THE INTERACTION OF CYTOCHROME-OXIDASE WITH HYDROGEN-PEROXIDE - THE RELATIONSHIP OF COMPOUND-P AND COMPOUND-F

Upon reaction of cytochrome oxidase with hydrogen peroxide, the spectr al changes are complete, with slightly less than 1 equiv of hydrogen p eroxide per cytochrome oxidase. At pH 8 the product is a mixture of th e P and F forms, while at pH 6 the product is exclusively the F form. These data are inconsistent with current interpretations of the struct ure of compounds P and F. Two stable radical species are detected by E PR; the relative amounts of these species are pH dependent. The MCD sp ectra of pure P and F are reported. It is suggested that compound F is a hydrogen peroxide adduct of cytochrome oxidase with cytochrome a(3) in the low-spin state and that compound P is an oxyferryl state of cy tochrome a(3) in support of the recent Raman data of Proshlyakov et al . [(1994) J. Biol. Chem. 269, 29385-29388]. We also suggest that coppe r B is in the trivalent state in compound P.