Biochemistry

structure of the enzyme occur, leading to a successive approach to the substrate and spatial orientation of those active groups that interact with each other at different stages of substrate transformation. A change in the tertiary structure of the protein is possible only with the participation of the entire (or almost all) polypeptide chain forming the protein molecule. Therefore, the whole enzyme molecule takes part in the catalytic process with the ordered interaction of its centers, which ensures the sequential implementation of multi-stage processes of enzymatic catalysis. The direction of the reactions depends on the change in energy during the reaction, on the difference between the free energies of the starting andforming substances. There is another feature of the action of enzymes: in the body, the conversion of substances to final products occurs in several stages, each of which is catalyzed by a separate enzyme. For example, the synthesis of fatty acids is provided by a group of enzymes, which includes seven enzymes. The sum of the activation energy of the intermediate reactions is lower than the activation energy requiredfor the simultaneous cleavage of the substrate. Adsorption theory. According to this theory, reacting substances are adsorbed on the surface of the enzyme, which contributes to an increase in their concentration, the convergence of reactive groups of reacting particles. Substances that are on the surface of the enzyme (adsorbent) can be retained due to simple physical adsorption, due to the forces of intermolecular interaction and a stronger chemical bond. The catalyst by its force field causes certain changes in the structure of the reacting substances, which leads to an increase in the reactivity of the substrate and an increase in the reaction rate. Among such changes, the formation of a complex consisting of an enzyme and a substrate occupies an important place. The formation of intermediate compounds of the catalyst with the substrate and the subsequent decomposition of this complex. In this case, the enzyme is regenerated, and the substrate is modified. Intermediate reactions require much less activation energy than a reaction without a catalyst. They go much faster, so the speed of the total reaction increases. Each enzyme contains certain chemical groups, due to which it enters into a connection with the substrate and carries out its catalytic effect. Such groups are SH-groups, residues of histidine, serine, tyrosine, etc. These groups are located in different sites in the enzyme molecule, but interact with each other and are responsible for the catalytic activity of the enzyme. These groups are called functional groups of enzymes. In the enzyme molecule, there is a combination of various chemical groups forming the active center in the enzyme molecule, due to which its catalytic effect is realized. 91