Figure 2

Mammalian catecholamine biosynthetic pathway from Phenylalanine. Phenylalanine hydroxylase converts phenylalanine to tyrosine. Tyrosine hydroxylase hydroxylates tyrosine to L-DOPA. L-DOPA is converted to dopamine by aromatic amino acid decarboxylase. Dopamine-β-hydroxylase hydroxylates dopamine to norepinephrine, which is then methylated to epinephrine by phenylethanolamine N-methyltransferase.