ChEBI: Alpha-methyl-L-tyrosine is an L-tyrosine derivative that consists of L-tyrosine bearing an additional methyl substituent at position 2. An inhibitor of the enzyme tyrosine 3-monooxygenase, and consequently of the synthesis of catecholamines. It is used to control the symptoms of excessive sympathetic stimulation in patients with pheochromocytoma. It has a role as an antihypertensive agent and an EC 1.14.16.2 (tyrosine 3-monooxygenase) inhibitor. It is a L-tyrosine derivative and a non-proteinogenic L-alpha-amino acid.NCI Thesaurus (NCIt): Metyrosine is a methylated tyrosine, a catecholamine synthesis antagonist with antihypertensive property. Metyrosine competitively inhibits tyrosine 3-monooxygenase, an enzyme that activates molecular oxygen to catalyze the hydroxylation of tyrosine to dihydroxyphenylalanine (Dopa), an intermediate to catecholamine (dopamine, norepinephrine, and epinephrine) production. This agent reduces the elevated levels of catecholamines associated with pheochromocytoma, thereby preventing hypertension.