Biochemistry

metabolic processes catalyzed by enzymes is carried out by hormones and other regulatory factors, the formation and activity of which are controlled by the nervous system. 3.6 NOMENCLATURE AND CLASSIFICATION OF ENZYMES The current nomenclature and classification of enzymes was approved in 1961 at the V International Biochemical Congress in Moscow. The basis of the creation of the nomenclature was the following principles: a) the end of -ase should be used only for simple enzymes-, for multienzyme complexes, the term system is recommended (for example, the pyruvate dehydrogenase system); b) the name should reflect the reaction mechanism, the name of the substrate and coenzyme, the type of reaction catalyzed. Given these rules, instead of the previous name, for example, “ lactate dehydrogenase ” , the systematic name lactate-NAD-oxidoreductase is recommended, which contains three positions: the substrate is lactate (lactic acid), the coenzyme is NAD (nicotinamide adenine dinucleotide), the enzyme oxidoreductase catalyzes the transfer of hydrogen from the substrate to the acceptor, i.e., the type of reaction is indicated. All enzymes are divided into six classes: oxidoreductases, transferases, hydrolases, lyases, isomerases, ligases (synthetases) . Each class has subclasses. Oxidoreductases. All enzymes (dehydrogenases, oxidases, etc.) that catalyze oxidative-reducing reactions are assigned to this class. These reactions are carried out by a chain of enzymes and intermediate carriers of hydrogen or electrons from the primary substrate to the final acceptor - oxygen. A feature of oxidoreductases is their ability to accelerate a large number of a wide variety of redox reactions, which provides a coenzyme compound with many apoenzymes. In this case, an oxidoreductase specific for one or another substrate is formed each time. Oxidoreductases are involved in chemical reactions associated with the release of energy. Transferase. Enzymes of this class carry out intramolecular and intermolecular transfer of individual functional groups. Depending on the nature of the moieties transferred, methyltransferases are distinguished — methyl groups — CH 3 are transferred, aminotransferases — amine groups — NH 2 are transferred, phosphotransferases — the remainder of phosphoric acid is transported. Hydrolases. Enzymes of this class provide splitting of intramolecular bonds of organic compounds at the participation of water. A large group of enzymes belongs to this class, including almost all enzymes of the gastrointestinal tract: esterase, phosphatase, peptidase, etc. • sJ. 94