the flow of chemical reactions, mainly it serves as an activator of the breakdown and formation of new substances in the body.

Enzymes serve as catalysts for biochemical reactions. They greatly speed up the process of life. They control the processes of splitting, synthesis, metabolism, respiration, blood circulation, without them, reactions to muscle contraction and nerve impulses do not pass. Each structural element contains its own unique set of enzymes, and when the content of one enzyme is excluded or reduced, significant changes occur in the body, leading to the appearance of pathologies.

Enzyme classification

Depending on the structure, there are two groups of enzymes.

• Simple enzymes are of a protein nature. They are produced by the body.
• Complex enzymes consisting of a protein component and a non-protein base. Non-protein components are not synthesized in the human body and come to us along with nutrients, they are called coenzymes. Non-protein substances that are part of enzymes include B vitamins, vitamin C, and some trace elements.

Enzymes are classified according to the functions they perform and the type of reactions they catalyze.

According to their functions, enzymes are divided into:

1. Digestive, responsible for the breakdown of nutrients, are found mainly in saliva, mucous membranes, pancreas and stomach. Known enzymes are:
   • amylase, it breaks down complex sugars (starch) into simple ones, sucrose and maltose, which can then participate in the vital processes of the body;
   • lipase is involved in the hydrolysis of fatty acids, breaks down fats into components that are absorbed by the body;
   • proteases regulate the breakdown of proteins into amino acids.
2. Metabolic enzymes control metabolic processes at the cellular level, participate in redox reactions, protein synthesis. These include: adenylate cyclase (regulate energy metabolism), protein kinases and protein dephosphatase (involved in the process of phosphorylation and dephosphorylation).
3. Protective ones are involved in the reactions of the body's opposition to harmful bacteria and viruses. An important enzyme is lysozyme, it breaks down the shells of harmful bacteria and activates a number of immune reactions that protect the body from inflammatory reactions.

Enzymes are divided into 6 classes according to the type of reactions:

1. Oxidoreductases. Numerous group of enzymes that are involved in redox reactions.
2. Transferases. These enzymes are responsible for the transfer of atomic groups, and are involved in the breakdown and synthesis of proteins.
3. Hydrolases cleave bonds and promote water molecules to be incorporated into the composition of body substances.
4. Isomerases catalyze reactions in which one substance enters into the reaction and one substance is formed, which subsequently participates in the life process. Thus, isomerases serve as converters of various substances.
5. Lyases are involved in reactions in which metabolic substances and water are formed.
6. Ligases provide the formation of complex substances from simpler ones. Participate in the synthesis of amino acids, carbohydrates, proteins.

Why does enzyme deficiency occur and why is it dangerous?

With a lack of enzymes, failures begin in the general system of the body, which lead to serious diseases. To maintain the optimal balance of enzymes in the body, it is necessary to balance your diet, since these substances are synthesized from the elements that we eat. Therefore, it is very important to ensure the intake of microelements, vitamins, useful carbohydrates, proteins. They are mainly found in fresh fruits, vegetables, lean meats, organ meats, and fish, whether steamed or baked.

Poor diet, drinking alcohol, fast food, energy and synthetic drinks, as well as foods containing a large amount of dyes and flavor enhancers, adversely affect the work of the pancreas. It is she who synthesizes the enzymes responsible for the breakdown and transformation of nutrients. Malfunctions of the enzymatic activity of the pancreas lead to obesity, acute diseases of the stomach and intestines, subsequently, the lack of enzymes affects the work of the cardiac and respiratory systems, as well as the general appearance. There are allergic reactions, peeling of the skin, the appearance of acne, foliation of nails, hair loss.

To activate and maintain the work of the pancreas, special enzyme preparations are introduced into the diet, which contribute to the absorption of food. Known means such as: pancreatin, creon, mezim, festal, cholenzim. They are used strictly on the recommendation of a doctor. At the same time, for a full recovery, it is necessary to ensure proper nutrition.

Enzymes or enzymes(from lat. fermentum - leaven) - usually protein molecules or RNA molecules (ribozymes) or their complexes that accelerate (catalyze) chemical reactions in living organisms without undergoing any changes. Substances that have a similar effect also exist in inanimate nature and are called catalysts.

