<prompt> In muscle, Phosphorylase a is inactivated bycAMPCa2 ionGlucoseATP  <response>: In the liver, the role of glycogen is to provide free glucose for export to maintain the blood concentration of glucose. In muscle the role of glycogen is to provide a source of glucose-6-phosphate for glycolysis in response to the need for ATP for muscle contraction.In both tissues, the enzyme is activated by phosphorylation catalyzed by phosphorylase kinase to yield phosphorylase a and inactivated by dephosphorylation catalyzed by phosphoprotein phosphatase to yield phosphorylase b, in response to hormonal and other signals.There is instantaneous overriding of this hormonal control. Active phosphorylase a in both tissues is allosterically inhibited by ATP and glucose-6-phosphate; in liver, but not muscle, free glucose is also an inhibitor.Harper 30th edition page 179 