Which of the Following Statements Regarding Phosphorylation of Acetyl-CoA Carboxylase

Question

Which of the following statements regarding phosphorylation of acetyl-CoA carboxylase is correct?
A) phosphorylation causes activation only in the presence of palmitoyl-CoA
B) phosphorylation is a result of glucagon binding to its receptor
C) high [citrate] inhibits the phosphorylated form
D) phosphorylation causes separation of the polymeric form of the enzyme to inactive protomers
E) both b and d are true

Accepted Answer

Phosphorylation of acetyl-CoA carboxylase is a regulatory mechanism that is influenced by hormonal signals and energy status of the cell. Glucagon, a hormone that signals low energy status or low glucose levels, activates a signaling cascade that leads to the phosphorylation of acetyl-CoA carboxylase. This phosphorylation causes the enzyme, which normally functions as an active polymer, to dissociate into inactive protomers, thus inhibiting the biosynthesis of fatty acids when energy is scarce.