Enzymatic activity can be regulated by activators and inhibitors (activators increase, inhibitors decrease chemical reactions).

The terms "enzyme" and "enzyme" have long been used interchangeably. The science of enzymes is called enzymology.

The vital activity of any organism is not possible without the participation of enzymes. Enzymatic catalysis accelerates the passage of all biochemical reactions in the body and thus provides the phenomenon of life. Without the presence of enzymes during biochemical reactions, food will not be broken down into five main compounds: carbohydrates, fats, proteins, vitamins and trace elements - food will remain useless for the body. Thus, without enzymes, life slows down.

1. stimulate the process of digestion and absorption of food;
2. activate metabolism, promote the removal of dead cells from the body;
3. regulate osmotic pressure, normalize the pH value of various media;
4. provide metabolism, support the body's ability to resist inflammatory processes;
5. increase immunity and the body's ability to self-heal and self-regulate;
6. promote detoxification of the body, cleanse the lymph and blood.

The need for enzymes for the healthy functioning of the body
Most scientists are now convinced that almost all diseases are caused by the absence or insufficient amount of enzymes in the body. Medical research shows that violations of the production of enzymes in the body are due to genetic factors.

In particular, such a common disease now as diabetes mellitus is due to the fact that the pancreas does not produce enough or does not produce the enzyme insulin at all. Leukemia and other cancers are caused by the absence or weakness of enzymatic barriers in the body. These facts are gradually confirmed by scientific research. We can say that if the body has the necessary amount of enzymes, there will not be a hundred diseases.

With age, as the human body ages, the production of enzymes decreases. The body begins to experience a lack of them, which affects the course of metabolic processes, the efficiency of digestion and absorption of nutrients decreases, it becomes more difficult to influence the body with drugs, because they are not absorbed enough and cause more side effects. The additional intake of a large number of enzymes in the body will make it possible to compensate for their deficiency and all the consequences resulting from this.

Thus, a sufficient amount of enzymes in the body is a necessary condition for its healthy state. Many diseases are caused by insufficient production of enzymes, which upsets the balance of metabolism in the body. If we provide, in addition to the natural production of enzymes, their intake from the outside, then this will be the fastest and best way to treat diseases.

The human body exists due to the constant action of enzymes. For example, in the process of digestion, with the help of enzymes (enzymes), food is decomposed into nutrients - proteins, fats, carbohydrates, vitamins and trace elements; which, with their help, are absorbed into the blood and carried to all organs. Due to this, our muscles and bones, all organs and systems are fed, receive energy and perform the functions necessary to maintain the body in a healthy, active state.

Not only the human body, but all living things, between heaven and earth, exists due to biochemical reactions carried out with the help of enzymes. The enzyme is the source of life and health of any living organism.

The role of enzymes in maintaining the vital activity of the body is surprising in its significance.

The presence of enzymes and the existence of all living things are inseparable concepts. If the amount of the enzyme is not enough to sustain life, it means death. The appearance of green leaves on trees in spring, the light of a firefly, any act of life of the human body (whether eating, walking down the street, singing, laughing or crying) - all these processes are provided by biochemical reactions and are not possible without the obligatory participation of enzymes.

From the first day of the conception of a child, enzymes begin to fulfill their role. A sperm will not be able to enter the egg if it lacks a special enzyme to dissolve the cell wall of the egg to carry out the fertilization process.

All the food we consume goes through a complex process of splitting into simple elements in the gastrointestinal tract under the influence of digestive enzymes. Only then can these nutrients enter the bloodstream and be carried to all organs and tissues. Try chewing a piece of bread for 2-3 minutes, you will feel how it gradually becomes sweet - this is because under the influence of enzymes contained in saliva, starch is broken down and sweet maltose is released.

With the help of enzymes in the body, not only the process of splitting substances takes place, but also their synthesis. For example, the synthesis of amino acids into protein molecules - the main building material for muscle cells, hair, etc., or the conversion of glucose into glycogen, which is deposited in the liver and, in case of a lack of energy, with the help of the same enzymes, is again broken down into glucose molecules , which provides the body with a rapid release of energy.

