Biochemistry

associated with a violation or lack of synthesis of specific enzymes; their introduction into the complex of therapeutic agents compensates for the discovered shortcomings. In their action, biological catalysts - enzymes - differ from catalysts of inanimate nature. Being proteins, they have a complex structure, while many inorganic catalysts are low molecular weight substances. Enzymes are characterized by very high activity. The enzymatic reaction proceeds 10 6 -10 12 times faster than the spontaneous non-catalyzed reaction in an aqueous solution. In living organisms, in the presence of enzymes, complex reactions, ordered in time and space, can be carried out in fractions of a second, which would take days, weeks, and even months to carry out under laboratory conditions. So, 1 g of pepsin, an enzyme of gastric juice that catalyzes the digestion of proteins, can hydrolyze 100 kg of egg white at 1 hour. Enzyme-catalyzed reactions, unlike many chemical reactions of organic substances carried out under laboratory conditions, proceed without the formation of by-products, with almost 100 percent yield. All enzymes exhibit their activity under relatively mild conditions: at a moderate temperature (25-40 °C), normal pressure, at a low concentration of hydrogen ions, i.e. in conditions when the chemicals that make up the body are converted very slowly without a catalyst. As the Swedish chemist J.Ya.Berzelius pointed out, in order to hydrolyze starch to glucose outside the body, it is necessary to heat this polysaccharide in an acid solution for several hours, and with the participation of the corresponding enzyme, this process occurs at room temperature and lasts only a few minutes. The next significant difference between enzymes and inanimate catalysts is their specificity with respect to the type of reaction and to substances in which the process of change is accelerated by this enzyme. Enzymes in the cell are precisely localized. The strict correspondence of biochemical processes to the organelles of the cell determines the localization of certain individual enzymes, multienzyme complexes — polyenzyme blocks. For example, in mitochondria, complexes of redox enzymes are concentrated, in ribosomes - enzymes involved in protein biosynthesis, in lysosomes - hydrolases, in protoplasm - enzymes that activate amino acids, in the nuclear apparatus of the cell - mainly enzymes that carry out biosynthesis of nucleic acids. Owing to such localization of enzyme systems, the catalysis process is a series of successive elementary transformations of substances that are most strictly coordinated and organized in space and time. As a result of this, individual cycles cover a wide range of reactions of transformations of substances in the body (oxidation and reduction, isomerization, hydrolysis, etc.), thereby ensuring the vital activity of cells, tissues, organs and the body as a whole. 79