Enzymes (enzymes) are high - molecular organic compounds of protein nature, which perform in the body as a biological catalysts.
The Mechanism of action of enzymes.
Elucidation of the mechanisms underlying the catalytic action of enzymes is one of the fundamental tasks and actual problems not only Enzymology, but modern molecular biochemistry and biology.
Long before the net became available enzymes and were found in their nature, there was a belief that it is crucial for the implementation of enzymatic process is the coupling of the enzyme with the substrate. Attempts to detect complex compound of the enzyme with the substrate for a long time did not lead to success, since such a complex is unstable, it quickly falls apart. Using the method of spectroscopy gave the possibility to identify the enzyme-substrate complexes of catalase, peroxidase, alcohol dehydrogenase, flavissima enzymes.
X-ray diffraction Method allowed us to obtain many important information on the structure and catalytic mechanisms of enzymes action. This method was used to establish a relationship of analogues of substrate with the enzyme lysozyme and chymotrypsin.
Some direct evidence of the existence of enzyme-substrate complexes were able to obtain for cases where one of the stages of the catalytic cycle the enzyme is bound with substrate by a covalent bond. As example is the hydrolysis reaction of n-nitrophenylacetate, catalyzed by chymotrypsin. When mixing the enzyme with this air chymotrypsin acetylated at the hydroxyl group of the reactive serine residue. This stage proceeds quickly, but hydrolysis of acetylhydrazine with the formation of acetate and free chymotrypsin is much slower. Therefore, in the presence of n-nitrophenylacetate accumulates acetylcystein, which is easy to detect.
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The Presence of the substrate in the composition of the enzyme can be “catch” by transfer of an unstable complex of the EU in an inactive form, for example, processing the enzyme-substrate complex of the borohydride of sodium, has a strong regenerative effect. A similar complex in the form of a stable covalent derivative was detected in the enzyme aldolase. It turned out that a molecule of substrate interacts with the e-amino group of lysine.
The Substrate interacts with the enzyme in a specific part called the active site, or active zone of the enzyme.
Under the active center or active area, you know that part of the enzyme protein molecule that combines with a substrate (and cofactors) and determines the enzymatic properties of the molecule. The active site determines the specificity and catalytic activity of the enzyme and needs to consist of a structure of certain complexity, adapted for close approach and interaction with the substrate molecule or its parts directly involved in the reaction.
Among the functional groups distinguish included in the “catalytically active” section of the enzyme and forming a plot providing specific affinity (binding of substrate with enzyme) — the so-called pin, or “anchor” (or adsorption section of the active center of the enzyme).
The Mechanism of action of enzymes explains the theory of Michaelis-cement. According to this theory, the process occurs in four stages.
The Mechanism of action of enzymes: phase I
Between the substrate (s) and enzyme (E) there is a connection – forms enzyme-substrate complex of the EU, in which the components are linked covalent, ionic, water, and other links.
The Mechanism of action of enzymes: phase II
The Substrate under the influence of the attached enzyme is activated and becomes available for the corresponding reactions of catalysis of the EU.
The Mechanism of action of enzymes: III stage
Performed the catalysis of the EU. This theory was confirmed by experimental studies.
And finally, stage IV is characterized by the release of a molecule of enzyme E, and reaction products of R. a Sequence of transformations can be displayed as: E+With – the EU – EU* - E+R.
The Specificity of action of enzymes.
Each enzyme acts on a specific substrate or a group of substances that are similar in structure. The specificity of action of enzymes is due to the similarity of the configuration of the active center and substrate. In the process of interaction forms enzyme-substrate complex.
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