malonülaCoA

Malonyl-CoA is the Coenzyme A thioester of malonic acid and a central intermediate in lipid metabolism. The standard term is malonyl-CoA, though some nonstandard spellings such as malonülaCoA appear in informal sources. It is produced by acetyl-CoA carboxylase (ACC) through the ATP- and biotin-dependent carboxylation of acetyl-CoA, incorporating a carbon dioxide molecule to yield malonyl-CoA. This reaction links carbohydrate metabolism to fatty acid synthesis.

In fatty acid biosynthesis, malonyl-CoA serves as the two-carbon donor that extends growing acyl chains. In many organisms, malonyl-CoA is consumed by fatty acid synthase to build long-chain fatty acids like palmitate. In bacteria, plants, and fungi, malonyl-CoA can also feed into polyketide biosynthesis, where it acts as an extender unit in the production of diverse secondary metabolites. Beyond its role as a substrate, malonyl-CoA participates in regulatory processes that coordinate lipid synthesis with energy status.

Regulation of malonyl-CoA levels is a key control point in metabolism. Acetyl-CoA carboxylase activity is stimulated by citrate and inhibited by AMP-activated protein kinase (AMPK)–mediated phosphorylation, aligning fatty acid synthesis with cellular energy. Malonyl-CoA also inhibits carnitine palmitoyltransferase 1 (CPT1), reducing mitochondrial fatty acid entry for β-oxidation when synthesis is favored. Malonyl-CoA decarboxylase degrades malonyl-CoA to acetyl-CoA and CO2, providing a mechanism to relieve inhibition of fatty acid oxidation when needed.

Overall, malonyl-CoA is a pivotal metabolite that connects carbohydrate and lipid metabolism, regulating both the synthesis and oxidation of fatty acids across diverse organisms.