Enzymatic 0-Methylation of Epinephrine and Other Catechols*

Many studies in vitro have implicated cytochrome oxidase and monoamine oxidase in the metabolism of epinephrine and other cateehol amines (2). However, no evidence for the participation of cytochrome oxidase in the metabolism of epinephrine in viva has been obtained. Furthermore, several investigations have indicated that monoamine oxidase plays only a minor role in the inactivation of epinephrine (3-5). Recently, Armstrong and McMillan have shown that a major metabolic product of norepinephrine in man is 3-methoxy-4-hydroxymandelic acid (6). Work in this laboratory has also demonstrated that O-methylation of epinephrine and other catechols precedes deamination in viva (7, 8). These observations suggested the presence of an enzyme that can carry out the 0-methylation of catechol amines. This paper describes the properties of an enzyme that transfers the methyl group of S-adenosylmethionine to the hydroxyl group in position 3 of epinephrine and other catechols.