Stimulation of autophosphorylation of rabbit skeletal muscle phosphorylase kinase by glycogen synthase on glycogen particles.

Glycogen synthase stimulated the autophosphorylation and autoactivation of phosphorylase kinase from rabbit skeletal muscle. This stimulation was additive to that by glycogen and the reaction was dependent on Ca2+. The effect by glycogen synthase was maximum within the activity ratio (the activity of enzyme without glucose-6-P divided by the activity with 10 mM glucose-6-P) of 0.3 and over 0.3 it was rather inhibitory. The results suggest that autophosphorylation of phosphorylase kinase in the presence of glycogen synthase on glycogen particles may be an important regulatory mechanism of glycogen metabolism in skeletal muscle.