ACACA (acetyl-CoA carboxylase alpha) is a cytosolic enzyme that catalyzes the carboxylation of acetyl-CoA to malonyl-CoA, representing the first and rate-limiting step of de novo fatty acid biosynthesis 123. This two-step reaction involves ATP-dependent carboxylation of biotin carried by the biotin carboxyl carrier domain, followed by carboxyl group transfer from carboxylated biotin to acetyl-CoA 123. ACACA activity is regulated by AMPK-mediated phosphorylation, which inhibits the enzyme and suppresses lipogenesis 4. The enzyme plays critical roles in metabolic regulation, as demonstrated by its involvement in mTOR malonylation—elevated malonyl-CoA levels cause post-translational malonylation of mTOR at lysine 1218, impairing mTORC1 kinase activity and reducing angiogenesis 5. ACACA is clinically significant in cancer and metabolic diseases. Mice with mutations preventing AMPK phosphorylation of ACC1 develop increased hepatic lipogenesis and liver lesions, while ACC inhibitors like ND-654 suppress hepatocellular carcinoma development and improve survival when used alone or with sorafenib 4. The enzyme is also implicated in osteoarthritis pathogenesis, where NFIA-regulated ACACA expression contributes to altered fatty acid metabolism in articular chondrocytes 6.