title: Oxidation of 2-nitropropane by horseradish peroxidase. Involvement of hydrogen peroxide and of superoxide in the reaction mechanism.
abstract: Incubation of aqueous solutions of 2-nitropropane in air causes a slow oxidation reaction that generates H(2)O(2). Purified horseradish peroxidase catalyses the oxidation of such preincubated 2-nitropropane solutions according to the equation: [Formula: see text] The pH optimum is 4.5 and K(m) for 2-nitropropane is 16mm. Other nitroalkanes or nitro-aromatics tested are not oxidized at significant rates by peroxidase. H(2)O(2) or 2,4-dichlorophenol increases the rate of 2-nitropropane oxidation by peroxidase. Catalase inhibits the reaction completely. Superoxide dismutase or mannitol, a scavenger of the hydroxyl radical, OH(.), each inhibits partially. Aniline and guaiacol are also powerful inhibitors of 2-nitropropane oxidation. It is suggested that peroxidase uses the traces of H(2)O(2) generated during preincubation of 2-nitropropane to catalyse oxidation of this substrate into a radical species that can reduce O(2) to the superoxide ion, O(2) (-.).O(2) (-.), or OH(.) derived from it, then appears to react with more nitropropane, generating further radicals and H(2)O(2) to continue the oxidation. Inhibition by aniline and guaiacol seems to be due to a competition for H(2)O(2).
mesh_terms: D000473:Alkanes / Q000378:metabolism*; D055598:Chemical Phenomena; D002621:Chemistry; D006735:Horseradish Peroxidase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006861:Hydrogen Peroxide; D007700:Kinetics; D009595:Nitroparaffins / Q000378:metabolism*; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000378:metabolism*; D011407:Propane / Q000031:analogs & derivatives / Q000378:metabolism; D013057:Spectrum Analysis; D013481:Superoxides
chemical_list: D000473:Alkanes; D009595:Nitroparaffins; D013481:Superoxides; D006861:Hydrogen Peroxide; D006735:Horseradish Peroxidase; D010544:Peroxidases; C016617:2-nitropropane; D011407:Propane