The process of skin renewal also occurs due to enzymes involved in metabolic processes. If there are enough enzymes specific for this process, the skin will be soft, shiny and elastic. With an enzyme deficiency, the skin becomes dry, flaky, and lethargic.

About 4,000 different types of enzymes function in the human body. Thousands of biochemical reactions take place in it, which together can be compared to a large chemical plant. But all these chemical reactions require enzymatic catalysis, otherwise they either do not proceed or proceed very slowly. Each enzyme participates in one chemical reaction. Some of the enzymes cannot be synthesized by the body. If the body lacks any enzymes, then there is a danger of the development of a disease or the occurrence of a pre-morbid condition, which sooner or later will manifest itself in the disease.

Therefore, if you want to maintain your youth, beauty and health for many years, you must ensure that the body contains a sufficient amount of enzymes. And if their level is low, then the main source of their replenishment is daily intake in the form of bioactive supplements.

Groups of people especially in need of additional sources of enzymes
Consider which groups of people especially need the use of additional enzymes.

Those who want to improve their physical fitness, improve their health or restore it after an illness.

Immunocompromised people, often prone to infections.

Those who experience constant fatigue complain of lack of energy, frequent weakness.

Prematurely aging, infirm people.

People suffering from chronic diseases.

Cancer patients with various types of cancer, in the pre- and postoperative period.

People suffering from liver disease.

People who prefer meat.

People prone to neurasthenia and other neuropsychiatric diseases.

People suffering from sexual dysfunction.

Women in the prenatal and postnatal period.

People with digestive disorders.

Vegetarians (nutritional supplements will promote cell stability).

People with insufficient physique, to improve physical fitness (overweight and obesity, underweight).

People with disabilities and movement restrictions.

Children in a period of intensive growth (since modern children, for the most part, almost do not consume foods containing digestive enzymes - lipase, amylase and protease; and this is one of the main causes of childhood obesity, frequent allergies, constipation, and increased fatigue).

Elderly people (with age, the body's ability to produce its own enzymes decreases, the amount of the enzyme that stimulates the "inventory" process in the body decreases, which is why the consumption of additional enzymes is the way to longevity for them).

Patients with established enzyme dysfunction (since their own enzyme stores are depleted, they especially need additional enzyme intake).

Athletes especially need a large amount of additional enzymes, because due to intense physical exertion in their body, an accelerated metabolism occurs, which means that the consumption of enzyme reserves also occurs intensely (figuratively, they can be compared with a candle burning from two ends).

Enzymes are a special type of proteins that nature has assigned the role of catalysts for various chemical processes.

This term is constantly heard, however, not everyone understands what an enzyme or enzyme is, what functions this substance performs, and also how enzymes differ from enzymes and whether they differ at all. We'll find out all this now.

Without these substances, neither humans nor animals would be able to digest food. And for the first time, mankind resorted to the use of enzymes in everyday life more than 5 thousand years ago, when our ancestors learned to store milk in "dishes" from the stomachs of animals. Under such conditions, under the influence of rennet, it turned into cheese. And this is just one example of how an enzyme works as a catalyst that speeds up biological processes. Today, enzymes are indispensable in industry, they are important for the production of leather, textiles, alcohol and even concrete. These beneficial substances are also present in detergents and washing powders - they help remove stains at low temperatures.

Discovery history

Enzyme in Greek means "sourdough". And mankind owes the discovery of this substance to the Dutchman Jan Baptist Van Helmont, who lived in the 16th century. At one time he became very interested in alcoholic fermentation and during the study he found an unknown substance that accelerates this process. The Dutchman called it fermentum, which means fermentation. Then, almost three centuries later, the Frenchman Louis Pasteur, also observing fermentation processes, came to the conclusion that enzymes are nothing but the substances of a living cell. And after some time, the German Eduard Buchner extracted the enzyme from yeast and determined that this substance is not a living organism. He also gave him his name - "zimaza". A few years later, another German, Willy Kuehne, proposed to divide all protein catalysts into two groups: enzymes and enzymes. Moreover, he proposed to call the second term “sourdough”, the actions of which extend outside living organisms. And only 1897 put an end to all scientific disputes: it was decided to use both terms (enzyme and enzyme) as absolute synonyms.

