Biochemistry

stabilizes the protein part, making it more resistant to the effects of denaturing substances. Coenzyme can easily be separated from the apoenzyme and “ serve ” two or more enzymes, as well as exist independently. One and the same coenzyme, joining different proteins, can catalyze completely different reactions. So, in one reaction, pyridoxalphosphate (vitamin B 6 ) accelerates transamination, and in the other, decarboxylation of amino acids. Coenzyme is connected to the apoenzyme by bonds of different strengths. The prosthetic group is inseparable from the protein part of the enzyme. The role of coenzymes in complex enzymes is performed by most vitamins (Bi, B 2 , B 3 , B 4 , B 5 , B 6 , Bn, B c , H, etc.) or compounds that include vitamins, metal ions, etc. For example, vitamin H is included in the composition of cocarboxylases that catalyze the biosynthesis of higher fatty acids, as it promotes the assimilation of carbon monoxide. Coenzyme A or coenzyme A (CoA and HSKoA) contains pantothenic acid (vitamin B 3 ). Given the structural features of CoA, it is also called adenine pantotheyl dinucleotide. The reactive part of CoA is the HS-group of mercaptoethylamine'. 0 -Mercapto ethylamine p-Alania Pantothenic acid 0 (1 Q II я HS-CH^CH-NH •C-CH j -CH j -NH i HC-CH- 1 -C-CH- o-p- 1 OH CH 3 OH Along with vitamins, some peptides can perform the coenzyme function, for example, HS-glutathione (ү -glutaminylcysteinyl-glycine), which is involved in redox processes, as well as a large group of nucleotides. The coenzyme may be esters of certain monosaccharides, lipoic acid, and a number of other substances. In cases where metal ions are part of the cofactor, they serve as a bridge that binds the enzyme to the substrate, resulting in the formation of a coordination complex. Metal ions can also be in the structure of the active center, where they are directly involved in catalysis (for example, in catalase, peroxidase, cytochrome oxidase). In the table. 3.1 provides a classification of the most common coenzymes by their chemical structure. 81