Catechol-O-Methyltransferase des Menschen
Catechol-O-methyltransferase in Man
A S-adenosylmethionin: catechol-O-methyltransferase, which catalyses the methylation of catecholamines and of 2-hydroxyoestrogens, is localised in the 150000 × g supernatant of human placenta. The enzyme was purified 66fold by ammonium sulphate precipitation and by repeated filtration of the ammonium sulphate precipitate through a Sephadex G-100 column. In the pH range of 6–8, the activity of the enzyme increased steadily. The Michaelis-Menten constants were found to be 43.5 × 10−5 M for adrenaline and 7.8 × 10−5 M for S-adenosylmethionine. The enzyme shows a temperature optimum at 50° the activation energy of the reaction was 17.3 kcal/mole within the range of 24–42°. The methylation of adrenaline is inhibited by 2-hydroxyoestradiol-17β The inhibitor constant was found to be 17.4 × 10−6 M.