Harpers

Epinephrineβ Receptor+InactiveadenylylcyclaseActiveadenylylcyclaseATP+cAMPPHOSPHODIESTERASE5′-AMPGlycogen (n+1)Glycogen (n)+Glucose 1-phosphate+149Inhibitor-1(inactive)InactivecAMP-DEPENDENTPROTEIN KINASEATPActivecAMP-DEPENDENTPROTEIN KINASECALMODULINCOMPONENT OFPHOSPHORYLASEKINASEADPP iADPPHOSPHORYLASE a(active)H 2 OATPPHOSPHORYLASE KINASE b(inactive)Ca 2+PHOSPHORYLASE KINASE a(active)–G6P+InsulinPROTEINPHOSPHATASE-1ADP+P i–Ca 2+PROTEINPHOSPHATASE-1H 2 OATPPHOSPHORYLASE b(inactive)P i–Inhibitor-1-phosphate(active)–Figure 18–6. Control of phosphorylase in muscle. The sequence of reactions arranged as a cascade allows amplification of the hormonal signalat each step. (n = number of glucose residues; G6P, glucose 6-phosphate.)