This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous system, Subject name: Physiology
[{'content': 'The rate-limiting step in the biosynthesis of catecholamines is catalyzed by \nSelect and explain. \nA. Tyrosine hydroxylase, B. Dopa decarboxylase, C. Dopa mine f3 hydroxylase, D. Catechol-O-methyltransferase', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The rate limiting step in the synthesis of catecholamines is catalysed by tyrosine hydroxylase Ref : guyton and hall textbook of medical physiology 12 edition page number:605,606,607', 'role': 'assistant'}]