This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Biochemistry
[{'content': 'Rate limiting enzyme in catecholamine biosynthesis is \nSelect and explain. \nA. Tyrosine hydroxylase, B. Dopa Decarboxylase, C. Dopamine beta-hydroxylase (DBH), D. Phenylethanolamine-N-Methyltransferase (PNMT)', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Tyrosine Hydroxylase Is Rate-Limiting for Catecholamine BiosynthesisRef: Harper&;s Biochemistry; 30th edition; Chapter 41; The Diversity of the Endocrine System', 'role': 'assistant'}]