On the process of activation and inactivation of dog skeletal muscle glycogen synthase

The presence of additional forms of glycogen synthase (UDPG: alpha-1,4-glucan alpha-4-glucosyltransferase) besides the I form (independent on glucose-6-P for activity) and the D form (dependent on glucose-6-P for activity) long ago described, is inferred from patterns of their interconversions obtained by processes of phosphorylation and dephosphorylation. An intermediate form more phosphorylated than the I form and less than the D form, which is completely inactive in these assay conditions, and a superphosphorylated form, more phosphorylated than the D form and also inactive even in presence of 0.01 M glucose-6-P are described.