Conversion of glycogen phosphorylase b to a by non-activated phosphorylase b kinase: an in vitro model of the mechanism of increase in phosphorylase a activity with muscle contraction.
Phosphorylase b kinase activity, as present in resting muscle in the non-activated form, appears to be ample to account for the fast appearance of phosphorylase a observed with muscle contraction. The kinase activity is repressed by free ATP and stimulated by free Mg(2+). Phosphorylase b kinase activity increases greatly when the Mg(2+):ATP ration exceeds 1. It is proposed that the breakdown of ATP that occurs during muscle contraction may represent the triggering factor for the observed in vivo conversion of phosphorylase b into a.
D000255:Adenosine Triphosphate; D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D000242:Cyclic AMP; D003864:Depression, Chemical; D004789:Enzyme Activation; D004794:Enzyme Repression; D005964:Glucosyltransferases; D008274:Magnesium; D008954:Models, Biological; D009119:Muscle Contraction; D009132:Muscles / Q000201:enzymology; D010764:Phosphorylase Kinase; D011817:Rabbits; D013268:Stimulation, Chemical
D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D005964:Glucosyltransferases; D010764:Phosphorylase Kinase; D008274:Magnesium