Carbohydrate Metabolism Regulation Problem Set

Question 5: Enzyme Phosphorylation Induced by Glucagon

The same enzymes that are dephosphorylated by insulin action (namely glycogen synthase, glycogen phosphorylase, the PFK-2/FBPase-2 bifunctional enzyme and pyruvate kinase) are phosphorylated via glucagon and/or epinephrine action. Which kinase is responsible for these phosphorylation events?

A.	Protein kinase C
B.	Calmodulin-dependent kinase
C.	Protein kinase A This is a very clear example of how glucagon and epinephrine oppose the actions of insulin. Also, the general rule that insulin promotes dephosphorylation, while glucagon promotes phosphorylation via cAMP/protein kinase A, will hold up very well throughout the course.
D.	Receptor tyrosine kinase
E.	b-ARK