[Inhibition of muscle glycogen phosphorylase b by heterocyclic vitamins and coenzymes]

Inhibition of rabbit skeletal muscle glycogen phosphorylase b by biotin, pyridoxine, lipoic acid, as well as by thiamine and cobalamine vitamins and coenzymes has been found. The values of "half-saturation" concentration and Hill coefficients are determined for biotin (27 mM, 1.3), pyridoxine (19 mM, 1.7), 5'-deoxyadenosyl-cobalamine (2.5 mM, 1.5), lipoic acid (3.4 mM, 1.1), thiamine (11 mM, 1.3), thiamine diphosphate (11 mM, 1.0). Effectiveness of the enzyme inhibition by vitamins and coenzymes containing different heterocyclic groups is analysed; riboflavin and its coenzymic forms are suggested to be the most effective inhibitors.