Which of the following reactions is catalyzed by carnitine acyltransferase?

• A. Conversion of pyruvate to acetyl-CoA
• B. Transfer of an acyl group from acyl-CoA to carnitine, forming acyl-carnitine and CoA
• C. Phosphorylation of glucose to glucose-6-phosphate
• D. Hydrolysis of ATP to ADP and inorganic phosphate

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the role of carnitine acyltransferase. This enzyme is involved in fatty acid metabolism, specifically in the transport of fatty acids into the mitochondria for β-oxidation. It facilitates the transfer of acyl groups from acyl-CoA to carnitine, forming acyl-carnitine and CoA.
2. Step 2: Analyze the given options. The first option, 'Conversion of pyruvate to acetyl-CoA,' is catalyzed by pyruvate dehydrogenase, not carnitine acyltransferase. The second option, 'Transfer of an acyl group from acyl-CoA to carnitine, forming acyl-carnitine and CoA,' matches the function of carnitine acyltransferase. The third option, 'Phosphorylation of glucose to glucose-6-phosphate,' is catalyzed by hexokinase or glucokinase. The fourth option, 'Hydrolysis of ATP to ADP and inorganic phosphate,' is a general reaction catalyzed by ATPases.
3. Step 3: Focus on the correct reaction. Carnitine acyltransferase specifically catalyzes the transfer of an acyl group from acyl-CoA to carnitine, forming acyl-carnitine and CoA. This reaction is crucial for the transport of long-chain fatty acids into the mitochondria.
4. Step 4: Relate the reaction to its biological significance. The formation of acyl-carnitine allows fatty acids to cross the inner mitochondrial membrane, where they can undergo β-oxidation to produce energy in the form of ATP.
5. Step 5: Summarize the key concept. Carnitine acyltransferase is essential for fatty acid metabolism, and its specific role is the transfer of acyl groups from acyl-CoA to carnitine, enabling the transport of fatty acids into the mitochondria for energy production.