All of the following are cofactors used in the reaction catalyzed by pyruvate dehydrogenase EXCEPT .A. NAD+B. Thiamine pyrophosphateC. BiotinD. FAD

C. Biotin

Explanation:

The pyruvate dehydrogenase is one of the three enzymes in the multi-enzyme complex, pyruvate dehydrogenase complex which is responsible for the oxidation of pyruvate from glycolysis to acetylCoA and CO₂. It is known as E₁ in the enzyme complex. The other three enzymes in the complex are dihydrolipoyl transacetylase, E₂, and dihydrilipoyl dehydrogenase, E₃. E₂ is located at the center with E₁ and E₃ located at both ends of E₂. E₁ catalyzes the decarboxylation of pyruvate and the electrons generated are used in the reduction of the disulfide of lipoate bound to E₂ . E₂ catalyses the transfer of acetyl group to coenzyme A, forming acetylCoA. E₃ catalyzes the regeneration of the disulfide form of lipoate and the electrons produced are first passed to FAD and then to NAD+.

Five cofactors are required in the reaction of the pyruvate dehydrogenase complex reaction : thiamine pyrophosphate (TPP), flavine adenine dinucleotide (FAD), coenzyme A (CoA-SH), nicotineamide adenine dinucleotide (NAD), and lipoate.

Biotin is not a cofactor in the reaction catalyzed by pyruvate dehydrogenase.

the answer is symmetrical : )