Oxidation of 3-hydroxykynurenine catalyzed by methemoglobin with hydrogen peroxide.
Methemoglobin (metHb) with H2O2 catalyzed the oxidation of 3-hydroxykynurenine (3-HKY) in the reaction mixture of metHb, 3-HKY, and H2O2. The spectrophotometric experiments suggest the following mechanism for the 3-HKY oxidation by metHb with H2O2. MetHb first reacts with H2O2 to form the ferryl complex of Hb. This species then oxidizes 3-HKY, while it returns to metHb. 3-HKY was more reactive with the ferryl complex than glutathione but less reactive than ascorbic acid. Scavengers of the hydroxyl radical, dimethyl sulfoxide and ethanol, scarcely inhibited the 3-HKY oxidation by metHb with H2O2. Desferrioxamine, a metal chelator, hardly suppressed the 3-HKY oxidation. These results indicate that the hydroxyl radical is not involved in the 3-HKY oxidation by metHb with H2O2.
Ishii
T
T
Department of Biochemistry, Wakayama Medical College, Japan.
Iwahashi
H
H
Sugata
R
R
Kido
R
R
D005609:Free Radicals; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D006878:Hydroxides / Q000378:metabolism; D017665:Hydroxyl Radical; D066298:In Vitro Techniques; D007737:Kynurenine / Q000031:analogs & derivatives* / Q000378:metabolism; D008706:Methemoglobin / Q000378:metabolism*; D010084:Oxidation-Reduction; D013053:Spectrophotometry
D005609:Free Radicals; D006878:Hydroxides; C005045:3-hydroxykynurenine; D017665:Hydroxyl Radical; D007737:Kynurenine; D008706:Methemoglobin; D006861:Hydrogen Peroxide