This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of protein and amino acid, Subject name: Biochemistry
[{'content': 'Nicotinamide is derived from \nSelect and explain. \nA. Histidine, B. Methionine, C. Tryptophan, D. Phenylalanine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The enzyme QP Is the rate limiting step in the formation of nicotinamide from Tryptophan.Ref: DM Vasudevan - Textbook of Biochemistry, 7th edition, page no: 240', 'role': 'assistant'}]