What is the primary metabolic function of acetyl-CoA carboxylase (ACC)?

Study for the Biochemistry Module 6 Exam. Study with flashcards and multiple choice questions; each question includes hints and explanations. Gear up to ace your test!

Acetyl-CoA carboxylase catalyzes the addition of a carboxyl group to acetyl-CoA to form malonyl-CoA, using bicarbonate and biotin as a cofactor. This carboxylation is the first and rate-limiting step of fatty acid synthesis in the cytosol, and the malonyl-CoA formed provides the two-carbon donor units for the fatty acid synthase cycle to build long-chain fatty acids like palmitate. Regulation of ACC ties lipid synthesis to energy and nutritional status: it is activated by citrate (signaling abundant carbohydrate), and inhibited by phosphorylation through energy-sensing pathways like AMPK; malonyl-CoA also inhibits fatty acid entry into mitochondria by suppressing carnitine palmitoyltransferase I, coordinating synthesis with reduced oxidation. The other options refer to different enzymes—malonyl-CoA decarboxylase removes the carboxyl group, citrate synthase makes citrate from acetyl-CoA and oxaloacetate, and complete oxidation of acetyl-CoA occurs in the TCA cycle.