title: Oxygen metabolism in plant/bacteria interactions: effect of DPI on the pseudo-NAD(P)H oxidase activity of peroxidase.
abstract: Diphenyleneiodonium (DPI) has been used frequently as a specific inhibitor of NADH oxidase activity in studies of plant/pathogen interactions. The present study reports the effect of DPI on the pseudo-oxidative activity of horseradish peroxidase. DPI, like other phenolics, is able to catalytically stimulate NADH oxidation in the presence of exogenous H2O2. The stimulated NADH oxidation has an acidic pH optimum and has an apparent Km of 111 microM NADH. The NADH oxidation rate is linearly proportional to [DPI] and the amount of NADH oxidized is proportional to [H2O2]. Once exogenous H2O2 is depleted, the NADH oxidation is abruptly halted until additional H2O2 is supplied. In some respects DPI appears to mimic the effects of certain anti-oxidants that use HRP to scavenge H2O2 and NAD(P)H as a reductant.
authors.affiliation: Microbiology and Plant Pathology Laboratory, ARS, United States Department of Agriculture, Beltsville, Maryland, 20705, USA. cbaker@asrr.arsusda.gov
authors.forename: C J
authors.initials: CJ
authors.lastname: Baker
authors.forename: K
authors.initials: K
authors.lastname: Deahl
authors.forename: J
authors.initials: J
authors.lastname: Domek
authors.forename: E W
authors.initials: EW
authors.lastname: Orlandi
mesh_terms: D001419:Bacteria / Q000378:metabolism / Q000472:pathogenicity; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006735:Horseradish Peroxidase / Q000037:antagonists & inhibitors; D006861:Hydrogen Peroxide / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors*; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors*; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors*; D009861:Onium Compounds / Q000494:pharmacology*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D010944:Plants / Q000378:metabolism* / Q000382:microbiology*; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D009097:Multienzyme Complexes; D009861:Onium Compounds; D017382:Reactive Oxygen Species; C007517:diphenyleneiodonium; D006861:Hydrogen Peroxide; D006735:Horseradish Peroxidase; C023107:NADH oxidase; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; D010100:Oxygen