Question

Glycogen phosphorylase activity is regulated by the phosphorylation state (phosphorylation of Ser 14). What enzyme is responsible for phosphorylation, and thereby activating, glycogen phosphorylase?

A. protein kinase A
B. protein phosphatase 1
C. glycogen debranching enzyme
D. phosphorylase kinase

Answer 1

Phosphorylase kinase is the enzyme responsible for phosphorylating and activating glycogen phosphorylase, which leads to the breakdown of glycogen into glucose-1-phosphate. The correct option is D.

Step-by-step explanation:

The enzyme responsible for phosphorylating and activating glycogen phosphorylase is phosphorylase kinase.

Glycogen phosphorylase is regulated by the phosphorylation state of serine 14. When phosphorylase kinase adds a phosphate group to serine 14, it activates glycogen phosphorylase, leading to the breakdown of glycogen into glucose-1-phosphate.

This process is regulated by various hormones, such as epinephrine and glucagon, which activate adenyl cyclase and increase the levels of cyclic AMP. Cyclic AMP then activates protein kinase A, which phosphorylates and activates phosphorylase kinase, ultimately leading to the activation of glycogen phosphorylase. Option D. is the correct one.