Which vitamin is a cofactor for the pyruvate dehydrogenase complex?

Which vitamin is a cofactor for the pyruvate dehydrogenase complex?

• A. Riboflavin
• B. Niacin
• C. Pantothenic acid
• D. Thiamine (Vitamin B1)

Answer: (D)

The key idea is how the pyruvate dehydrogenase complex starts the process that turns pyruvate into acetyl-CoA, which needs specific vitamins to function. For the first step, the E1 enzyme uses thiamine in the form of thiamine pyrophosphate to help decarboxylate pyruvate. This cofactor stabilizes the reaction’s carbanion intermediate and enables transfer of the resulting two-carbon unit to the next part of the complex. That direct, essential role in initiating the reaction is why this vitamin is the correct choice. The other vitamins listed support other parts of the overall process—riboflavin provides FAD, niacin provides NAD+, and pantothenic acid provides CoA—but the initiating cofactor for the PDH complex is thiamine.

The key idea is how the pyruvate dehydrogenase complex starts the process that turns pyruvate into acetyl-CoA, which needs specific vitamins to function. For the first step, the E1 enzyme uses thiamine in the form of thiamine pyrophosphate to help decarboxylate pyruvate. This cofactor stabilizes the reaction’s carbanion intermediate and enables transfer of the resulting two-carbon unit to the next part of the complex. That direct, essential role in initiating the reaction is why this vitamin is the correct choice. The other vitamins listed support other parts of the overall process—riboflavin provides FAD, niacin provides NAD+, and pantothenic acid provides CoA—but the initiating cofactor for the PDH complex is thiamine.