[Mechanism of the reaction catalyzed by glycogen synthetase I in rabbit skeletal muscle].

1.5-Gluconolactone was shown to exert a strong inhibiting effect on the activity of rabbit skeletal muscle glycogen synthase I. The Ki values determined according to Dixon (0.13 mM) and Chuang and Bell (0.14 mM) coincide with the Km value for UDPG. Within the pH range of 5.4-7.0, N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide (less than or equal to 3 mM) specifically inhibits the carboxyl group, which was supported by the reactivation of the enzyme under mild alkaline conditions. The reversible competitive inhibitor of glycogen synthase and the UDP reaction product as well as 1.5-gluconolactone afford an effective protective effect. It is supposed that the reaction catalyzed by rabbit skeletal muscle glycogen synthase I results in the formation of an intermediate carbonium ion. An essential role in the enzyme activity belongs to the carboxylic group of the active center.