Reversal of the superoxide dismutase reaction revisited.
Reversal of the superoxide dismutase (SOD) reaction was measured in terms of the reduction of tetranitromethane (TNM) by O2-. Cu,ZnSOD caused a biphasic reduction of TNM by H2O2. The rapid initial phase was stoichiometric with the enzyme and was followed by a slower catalytic phase that was oxygen dependent and was augmented by HCO3-. The reaction scheme explaining this behavior is presented and a rate constant for the reduction of O2 by the cuprous enzyme is estimated. This rate constant is so low that it precludes significant O2- production by the reduced enzyme under the conditions explored.
Liochev
Stefan I
SI
Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.
Fridovich
Irwin
I
D000838:Anions; D001639:Bicarbonates / Q000737:chemistry; D002254:Carbonates / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D005609:Free Radicals; D006861:Hydrogen Peroxide / Q000737:chemistry; D007477:Ions / Q000737:chemistry; D008956:Models, Chemical; D016877:Oxidants / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism*; D013774:Tetranitromethane / Q000737:chemistry
D000838:Anions; D001639:Bicarbonates; D002254:Carbonates; D005609:Free Radicals; D007477:Ions; D016877:Oxidants; D006861:Hydrogen Peroxide; D013482:Superoxide Dismutase; D013774:Tetranitromethane; D010100:Oxygen