Structure: a chain of thousands of amino acids

All enzymes are proteins, but not all proteins are enzymes. Like other proteins, enzymes are made up of . And interestingly, the creation of each enzyme takes from a hundred to a million amino acids strung like pearls on a string. But this thread is not even - it is usually bent hundreds of times. Thus, a three-dimensional structure unique for each enzyme is created. Meanwhile, the enzyme molecule is a relatively large formation, and only a small part of its structure, the so-called active center, is involved in biochemical reactions.

Each amino acid is connected to a specific type of chemical bond, and each enzyme has its own unique amino acid sequence. To create most of them, about 20 types are used. Even minor changes in the amino acid sequence can dramatically change the look and feel of an enzyme.

Biochemical properties

Although a huge number of reactions occur in nature with the participation of enzymes, they can all be divided into 6 categories. Accordingly, each of these six reactions proceeds under the influence of a certain type of enzyme.

Reactions involving enzymes:

1. Oxidation and reduction.

The enzymes involved in these reactions are called oxidoreductases. As an example, remember how alcohol dehydrogenases convert primary alcohols to aldehyde.

1. Group transfer reaction.

The enzymes responsible for these reactions are called transferases. They have the ability to move functional groups from one molecule to another. This happens, for example, when alanine aminotransferases move alpha-amino groups between alanine and aspartate. Transferases also move phosphate groups between ATP and other compounds, and create them from residues.

1. Hydrolysis.

The hydrolases involved in the reaction are able to break single bonds by adding elements of water.

1. Create or remove a double bond.

This type of reaction occurs in a non-hydrolytic way with the participation of lyase.

1. Isomerization of functional groups.

In many chemical reactions, the position of the functional group changes within the molecule, but the molecule itself is made up of the same number and types of atoms that it had before the reaction began. In other words, the substrate and product of the reaction are isomers. This type of transformation is possible under the influence of isomerase enzymes.

1. The formation of a single bond with the elimination of the element water.

Hydrolases break bonds by adding water elements to the molecule. Lyases carry out the reverse reaction, removing the aqueous part from the functional groups. Thus, a simple connection is created.

How they work in the body

Enzymes speed up almost all chemical reactions that occur in cells. They are vital for humans, facilitate digestion and speed up metabolism.

Some of these substances help break down molecules that are too large into smaller "chunks" that the body can digest. Others, on the contrary, bind small molecules. But enzymes, scientifically speaking, are highly selective. This means that each of these substances is capable of accelerating only a certain reaction. The molecules that enzymes work with are called substrates. The substrates, in turn, form a bond with a part of the enzyme called the active site.

There are two principles that explain the specifics of the interaction of enzymes and substrates. In the so-called "key-lock" model, the active site of the enzyme occupies the place of a strictly defined configuration in the substrate. According to another model, both participants in the reaction, the active site and the substrate, change their shapes in order to connect.

Whatever the principle of the interaction, the result is always the same - the reaction under the influence of the enzyme proceeds many times faster. As a result of this interaction, new molecules are “born”, which are then separated from the enzyme. And the catalyst substance continues to do its job, but with the participation of other particles.

Hyper- and hypoactivity

There are times when enzymes perform their functions with the wrong intensity. Excessive activity causes excessive reaction product formation and substrate deficiency. The result is poor health and serious illness. The cause of enzyme hyperactivity can be either a genetic disorder or an excess of vitamins or used in the reaction.

Enzyme hypoactivity can even cause death when, for example, enzymes do not remove toxins from the body or ATP deficiency occurs. The cause of this condition can also be mutated genes or, conversely, hypovitaminosis and a deficiency of other nutrients. In addition, lower body temperature similarly slows down the functioning of enzymes.

Catalyst and more

Today you can often hear about the benefits of enzymes. But what are these substances on which the performance of our body depends?

