What is the role of malonyl-CoA in fatty acid metabolism?

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Multiple Choice

What is the role of malonyl-CoA in fatty acid metabolism?

Malonyl-CoA sits at the crossroads of fatty acid metabolism. It is produced in the cytosol by acetyl-CoA carboxylase and then serves as the two-carbon donor for fatty acid synthesis, with the growing acyl chain being elongated by sections derived from malonyl-CoA in the fatty acid synthase complex. At the same time, malonyl-CoA acts as a key regulator by inhibiting CPT I, the enzyme that ferries long-chain fatty acyl-CoAs into mitochondria for beta-oxidation. When malonyl-CoA levels are high, transport into the mitochondria is blocked, preventing fatty acid oxidation while synthesis is active. This prevents a futile cycle of simultaneously making and breaking down fatty acids. So, the role of malonyl-CoA is to provide two-carbon units for fatty acid synthesis and to block mitochondrial entry for oxidation when synthesis is underway. It is not an energy source for the electron transport chain, nor the final product of beta-oxidation.

Malonyl-CoA sits at the crossroads of fatty acid metabolism. It is produced in the cytosol by acetyl-CoA carboxylase and then serves as the two-carbon donor for fatty acid synthesis, with the growing acyl chain being elongated by sections derived from malonyl-CoA in the fatty acid synthase complex.

At the same time, malonyl-CoA acts as a key regulator by inhibiting CPT I, the enzyme that ferries long-chain fatty acyl-CoAs into mitochondria for beta-oxidation. When malonyl-CoA levels are high, transport into the mitochondria is blocked, preventing fatty acid oxidation while synthesis is active. This prevents a futile cycle of simultaneously making and breaking down fatty acids.

So, the role of malonyl-CoA is to provide two-carbon units for fatty acid synthesis and to block mitochondrial entry for oxidation when synthesis is underway. It is not an energy source for the electron transport chain, nor the final product of beta-oxidation.

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