Which of the following is the ratelimiting enzyme in the biosynthesis of catecholamines?: (A) Dopamine hydroxylase, (B) Tyrosinase, (C) DOPA decarboxylase, (D) Tyrosine hydroxylase
Answer is D. Tyrosine hydroxylase is the rate-limiting enzyme in the biosynthesis of catecholamines. Tyrosine is first hydroxylated to form 3,4- dihydroxyphenylalanine (DOPA) by the enzyme tyrosine hydroxylase. This enzyme is abundant in the central nervous system, the sympathetic ganglia, and the adrenal medulla Reference: Harpers illustrated biochemistry 30th edition