The action effected by protein kinase A is terminated by
A) inactivation of the initial receptor.
B) inactivation of the stimulatory G protein.
C) degradation of cAMP.
D) dephosphorylation of phosphoproteins by protein phosphatase 1.

Question

Quizplus · Accepted Answer

Protein kinase A phosphorylates various proteins to affect cellular responses. To terminate the action, the phosphoproteins need to be dephosphorylated. This is achieved by a phosphatase enzyme, such as protein phosphatase 1. Inactivation of the receptor or G protein would prevent further activation of protein kinase A, but it would not terminate the action of the kinase that already occurred. Degradation of cAMP would also have no effect on the phosphoproteins that were already phosphorylated by protein kinase A.

The Action Effected by Protein Kinase a Is Terminated by