Ca2+-stimulated phosphorylation of muscle glycogen synthase by phosphorylase b kinase.
Phosphorylase b kinase from rabbit muscle phosphorylates glycogen synthase purified from the same tissue. The reaction is markedly stimulated by Ca2+ and results in a decrease in the synthase %I activity. Phosphorylase b kinase action leads to the incorporation of phosphate (0.6 to 0.8 mol/mol of subunit) preferentially into a single cyanogen bromide fragment of synthase (fragment III). Cyclic AMP-independent synthase kinase also shows a specificity for the site(s) contained in fragment III whereas the cyclic AMP-dependent protein kinase exerts a preference for the site(s) located in a distinct cyanogen bromide fragment (fragment II). A Ca2+-stimulated endogenous kinase also results in the phosphorylation of fragment III and can be attributed to the presence of phosphorylase b kinase. The finding of a Ca2+-stimulated phosphorylation of glycogen synthase has important implications for the regulation of glycogen metabolism and particularly those processes thought to be controlled by cytoplasmic Ca2+ concentration.
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D006006:Glycogen Synthase / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D009132:Muscles / Q000201:enzymology*; D010764:Phosphorylase Kinase / Q000378:metabolism*; D010766:Phosphorylation; D010774:Phosvitin / Q000378:metabolism; D011817:Rabbits; D013268:Stimulation, Chemical; D013379:Substrate Specificity
D006657:Histones; D010774:Phosvitin; D006006:Glycogen Synthase; D010764:Phosphorylase Kinase; D002118:Calcium