Phosphorylase B in the muscle is normally kept in inhibited state by which one of the following?
A. ATPB. AMP
C. Ca2
D. Glucose
Ans. B. (AMP)
Explanation
Muscle Phosphorylase: This exists in an active ‘a’ form and an inactive ‘b’ form. Phosphorylase is a dimmer containing two identical subunits and occurs tightly bound to glycogen granules; ‘a’ is the phosphorylated form and ‘b’ the dephosphorylated form.
Muscle Phosphorylase: This exists in an active ‘a’ form and an inactive ‘b’ form. Phosphorylase is a dimmer containing two identical subunits and occurs tightly bound to glycogen granules; ‘a’ is the phosphorylated form and ‘b’ the dephosphorylated form.
•
Phosphorylation requires ATP and occurs at the —OH groups of serine in each
subunit of the ‘b’ form to produce the ‘a’ form. This phosphorylation is
brought about by the enzyme phosphorylase kinase. In presence of AM the muscle
phosphorylase remains in inactive form.
•
Presence of Ca2 leads to activation of phosphorylase kinase which leads to
subsequent activation of muscle glycogen phosphorylase.
