Final answer:
Protein phosphatase 1 (PP1) is the enzyme responsible for dephosphorylating and activating glycogen phosphorylase, which is a key enzyme in glycogenolysis.
Step-by-step explanation:
The enzyme responsible for dephosphorylating, and thereby activating, glycogen phosphorylase is protein phosphatase 1 (PP1). Glycogen phosphorylase plays a crucial role in glycogenolysis - the process of breaking down glycogen into glucose. This enzyme is responsible for catalyzing the release of glucose-1-phosphate from glycogen, but it requires activation through phosphorylation.
When the body needs to mobilize stored glycogen, hormones like epinephrine and glucagon trigger a cascade of reactions leading to the phosphorylation and activation of glycogen phosphorylase. This process involves the conversion of inactive phosphorylase b to its active form, phosphorylase a, accomplished by phosphorylase kinase. To reverse this process and deactivate glycogen phosphorylase, protein phosphatase 1 removes the phosphate group, converting phosphorylase a back into the inactive form, phosphorylase b.