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
Rate limiting enzyme in catecholamine biosynthesis is 
Select and explain. 
A. Tyrosine hydroxylase, B. Dopa Decarboxylase, C. Dopamine beta-hydroxylase (DBH), D. Phenylethanolamine-N-Methyltransferase (PNMT)
A: Tyrosine hydroxylase
Answer: A: Tyrosine hydroxylase 
Explanation: Tyrosine Hydroxylase Is Rate-Limiting for Catecholamine BiosynthesisRef: Harper&;s Biochemistry; 30th edition; Chapter 41; The Diversity of the Endocrine System