title: Effect of superoxide dismutase on the autoxidation of various hydroquinones--a possible role of superoxide dismutase as a superoxide:semiquinone oxidoreductase.
abstract: The autoxidation of DT-diaphorase-reduced 1,4-naphthoquinone, 2-OH-1,4-naphthoquinone, and 2-OH-p-benzoquinone is efficiently prevented by superoxide dismutase. This effect was assessed in terms of an inhibition of NADPH oxidation (over the amount required to reduce the available quinone), O2 consumption, and H2O2 formation. Superoxide dismutase also affects the distribution of molecular products -hydroquinone/quinone-involved in autoxidation, by favoring the accumulation of the reduced form of the above quinones. In contrast, the rate of autoxidation of DT-diaphorase-reduced 1,2-naphthoquinone is enhanced by superoxide dismutase, as shown by increased rates of NADPH oxidation, O2 consumption, and H2O2 formation and by an enhanced accumulation of the oxidized product, 1,2-naphthoquinone. These findings suggest that superoxide dismutase can either prevent or enhance hydroquinone autoxidation. The former process would imply a possible new activity displayed by superoxide dismutase involving the reduction of a semiquinone by O2-.. This activity is probably restricted to the redox properties of the semiquinones under study, as indicated by the failure of superoxide dismutase to prevent autoxidation of 1,2-naphthohydroquinone.
authors.affiliation: Department of Pathology II, University of Linköping, Sweden.
authors.forename: E
authors.initials: E
authors.lastname: Cadenas
authors.forename: D
authors.initials: D
authors.lastname: Mira
authors.forename: A
authors.initials: A
authors.lastname: Brunmark
authors.forename: C
authors.initials: C
authors.lastname: Lind
authors.forename: J
authors.initials: J
authors.lastname: Segura-Aguilar
authors.forename: L
authors.initials: L
authors.lastname: Ernster
mesh_terms: D006873:Hydroquinones; D007700:Kinetics; D016660:NAD(P)H Dehydrogenase (Quinone); D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D011808:Quinone Reductases / Q000378:metabolism; D013053:Spectrophotometry; D013482:Superoxide Dismutase / Q000378:metabolism*; D013481:Superoxides
chemical_list: D006873:Hydroquinones; D013481:Superoxides; D013482:Superoxide Dismutase; D016660:NAD(P)H Dehydrogenase (Quinone); D011808:Quinone Reductases