Enzymes are biological molecules whose life cycle is not determined by the boundaries of birth and death. They just work in the body until they dissolve. As a rule, this occurs under the influence of other enzymes.

In the course of a biochemical reaction, they do not become part of the final product. When the reaction is complete, the enzyme leaves the substrate. After that, the substance is ready to start working again, but on a different molecule. And so it goes on for as long as the body needs.

The uniqueness of enzymes is that each of them performs only one assigned function. A biological reaction occurs only when the enzyme finds the right substrate for it. This interaction can be compared with the principle of operation of a key and a lock - only correctly selected elements can work together. Another feature: they can work at low temperatures and moderate pH, and as catalysts they are more stable than any other chemicals.

Enzymes as catalysts speed up metabolic processes and other reactions.

As a rule, these processes consist of certain stages, each of which requires the work of a certain enzyme. Without this, the transformation or acceleration cycle cannot be completed.

Perhaps the most well-known of all the functions of enzymes is the role of a catalyst. This means that enzymes combine chemicals in such a way as to reduce the energy costs required to form a product more quickly. Without these substances, chemical reactions would proceed hundreds of times slower. But the abilities of enzymes do not end there. All living organisms contain the energy they need to continue living. Adenosine triphosphate, or ATP, is a kind of charged battery that supplies energy to cells. But the functioning of ATP is impossible without enzymes. And the main enzyme that produces ATP is synthase. For each glucose molecule that is converted into energy, synthase produces about 32-34 ATP molecules.

In addition, enzymes (lipase, amylase, protease) are actively used in medicine. In particular, they serve as a component of enzymatic preparations, such as Festal, Mezim, Panzinorm, Pancreatin, used to treat indigestion. But some enzymes can also affect the circulatory system (dissolve blood clots), accelerate the healing of purulent wounds. And even in anti-cancer therapy, they also resort to the help of enzymes.

Factors that determine the activity of enzymes

Since the enzyme is able to speed up reactions many times over, its activity is determined by the so-called turnover number. This term refers to the number of substrate molecules (reactive substances) that 1 enzyme molecule can transform in 1 minute. However, there are a number of factors that determine the rate of a reaction:

1. substrate concentration.

Increasing the substrate concentration leads to an acceleration of the reaction. The more molecules of the active substance, the faster the reaction proceeds, since more active centers are involved. However, acceleration is possible only until all enzyme molecules are involved. After that, even increasing the concentration of the substrate will not accelerate the reaction.

1. Temperature.

Usually, an increase in temperature leads to an acceleration of reactions. This rule works for most enzymatic reactions, but only as long as the temperature does not rise above 40 degrees Celsius. After this mark, the reaction rate, on the contrary, begins to decrease sharply. If the temperature drops below a critical point, the rate of enzymatic reactions will increase again. If the temperature continues to rise, the covalent bonds are broken and the catalytic activity of the enzyme is lost forever.

1. Acidity.

The rate of enzymatic reactions is also affected by the pH value. Each enzyme has its own optimal level of acidity, at which the reaction proceeds most adequately. Changing the pH level affects the activity of the enzyme, and hence the rate of the reaction. If the change is too great, the substrate loses its ability to bind to the active nucleus, and the enzyme can no longer catalyze the reaction. With the restoration of the required pH level, the activity of the enzyme is also restored.

Enzymes present in the human body can be divided into 2 groups:

• metabolic;
• digestive.

Metabolic "work" to neutralize toxic substances, and also contribute to the production of energy and proteins. And, of course, they accelerate the biochemical processes in the body.

What the digestive organs are responsible for is clear from the name. But even here the principle of selectivity works: a certain type of enzyme affects only one type of food. Therefore, to improve digestion, you can resort to a little trick. If the body does not digest something from food well, then it is necessary to supplement the diet with a product containing an enzyme that can break down hard-to-digest food.

Food enzymes are catalysts that break down food to a state in which the body is able to absorb useful substances from them. Digestive enzymes come in several types. In the human body, different types of enzymes are found in different parts of the digestive tract.

