Stimulation of glycogen synthase phosphorylation by calcium-dependent regulator protein.
Phosphorylation of skeletal muscle glycogen synthase catalyzed by a protein kinase is stimulated up to 10-fold by the calcium-dependent regulator (CDR) protein. Half-maximal stimulation requires about 1 microgram of CDR/ml. Phosphorylation by the CDR-dependent synthase kinase is more rapid at pH 8.6 than at pH 6.8 and is blocked by ethylene glycol bis(beta-aminoethyl-ether)N,N'-tetraacetic acid and trifuloperazine. Approximately 60 to 70% of the phosphate is incorporated into the trypsin-insensitive region of glycogen synthase resulting in conversion of the a form to the b form of the enzyme. The CDR-dependent synthase kinase is not myosin light chain kinase, as this enzyme does not phosphorylate glycogen synthase. Furthermore, synthase phosphorylation by the cAMP-dependent protein kinase catalytic subunit is not affected by CDR. The possibility that CDR-dependent synthase kinase may be phosphorylase kinase is being investigated.
D000818:Animals; D002147:Calmodulin / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D006006:Glycogen Synthase / Q000378:metabolism*; D007700:Kinetics; D009132:Muscles / Q000201:enzymology; D009218:Myosins; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*
D002147:Calmodulin; D002352:Carrier Proteins; D006006:Glycogen Synthase; D011494:Protein Kinases; D009218:Myosins