Glycogen synthetase activity in the sea mussel (Mytilus edulis, L.)

Abstract

Glycogen Synthetase Activity in the Sea Mus­ sel (Mytilus edulis, L). Rev. esp. Fisiol., 30, 9-14. 1974.

The existence of UDPG-dependent glycogen synthetase activity has been determined in the sea mussel. The enzyme, strongly activated by Glucose-6-phosphate and prac­ tically dependent on this cofactor for activity, was inhibited by calcium ions. The Km value obtained for UDPG was about 3 X 10-4 M, and the Ka values determined for the glucose-6-phosphate depended upon the UDPG concentration, showing a coope­ rative effect between the substrate and the activator; these Ka values ranged from 9.2 X 10_s to 3.6 X 10"‘ M with concentrations of UDPG from 0.7 to 3 mM.

The optimum assay conditions were temperature 25° C and pH 7.8. The sea mus­ sel’s glycogen synthetase was widely distributed in all studied tissues and organs, and its activity was related more to their real metabolic role than to their glycogen content. The enzyme in our homogenate preparations was fairly unstable, showing a rapid time and temperature-dependent irreversible inactivation.