Nitroxyl (NO-): a substrate for superoxide dismutase.
The interactions of Cu, Zn superoxide dismutase (SOD) with nitroxyl (NO-) and nitric oxide (NO), both of which are thought to be biologically significant, have been studied but remain undefined. Having previously noted that NO- can reduce Cu (II), Zn SOD aerobically, we now report that it also can do so anaerobically and that Cu, Zn SOD can catalyze the elimination of NO(-) in the absence of O2.NO- acts as a reductant of ferricytochrome c anaerobically, but in the presence of O2 causes the oxidation of ferrocytochrome c and NADPH. Equivalent fluxes of NO-, and NO + O2- were able to comparably oxidize NADPH, but the oxidation by NO + O2- was more than fivefold more sensitive to inhibition by Cu, Zn SOD than was the oxidation by NO-. Thus Cu, Zn SOD inhibited NADPH oxidation by NO- by a route independent of catalyzing the dismutation of O2. Plausible mechanisms for those observations are offered and rate constants are estimated.
Liochev
Stefan I
SI
Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.
Fridovich
Irwin
I
D000332:Aerobiosis; D000693:Anaerobiosis; D000838:Anions; D002384:Catalysis; D003574:Cytochrome c Group / Q000737:chemistry; D009249:NADP / Q000737:chemistry; D009589:Nitrogen Oxides / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D013482:Superoxide Dismutase / Q000737:chemistry*
D000838:Anions; D003574:Cytochrome c Group; D009589:Nitrogen Oxides; D009249:NADP; D013482:Superoxide Dismutase; C039900:nitroxyl; D010100:Oxygen