title: Reaction of 1-amino- and 1-chlorophthalazine with mammalian molybdenum hydroxylases in vitro.
abstract: 1-Amino- and 1-chlorophthalazine were tested for possible substrate activity with partially purified rabbit-liver aldehyde oxidase and bovine-milk xanthine oxidase. 1-Chlorophthalazine was a more efficient substrate than the parent compound, phthalazine, with either aldehyde oxidase or xanthine oxidase. The oxidation product of 1-chlorophthalazine was identified as 4-chloro-1-(2H)-phthalazinone on the basis of chromatographic, infra-red and mass-spectral data. 1-Aminophthalazine was oxidized by aldehyde oxidase to 4-amino-1-(2H)-phthalazinone but was a competitive inhibitor of xanthine oxidase. Kinetic studies at different pH values indicated that, in each case, it is the unprotonated form of 1-aminophthalazine that reacts with the molybdenum hydroxylases.
mesh_terms: D042931:Aldehyde Oxidase; D000445:Aldehyde Oxidoreductases / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D002855:Chromatography, Thin Layer; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008892:Milk / Q000201:enzymology; D008982:Molybdenum; D010084:Oxidation-Reduction; D010793:Phthalazines / Q000378:metabolism*; D011724:Pyridazines / Q000378:metabolism*; D011817:Rabbits; D013329:Structure-Activity Relationship; D014969:Xanthine Oxidase / Q000378:metabolism*
chemical_list: D010793:Phthalazines; D011724:Pyridazines; D008982:Molybdenum; D014969:Xanthine Oxidase; D000445:Aldehyde Oxidoreductases; D042931:Aldehyde Oxidase