<prompt> Which of the following is the ratelimiting enzyme in the biosynthesis of catecholamines?Dopamine hydroxylaseTyrosinaseDOPA decarboxylaseTyrosine hydroxylase  <response>: 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 