The oxidation of cytochrome c oxidase by hydrogen peroxide.
The reaction of H2O2 with mixed-valence and fully reduced cytochrome c oxidase was investigated by photolysis of fully reduced and mixed-valence carboxy-cytochrome c oxidase in the presence of H2O2 under anaerobic conditions. The results showed that H2O2 reacted rapidly (k = (2.5-3.1) X 10(4) M-1 X s-1) with both enzyme species. With the mixed-valence enzyme, the fully oxidised enzyme was reformed. On the time-scale of our experiments, no spectroscopically detectable intermediate was observed. This demonstrates that mixed-valence cytochrome c oxidase is able to use H2O2 as a two-electron acceptor, suggesting that cytochrome c oxidase may under suitable conditions act as a peroxidase. Upon reaction of H2O2 with the fully reduced enzyme, cytochrome a was oxidised before cytochrome a3. From this observation it was possible to estimate that the rate of electron transfer from cytochrome a to a3 is about 0.5-5 s-1.
Gorren
A C
AC
Dekker
H
H
Wever
R
R
D000818:Animals; D002417:Cattle; D017936:Cytochrome a Group; D003580:Cytochromes / Q000378:metabolism; D004579:Electron Transport / Q000528:radiation effects; D003576:Electron Transport Complex IV / Q000378:metabolism* / Q000528:radiation effects; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007700:Kinetics; D010084:Oxidation-Reduction / Q000528:radiation effects; D010782:Photolysis; D013057:Spectrum Analysis; D013379:Substrate Specificity
D017936:Cytochrome a Group; D003580:Cytochromes; D006861:Hydrogen Peroxide; D003576:Electron Transport Complex IV