This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Inborn Errors of Metabolism, Subject name: Pediatrics
[{'content': 'Hyperphenylalaninemia is due to defect in the enzyme: \nSelect and explain. \nA. Phenylalanine hydroxylase:, B. Tyrosinase, C. Homogentisic acid oxidase, D. Ornithine transcarbamylase', 'role': 'user'}, {'content': "Answer: A \nExplanation: a. Phenylalanine hydroxylase(Ref: Nelson's 20/e p 636-636)Deficiency of the enzyme phenylalanine hydroxylase or of its cofactor tetrahydrobiopterin (BH4) causes accumulation of phenylalanine in body fluids and in the brain.", 'role': 'assistant'}]