High Quality Content by WIKIPEDIA articles! Alpha-methyl-p-tyrosine (AMPT) is a tyrosine hydroxylase enzyme inhibitor. Alpha-methyl-p-tyrosine (AMPT) is a non-endogenous drug involved in the catecholamine biosynthetic pathway. AMPT inhibits tyrosine hydroxylase whose enzymatic activity is regulated through the phosphorylation of different serine residue regulatory domain sites. Catecholamine biosynthesis starts with dietary tyrosine, which is hydroxylated by the enzyme tyrosine hydroxylase. It is hypothesized that AMPT competes with tyrosine at the tyrosine-binding site, causing inhibition of tyrosine hydroxylase.