Light-stimulated formation of hydrogen peroxide and hydroxyl radical in the presence of uroporphyrin and ascorbate.
Blue light irradiation of 2-deoxyribose (DOR) in the presence of uroporphyrin I (UP), ascorbate (AH-), trace iron, and phosphate buffer resulted in a strong stimulation of hydroxyl radical (OH.)-dependent oxidation of DOR. Photostimulated generation of H2O2 was monitored after removal of residual AH- (i) by ascorbate oxidase treatment, or (ii) by anion exchange on mini-columns of DEAE-Sephadex. Irradiation of the above mixture produced a strong burst of H2O2 which was intensified by desferrioxamine and suppressed by catalase or EDTA. The mechanism suggested by these observations is one in which photoreduction of UP to the radical anion initiates the formation of H2O2, which gives rise to OH. via Fenton chemistry. This is the first known investigation of H2O2 fluxes in a Type I (free radical) photoreaction involving AH- as the electron donor.
Bachowski
G J
GJ
Department of Biochemistry, Medical College of Wisconsin, Milwaukee 53226.
Girotti
A W
AW
D001204:Ascorbate Oxidase / Q000378:metabolism; D001205:Ascorbic Acid / Q000528:radiation effects*; D002852:Chromatography, Ion Exchange; D005609:Free Radicals; D006861:Hydrogen Peroxide; D006878:Hydroxides; D017665:Hydroxyl Radical; D007700:Kinetics; D008027:Light; D011166:Porphyrins / Q000528:radiation effects*; D014578:Uroporphyrins / Q000528:radiation effects*
D005609:Free Radicals; D006878:Hydroxides; D011166:Porphyrins; D014578:Uroporphyrins; D017665:Hydroxyl Radical; D006861:Hydrogen Peroxide; D001204:Ascorbate Oxidase; D001205:Ascorbic Acid