title: Properties of catechol O-methyltransferases from brain and liver of rat and human.
abstract: Kinetic and electrophoretic properties of catechol O-methyltransferases (EC 2.1.1.6) from brain and liver were studied. The enzyme of either rat or human tissues exhibited a single molecular form when subjected to electrophoresis at pH7.9. At pH9 a second, apparently oxidized, form was detected. Isoelectric-focusing experiments also indicated only one enzyme form, which was identical from extracts of brain and liver of each species (pI = 5.2 for rat, 5.5 for human). Similarities between brain and liver catechol O-methyltransferase of a given species were also demonstrated by kinetic parameters, meta/para ratios of products, and inhibitor potencies. Human catechol O-methyltransferase exhibited lower Km values than did the rat enzyme for S-adenosyl-L-methionine, dopamine and dihydroxybenzoic acid. Adrenochrome inhibited both rat and human enzyme. It was concluded (1) that only a single enzyme form could be demonstrated in the physiological pH region; (2) that catechol O-methyltransferase of brain could not be distinguished from the liver enzyme of the same species; and (3) that species differences exist between the enzymes of rat and human tissues.
mesh_terms: D000323:Adrenochrome / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000201:enzymology*; D002394:Catechol O-Methyltransferase; D065098:Catechol O-Methyltransferase Inhibitors; D004298:Dopamine; D004586:Electrophoresis; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D062385:Hydroxybenzoates; D007223:Infant; D007525:Isoelectric Focusing; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008297:Male; D008875:Middle Aged; D008968:Molecular Conformation; D008970:Molecular Weight; D010084:Oxidation-Reduction; D051381:Rats; D012436:S-Adenosylmethionine
chemical_list: D065098:Catechol O-Methyltransferase Inhibitors; D062385:Hydroxybenzoates; D000323:Adrenochrome; D012436:S-Adenosylmethionine; D002394:Catechol O-Methyltransferase; D004298:Dopamine