Monoamine Methyltransferases: Phenylethanolamine N-Methyltransferase and Catechol O-Methyltransferase

Phenylethanolamine N -methyltransferase (PNMT) (EC 2.1.1.28, S -adenosyl-L -methionine: phenylethanolamine N -methyltransferase) is the enzyme that catalyzes the biosynthesis of norepinephrine [noradrenaline; (NA)] to epinephrine [adrenaline; (A)] in the presence of S -adenosyl-L -methionine (SAM) as the methyl donor. The enzyme is localized mainly in the adrenal medulla and in small amounts in discrete brain regions containing A cell bodies and nerve terminals. Adrenal PNMT has been extensively purified and well characterized, but the brain enzyme has not been well studied, although many similarities between them have been observed.