title: Biological defense mechanisms. Evidence for the participation of superoxide in bacterial killing by xanthine oxidase.
abstract: Incubation of either Staphylococcus epidermidis or Escherichia coli with a sufficiently high concentration of xanthine oxidase, an enzyme capable of reducing oxygen to superoxide (O2-), resulted in the death of the microorganisms. Protection against the killing os S. epidermidis by xanthine oxidase was afforded by superoxide dismutase, an enzyme which converts O2- to O2 and H2O2, and also by catalase, which destroys H2O2. These findings indicate that neither O2- nor H2O2 were able to kill S. epidermidis under the experimental conditions, but that the bactericidal agent was the product of a reaction between O2- and H2O2. By contrast, E. coli was protected by catalase but not by superoxide dismutase. With this organism, therefore, H2O2 appears to have been the bactericidal agent.
mesh_terms: D000838:Anions / Q000494:pharmacology; D001770:Blood Bactericidal Activity; D002374:Catalase / Q000494:pharmacology; D003864:Depression, Chemical; D004926:Escherichia coli / Q000187:drug effects*; D006861:Hydrogen Peroxide / Q000378:metabolism / Q000494:pharmacology; D008353:Mannitol / Q000494:pharmacology; D010100:Oxygen / Q000494:pharmacology*; D013210:Staphylococcus / Q000187:drug effects*; D013482:Superoxide Dismutase / Q000378:metabolism / Q000494:pharmacology; D014969:Xanthine Oxidase / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D000838:Anions; D008353:Mannitol; D006861:Hydrogen Peroxide; D002374:Catalase; D013482:Superoxide Dismutase; D014969:Xanthine Oxidase; D010100:Oxygen