Regulation of phenylethanolamine N-methyl transferase

Phenylethanolamine N-methyl transferase (PNMT) catalyzes the methylation of norepinephrine, forming epinephrine in the adrenal medulla. In vitro, PNMT accepts a variety of phenylethanolamines and phenylethylenediamines as substrates. It is inhibited by phenethylamines and other compounds structurally similar to its substrates, as well as by agents that bind to sulfhydryl groups. Specific inhibitors of PNMT may be useful pharmacologic tools and potentially drugs. A group of benzylamines, including 2,3-dichloro-α-methylbenzylamine, are among the most potent inhibitors presently known. In vivo, maintenance of PNMT levels in the adrenal medulla is dependent upon an adequate supply of glucocorticoids from the adrenal cortex. Neural input to the medulla may also influence the enzyme level. The possibility that product inhibition may influence PNMT activity in vivo requires further study.