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Biochemistry

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Fatty Acid Oxidation and the Requirement for Carnitine

BIOCHM-CFDFOK

Fatty acids are activated for oxidation in the cytosol by the formation of their respective fatty acyl-CoA ester. The enzyme carnitine palmitoyltransferase 1A (CPT1A) is localized outside of the inner mitochondrial membrane and catalyzes the esterification of fatty acyl-CoA molecules to acyl-carnitine molecules.

Mutations in CPT1A result in inhibition of carnitine palmitoyltransferase 1A activity and consequently, inhibition of long chain fatty acid oxidation. However, oxidation of medium (8-10 Cs) and very long-chain (>22 Cs) fatty acid oxidation is unaffected.

Identify ALL of the following statements which correctly explain why only long chain fatty acid oxidation is affected by a mutation in CPT1A.

Select ALL that apply.

A

Medium chain fatty acids are oxidized in the cytosol and thus, are not dependent upon CPT1A.

B

Very long chain fatty acids are oxidized in the peroxisome and do not require carnitine for entry into the peroxisome.

C

Long chain fatty acyl-CoA molecules require CPT1A to form their respective acyl-carnitine molecules facilitating transfer across the inner mitochondrial membrane.

D

Medium chain fatty acids are able to diffuse across the mitochondrial membranes as fatty acyl-CoA molecules and, therefore, are not dependent upon CPT1A.

E

Only long chain fatty acids are metabolized in the mitochondria and thus dependent upon CPT1A activity for entry into the mitochondria.