title: Characterization of glycine N-methyltransferase from rabbit liver.
abstract: The enzymatic properties of glycine N-methyltransferase from rabbit liver and the effects of endogenous adenosine nucleosides, nucleotides and methyltransferase inhibitors were investigated using a photometrical assay to detect sarcosine with o-dianisidine as a dye. After isolation and purification the denatured enzyme showed a two-banded pattern by SDS-PAGE. The enzyme was highly specific for its substrates with a pH-optimum at pH 8.6. Glycine N-methyltransferase exhibits Michaelis-Menten kinetics for its substrates, S-adenosylmethionine and glycine, respectively. The apparent Km and Vmax values were determined for both the substrates, the other substrate being present at saturating concentrations. The enzyme was strongly inhibited in the presence of S-adenosylhomocysteine, 3-deazaadenosine, and 5'-S-isobutylthio-5'-deoxyadenosine. All other inhibitors investigated, adenosine, 2'-deoxyadenosine, aciclovir, and 5'-N-ethylcarboxamidoadenosine were poor inhibitors of the methylation reaction. Adenine nucleotides and vidarabin were without effect on the enzymatic activity. Based on the kinetic data glycine N-methyltransferase from rabbit liver exhibits appreciable activity at physiological S-adenosylmethionine and S-adenosylhomocysteine levels.
authors.affiliation: Department of Pharmacology and Toxicology, Wilhelmstrasse 56, Faculty of Medicine, Univesrity of Tübingen, D-72074 Tübingen, Germany. doris.kloor@uni-tuebingen.de
authors.forename: Doris
authors.initials: D
authors.lastname: Kloor
authors.forename: Katrin
authors.initials: K
authors.lastname: Karnahl
authors.forename: Jost
authors.initials: J
authors.lastname: Kömpf
mesh_terms: D000818:Animals; D004791:Enzyme Inhibitors / Q000737:chemistry; D050938:Glycine N-Methyltransferase; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008780:Methyltransferases / Q000737:chemistry* / Q000302:isolation & purification; D011489:Protein Denaturation; D011817:Rabbits; D013379:Substrate Specificity
chemical_list: D004791:Enzyme Inhibitors; D008780:Methyltransferases; D050938:Glycine N-Methyltransferase