title: Detection of singlet (1O2) oxygen phosphorescence during chloroperoxidase-catalyzed decomposition of ethyl hydroperoxide.
abstract: Evidence for the production of singlet molecular oxygen (1O2) during the chloroperoxidase-catalyzed decomposition of ethyl hydroperoxide has been obtained through the use of optical spectroscopy, oxygen electrode experiments, and electron spin resonance (ESR). ESR spin-trapping experiments with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) demonstrate the production of the ethyl peroxyl free radical during the chloroperoxidase/ethyl hydroperoxide reaction. Oxygen and acetaldehyde concentrations suggest that the production of ethyl peroxyl radicals constitutes less than 2% of the decomposition of ethyl hydroperoxide at the concentrations of reactants used. The phosphorescence of 1O2 at 1268 nm was observed during the chloroperoxidase-catalyzed decomposition of ethyl hydroperoxide in deuterium oxide buffer. Chloroperoxidase also catalyzes the decomposition of tert-butyl hydroperoxide to its corresponding peroxyl radical. Alkoxyl and alkyl-DMPO spin adducts were also detected. A much lower yield of 1O2 phosphorescence was observed during the chloroperoxidase-catalyzed decomposition of tert-butyl hydroperoxide. This phosphorescence probably arises through secondary production of alkyl peroxyl radicals. These results suggest that the initial enzyme-dependent production of ethyl peroxyl radicals is followed by enzyme-independent reaction of two peroxyl radicals through the tetroxide intermediate, as originally proposed by Russell (Russell, G. A. (1957) J. Am. Chem. Soc. 79, 3871-3877), to form acetaldehyde, ethyl alcohol, and molecular oxygen.
authors.affiliation: Laboratory of Molecular Biophysics, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709.
authors.forename: R D
authors.initials: RD
authors.lastname: Hall
authors.forename: W
authors.initials: W
authors.lastname: Chamulitrat
authors.forename: N
authors.initials: N
authors.lastname: Takahashi
authors.forename: C F
authors.initials: CF
authors.lastname: Chignell
authors.forename: R P
authors.initials: RP
authors.lastname: Mason
mesh_terms: D002711:Chloride Peroxidase / Q000378:metabolism*; D003497:Cyclic N-Oxides; D004566:Electrodes; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D006863:Hydrogen-Ion Concentration; D008163:Luminescent Measurements; D010100:Oxygen / Q000378:metabolism*; D010544:Peroxidases / Q000378:metabolism*; D010545:Peroxides / Q000378:metabolism*; D026082:Singlet Oxygen; D013053:Spectrophotometry; D013113:Spin Labels; D020122:tert-Butylhydroperoxide
chemical_list: D003497:Cyclic N-Oxides; D005609:Free Radicals; D010545:Peroxides; D013113:Spin Labels; C025577:ethyl hydroperoxide; D026082:Singlet Oxygen; C049375:perhydroxyl radical; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D020122:tert-Butylhydroperoxide; D010544:Peroxidases; D002711:Chloride Peroxidase; D010100:Oxygen