title: Peroxyl, alkoxyl, and carbon-centered radical formation from organic hydroperoxides by chloroperoxidase.
abstract: The decomposition of organic hydroperoxides as catalyzed by chloroperoxidase was investigated with electron spin resonance (ESR) spectroscopy. Tertiary peroxyl radicals were directly detected by ESR from incubations of tert-butyl hydroperoxide or cumene hydroperoxide with chloroperoxidase at pH 6.4. Peroxyl, alkoxyl, and carbon-centered free radicals from tertiary hydroperoxide/chloroperoxidase systems were successfully trapped by the spin trap 5,5-dimethyl-1-pyrroline N-oxide, whereas alkoxyl radicals were not detected in the ethyl hydroperoxide/chloroperoxidase system. The carbon-centered free radicals were further characterized by spin-trapping studies with tert-nitrosobutane. Oxygen evolution measured by a Clark oxygen electrode was detected for all the hydroperoxide/chloroperoxidase systems. The classical peroxidase mechanism is proposed to describe the formation of peroxyl radicals. In the case of tertiary peroxyl radicals, their subsequent self-reactions result in the formation of alkoxyl free radicals and molecular oxygen. beta-Scission and internal hydrogen atom transfer reactions of the alkoxyl free radicals lead to the formation of various carbon-centered free radicals. In the case of the primary ethyl peroxyl radicals, decay through the Russell pathway forms molecular oxygen.
authors.affiliation: Laboratory of Molecular Biophysics, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709.
authors.forename: W
authors.initials: W
authors.lastname: Chamulitrat
authors.forename: N
authors.initials: N
authors.lastname: Takahashi
authors.forename: R P
authors.initials: RP
authors.lastname: Mason
mesh_terms: D001555:Benzene Derivatives / Q000378:metabolism; D055598:Chemical Phenomena; D002621:Chemistry; D002711:Chloride Peroxidase / Q000378:metabolism*; D003497:Cyclic N-Oxides; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D006861:Hydrogen Peroxide / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D009603:Nitroso Compounds; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D010544:Peroxidases / Q000378:metabolism*; D010545:Peroxides / Q000378:metabolism; D013113:Spin Labels; D020122:tert-Butylhydroperoxide
chemical_list: D001555:Benzene Derivatives; D003497:Cyclic N-Oxides; D005609:Free Radicals; D009603:Nitroso Compounds; D010545:Peroxides; D013113:Spin Labels; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D020122:tert-Butylhydroperoxide; D006861:Hydrogen Peroxide; D010544:Peroxidases; D002711:Chloride Peroxidase; C034526:tert-nitrosobutane; C007164:cumene hydroperoxide; D010100:Oxygen