Oral cavity

At this stage, alpha-amylase acts on the food. It breaks down carbohydrates, starches and glucose found in potatoes, fruits, vegetables and other foods.

Stomach

Here, pepsin breaks down proteins into peptides, and gelatinase breaks down the gelatin and collagen found in meat.

Pancreas

At this stage, "work":

• trypsin - responsible for the breakdown of proteins;
• alpha-chymotrypsin - helps the absorption of proteins;
• elastase - break down certain types of proteins;
• nucleases - help break down nucleic acids;
• steapsin - promotes the absorption of fatty foods;
• amylase - responsible for the absorption of starches;
• lipase - breaks down fats (lipids) found in dairy products, nuts, oils, and meats.

Small intestine

Over food particles "conjure":

• peptidases - break down peptide compounds to the level of amino acids;
• sucrase - helps to absorb complex sugars and starches;
• maltase - breaks down disaccharides to the state of monosaccharides (malt sugar);
• lactase - breaks down lactose (glucose found in dairy products);
• lipase - promotes the absorption of triglycerides, fatty acids;
• erepsin - affects proteins;
• isomaltase - "works" with maltose and isomaltose.

Colon

Here the functions of enzymes are performed:

• coli - responsible for digestion;
• lactobacilli - affect lactose and some other carbohydrates.

In addition to these enzymes, there are also:

• diastase - digests vegetable starch;
• invertase - breaks down sucrose (table sugar);
• glucoamylase - converts to glucose;
• alpha-galactosidase - promotes the digestion of beans, seeds, soy products, root vegetables and leafy vegetables;
• bromelain - an enzyme derived from, promotes the breakdown of different types of proteins, is effective at different levels of acidity of the environment, and has anti-inflammatory properties;
• papain, an enzyme isolated from raw papaya, promotes the breakdown of small and large proteins, and is effective over a wide range of substrates and acidity.
• cellulase - breaks down cellulose, plant fibers (not found in the human body);
• endoprotease - cleaves peptide bonds;
• ox bile extract - an enzyme of animal origin, stimulates intestinal motility;
• pancreatin - an enzyme of animal origin, accelerates the digestion of proteins;
• pancrelipase - an animal enzyme that promotes the absorption

  Fermented foods are a near-perfect source of beneficial bacteria needed for proper digestion. And while pharmacy probiotics "work" only in the upper digestive system and often do not reach the intestines, the effect of enzymatic products is felt throughout the gastrointestinal tract.

  For example, apricots contain a mixture of beneficial enzymes, including invertase, which is responsible for the breakdown of glucose and promotes rapid energy release.

  A natural source of lipase (promotes faster digestion of lipids) can serve. In the body, this substance is produced by the pancreas. But in order to make life easier for this body, you can treat yourself, for example, to a salad with avocado - tasty and healthy.

  In addition to being perhaps the most famous source, it also supplies amylase and maltase to the body. Amylase is also found in bread and cereals. Maltase aids in the breakdown of maltose, the so-called malt sugar, which is abundant in beer and corn syrup.

  Another exotic fruit - pineapple contains a whole range of enzymes, including bromelain. And it, according to some studies, also has anti-cancer and anti-inflammatory properties.

  Extremophiles and industry

  Extremophiles are substances that can survive in extreme conditions.

  Living organisms, as well as the enzymes that enable them to function, have been found in geysers where the temperature is close to the boiling point, and deep in ice, as well as in conditions of extreme salinity (Death Valley in the USA). In addition, scientists have found enzymes for which the pH level, as it turned out, is also not a fundamental requirement for effective work. Researchers are studying extremophile enzymes with particular interest as substances that can be widely used in industry. Although even today enzymes have already found their application in the industry as biologically and environmentally friendly substances. The use of enzymes is resorted to in the food industry, cosmetology, and the production of household chemicals.

  Izvozchikova Nina Vladislavovna

  Speciality: infectious disease specialist, gastroenterologist, pulmonologist.

  General experience: 35 years .

  Education:1975-1982, 1MMI, San-Gig, highest qualification, infectious diseases doctor.

  Science degree: doctor of the highest category, candidate of medical sciences.