Thiamine is essential for: (A) Isocitrate dehydrogenase, (B) Succinate dehydrogenase, (C) Pyruvate dehydrogenase, (D) Acetyl CoA synthetase
Answer is C. The  enzyme  pyruvate  dehydrogenase catalyses  (oxidative  decarboxylation)  the irreversible conversion of  pyruvate to  acetyl CoA. This reaction is dependent on thiamine pyrophosphate.