Annual Review 2001

Resonance Raman and absorption spectra were examined for the species generated upon incubation of oxidized bovine cytochrome c oxidase at pH 8.0 with carbon monoxide in the presence or absence of O2. The anaerobic incubation yielded the CO isotope sensitive bands at 517 and 578 cm–1 for 12C16O, at 512 and 563 cm–1 for 13C16O, at 508 and 574 cm–1 for 12C18O, and at 503 and 557 cm–1 for 13C18O, indicating the formation of heme a3CO adduct. The aerobic incubation with CO employing both O2 and O2 yielded the oxygen isotope-sensitive bands at 804 and 768 cm–1, respectively. These bands were identified by excitation at 441.6 and 607 nm but not at 413.1, 421.3, and 590 nm, a result which is consistent with the P intermediate absorption maxima occurring near 439 and 607 nm. The frequencies of the oxygen isotope sensitive bands are in agreement with those observed for the P intermediate in the O2 reduction by the fully reduced enzyme and in the H2O2 reduction by the oxidized enzyme. The other ironoxo species, the F intermediate, observed for both of the above referenced reactions was not generated in this study.