title: Identification of the 4-amino analogue of tetrahydrobiopterin as a dihydropteridine reductase inhibitor and a potent pteridine antagonist of rat neuronal nitric oxide synthase.
abstract: The binding of tetrahydropteridines with 6-di- and trihydroxypropyl side chains to recombinant rat neuronal nitric oxide (NO) synthase (EC 1.14.13.39) was determined by competition with 6R-[3'-3H]-5,6,7,8-tetrahydro-L-erythro-biopterin (6R-[3'-3H]H4biopterin). Although all but one of the derivatives exhibited only poor affinities (Ki 50 microM), the 4-amino analogue of 6R-H4 biopterin was a potent antagonist of 6R-H4 biopterin binding (Ki 13.2 nM). The 4-amino analogue of 6R-H4 biopterin inhibited NO synthase stimulation by the natural cofactor 6R-H4 biopterin with an IC50 of 1 microM without affecting the basal activity observed in the absence of added 6R-H4 biopterin. Because the 4-amino analogue of 6R-H4biopterin also inhibited dihydropteridine reductase (EC 1.6.99.7; IC50 20 microM), our results support the hypothesis that redox cycling of H4 biopterin might be required for the NO synthase reaction.
authors.affiliation: Institut für Medizinische Chemie und Biochemie, Universität Innsbruck, Austria.
authors.forename: E R
authors.initials: ER
authors.lastname: Werner
authors.forename: E
authors.initials: E
authors.lastname: Pitters
authors.forename: K
authors.initials: K
authors.lastname: Schmidt
authors.forename: H
authors.initials: H
authors.lastname: Wachter
authors.forename: G
authors.initials: G
authors.lastname: Werner-Felmayer
authors.forename: B
authors.initials: B
authors.lastname: Mayer
mesh_terms: D000818:Animals; D001708:Biopterins / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D001921:Brain / Q000166:cytology / Q000201:enzymology; D004093:Dihydropteridine Reductase / Q000037:antagonists & inhibitors*; D007700:Kinetics; D009474:Neurons / Q000201:enzymology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D051381:Rats; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors; D012756:Sheep; D018411:Spodoptera
chemical_list: D011994:Recombinant Proteins; D001708:Biopterins; D019001:Nitric Oxide Synthase; D004093:Dihydropteridine Reductase; C003402:sapropterin