This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'Which of the following enzymic activities would you expect to be decreased in thiamine deficiency? \nSelect and explain. \nA. Pyruvate carboxylase, B. Isocitrate dehydrogenase, C. Fumarase, D. a-Ketoglutarate dehydrogenase', 'role': 'user'}, {'content': "Answer: D \nExplanation: In the reaction catalyzed by a-ketoglutarate dehydrogenase complex, thiamine pyrophosphate, the cofactor form of thiamine, functions as a transient carrier of the five-carbon intermediate produced on decarboxylation of a-ketoglutrate. Biotin is a coenzyme of pyruvate carboxylase. Isocitrate dehydrogenase use NAD+ as coenzymes, whereas fumarase has no coenzyme. Ref: Brooks G.F. (2013). Chapter 6. Microbial Metabolism. In G.F. Brooks (Ed),Jawetz, Melnick, & Adelberg's Medical Microbiology, 26e.", 'role': 'assistant'}]