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Q48 Single choice

Glucagon binding to liver cells induces an increase in intracellular cAMP concentration. The rate-limiting step in cholseterol biosynthesis is regulated as a consequence of this glucagon-mediated rise in cAMP.
The effect of increased cAMP on the rate of cholesterol biosynthesis occurs because of which of the following?

A
AMP-activated protein kinase (AMPK) is activated and directly phosphorylates human menopausal gonadotropin (HMG)-CoA reductase, leading to an increase in the activity of the latter enzyme.
B
Cyclic AMP-dependent protein kinase (PKA) is activated and directly phosphorylates HMG-CoA reductase, reducing the activity of the latter enzyme.
C
PKA is activated and phosphorylates AMP-regulated kinase, which then phosphorylates and activates HMGCoA reductase.
D
Removal of phosphate from HMG-CoA reductase increases its activity. Activated PKA results in a reduced level of phosphate removal from HMG-CoA reductase so that the latter enzyme is kept less active.
E
The increased cAMP directly inhibits HMG-CoA reductase.

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