Malonyl-CoA

Malonyl-CoA structure

Malonyl-CoA, a coenzyme A derivative of malonic acid, is a pivotal molecule in several cellular biosynthetic processes. It plays central roles in fatty acid biosynthesis, polyketide biosynthesis, and the transportation of alpha-ketoglutarate into the mitochondrial matrix.

Functions

Malonyl-CoA has various functions in cellular processes:

• It acts as a source of 2-carbon units in the elongation of fatty acid chains.
• It facilitates the transport of alpha-ketoglutarate across the mitochondrial membrane into the mitochondrial matrix.
• Commits molecules for fatty acid chain synthesis.

Fatty Acid Biosynthesis

Fatty acid biosynthesis is a process where new fatty acid chains are synthesized, and Malonyl-CoA plays a pivotal role in this pathway:

• Malonyl-CoA originates from the carboxylation of acetyl-CoA, a reaction catalyzed by the enzyme acetyl-CoA carboxylase. During this process, one molecule of acetyl-CoA reacts with bicarbonate, utilizing energy derived from ATP.
• In fatty acid synthesis, the enzyme malonyl coenzyme A:acyl carrier protein transacylase (MCAT) uses Malonyl-CoA. MCAT transfers the malonate from Malonyl-CoA to the terminal thiol of holo-acyl carrier protein (ACP).

Polyketide Biosynthesis

Malonyl-CoA is also fundamental in the biosynthesis of polyketides, primarily in bacterial systems:

MCAT is a crucial enzyme in bacterial polyketide biosynthesis. Along with an acyl carrier protein (ACP) and a polyketide synthase-chain-length factor heterodimer, MCAT constitutes the basic PKS for type II polyketides.

Regulation

Given the importance of Malonyl-CoA in fatty acid synthesis, it is tightly regulated within the cell:

• Malonyl-CoA is a significant inhibitor of the rate-limiting step in beta-oxidation of fatty acids.
• By regulating the enzyme carnitine acyltransferase, Malonyl-CoA prevents fatty acids from associating with carnitine. As a result, fatty acids are barred from entering the mitochondria, the site for fatty acid oxidation and degradation.

See Also

• Fatty acid synthesis
• Polyketides
• Mitochondria
• *Malonyl-CoA decarboxylase
• *Malonyl-CoA decarboxylase deficiency

External links

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