Which deficiency is associated with impaired beta-oxidation of long-chain fatty acids?

Which deficiency is associated with impaired beta-oxidation of long-chain fatty acids?

• A. Long-chain acyl-CoA dehydrogenase deficiency
• B. MCAD deficiency
• C. CPT II deficiency
• D. Carnitine deficiency

Answer: (A)

Long-chain fatty acids rely on a specific enzyme in the beta-oxidation pathway to begin oxidation in the mitochondria. The enzyme that handles long-chain substrates is long-chain acyl-CoA dehydrogenase; when this deficiency occurs, beta-oxidation of long-chain fatty acids is directly impaired, leading to an inability to generate sufficient acetyl-CoA and energy from those fats, especially during fasting or stress. The other conditions affect different parts of the process or different chain lengths: medium-chain acyl-CoA dehydrogenase deficiency disrupts oxidation of medium-chain fatty acids; CPT II deficiency affects the transport of long-chain fatty acids into the mitochondria for oxidation (not the initial dehydrogenation step); and carnitine deficiency impairs transport of long-chain fatty acids into mitochondria more broadly. Therefore, the long-chain acyl-CoA dehydrogenase deficiency best explains impaired beta-oxidation of long-chain fatty acids.

Long-chain fatty acids rely on a specific enzyme in the beta-oxidation pathway to begin oxidation in the mitochondria. The enzyme that handles long-chain substrates is long-chain acyl-CoA dehydrogenase; when this deficiency occurs, beta-oxidation of long-chain fatty acids is directly impaired, leading to an inability to generate sufficient acetyl-CoA and energy from those fats, especially during fasting or stress. The other conditions affect different parts of the process or different chain lengths: medium-chain acyl-CoA dehydrogenase deficiency disrupts oxidation of medium-chain fatty acids; CPT II deficiency affects the transport of long-chain fatty acids into the mitochondria for oxidation (not the initial dehydrogenation step); and carnitine deficiency impairs transport of long-chain fatty acids into mitochondria more broadly. Therefore, the long-chain acyl-CoA dehydrogenase deficiency best explains impaired beta-oxidation of long-chain fatty acids.