What is the main consequence of phosphorylating ACC2 at residue 212?

• A. Inactivation of the enzyme
• B. Activation of fatty acid oxidation
• C. Increased fatty acid synthesis
• D. Decreased insulin secretion

Answer: (A)

Phosphorylation of ACC2 (acetyl-CoA carboxylase 2) at residue 212 leads to the inactivation of the enzyme. ACC2 plays a crucial role in the regulation of fatty acid metabolism by catalyzing the carboxylation of acetyl-CoA to malonyl-CoA, the key precursor for fatty acid synthesis. When ACC2 is phosphorylated at this specific residue, it undergoes conformational changes that reduce its enzymatic activity, effectively inhibiting the synthesis of malonyl-CoA. This reduction in malonyl-CoA levels decreases the inhibition of fatty acid oxidation, thereby promoting the breakdown of fatty acids for energy.

In the context of metabolic regulation, this phosphorylation event serves as a signal to decrease fatty acid synthesis while allowing fatty acid oxidation to proceed, reflecting the body's needs for energy under different physiological conditions. Therefore, inactivation of ACC2 through phosphorylation is a critical regulatory mechanism in maintaining metabolic balance.