Total conversion of glycogen synthase from the I- to the D-form by a cyclic AMP-independent protein kinase from rabbit skeletal muscle.
A newly discovered cyclic AMP-independent protein kinase, which catalyzes the total conversion of glycogen synthase from the I- to the D-form, has been isolated from rabbit skeletal muscle. This enzyme, designated glycogen synthase kinase, is separable from cyclic AMP-dependent protein kinase by column chromatography on phosphocellulose. Synthase kinase and cyclic AMP-dependent protein kinase are distinct in their specificity for protein substrates, the effects of cyclic AMP and the inhibitor of cyclic AMP-dependent protein kinase on their activities, and the extent to which they phosphorylate I-form glycogen synthase. The phosphorylation of I-form enzyme by synthase kinase results in the incorporation of 4 mol of phosphate/85,000 subunit; however only two of the phosphate sites seem predominantly to determine glucose-6-P dependence. The resulting multiply phosphorylated enzyme, which is highly dependent on glucose-6 P for activity, has a phosphate content comparable to the D-form enzyme isolated from rabbit muscle.
D000818:Animals; D000242:Cyclic AMP / Q000494:pharmacology; D004789:Enzyme Activation; D006006:Glycogen Synthase / Q000378:metabolism*; D007700:Kinetics; D008970:Molecular Weight; D009132:Muscles / Q000201:enzymology*; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism*; D011817:Rabbits
D000242:Cyclic AMP; D006006:Glycogen Synthase; D011494:Protein Kinases