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': 'Xanthurenic acid is produced in \nSelect and explain. \nA. Tyrosine metabolism, B. Tryptophan metabolism, C. Cysteine metabolism, D. Valine metabolism', 'role': 'user'}, {'content': 'Answer: B \nExplanation: In the metabolism of Tryptophan, Kynurenin is an intermediate step. The accumulated Kynurenine is shunted to Xanthurenic acid. So, in pyridoxal deficiency, Xanthurenic acid is excreted in the urine.Ref: DM Vasudevan - Textbook of Biochemistry, 7th edition, page no: 240', 'role': 'assistant'}]