Sequence of events in glycogenolysis?: (A) Phosphorylase, Glucan transferase , Debranching, Phosphorylase, (B) Debranching, Phosphorylase, transferase, phosphorylase, (C) Transferase , phosphorylase, Debranching, phosphorylase, (D) Any of the above
Answer is A. A i.e. Phosphorylase, Glucan transferase, Debranching, Phosphorylase- In well fed state (also called absorptive stage) insulin suppresses glucose -6- phosphatase activity and causes glucose 6 -phosphate to enter glycogenesisR (to form glycogen).- Active glycogen phosphorylase a in both tissues (i.e. muscle and liver) is allosterically inhibited and inactivated by ATP and glucose 6- phosphateQ. Whereas in liver, but not in muscle, free glucose is also an inhibitors.Actually when phosphorylase b is activated it is called phosphorylase a.- Phosphorylase kinase exists in 2 forms - an active phosphorylated 'a' form and inactive dephosphorylated 'b' form. Active CAMP dependent protein kinase phosphorylates inactive b form to active a form. The phosphorylated enzyme can be inactivated by hydrolytic removal of phosphate by protein phosphatase 1. This enzyme is activated by kinase mediated signal cascade initiated by insulinQ.