This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: vitamins, Subject name: Biochemistry
[{'content': 'Tryptophan is required for synthesis of which vitamin? \nSelect and explain. \nA. Folic acid, B. Thiamine, C. Niacin, D. Riboflavin', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Tryptophan is required for the synthesis of Niacin. In the major pathway, kynureninase is an enzyme dependent on pyridoxal phosphate (enzyme 2, Fig.17.8). Therefore, in vitamin B6 deficiency, the pathway is blocked at this level. This leads to niacin deficiency and manifestations of pellagra. 7. Quinolinate phosphoribosyl transferase is the rate-limiting enzyme in the conversion of niacin to NAD+. About 60 mg of tryptophan is equivalent to 1 mg of niacin. Reference: Vasudevan Textbook of Biochemistry pg no. 211, 395', 'role': 'assistant'}]