Enzymatic O-methylation of norepinephrine: Studies on the site of methylation by high pressure liquid chromatography

Abstract

Catechol O-methyltransferase (COMT, EC 2.1.1.6) catalyzes transfer of a methyl group from S-adenosylmethionine (SAM) to a phenolic group of catechol substrates to yield mono-methylated catechols and S-adenosylhomocysteine (SAH). The site of O-methylation of catechol deriavatives has been the subject of considerable investigation in the past (Creveling et al., 1972; Creveling et al., 1981; Firnau et al., 1980). In mostinstances the meta- and para-methylated products of 4-substituted catechols, formed by COMT, have been analyzed by thin layer chromatography. For several catecholamines including norepinephrine the methylated products can only be separated and quantitated after appropriate derivatives have been prepared. In this paper we describe a high pressure liquid chromatographic (HPLC) system for the separation of methylated products of norepinephrine. The HPLC system was used to study the effect of pH on relative meta-and para-methylation of norepinephrine.