The Interaction of Cytochrome Oxidase with Hydrogen Peroxide: The Relationship of Compounds P and F. Marian Fabian and Graham Palmer

Biochemistry 34 1534-1540 (1995)..

SUMMARY. Upon reaction of cytochrome oxidase with hydrogen peroxide the spectral changes are complete with slightly less than 1 equivalent of hydrogen peroxide per cytochrome oxidase. At pH 8 the product is a mixture of the P and F forms while at pH 6 the product is exclusively the F form. These data are inconsistent with current interpretations of the structure of compounds P and F. Two stable radical species are detected by epr; the relative amounts of these species are pH dependent. The mcd spectra of pure P and F are reported. It is suggested that compound F is a hydrogen peroxide adduct of cytochrome oxidase with cytochrome a3 in the low-spin state and that compound P is an oxyferryl state of cytochrome a3 in support of the recent Raman data of Proshlyakov et al. [(1994)J. Biol. Chem. 269, 29385-29388]. We also suggest that copper B is in the trivalent state in compound P.