title: The binding of carbon monoxide to cytochrome c oxidase.
abstract: The effect of CO on the optical absorbance spectrum of partially reduced cytochrome c oxidase  has been studied. The changes at 432 and 590 nm suggest that the cytochrome alpha2/3+ - CO compound is formed preferentially and that concomitantly a second electron is taken up by the enzyme. From the CO-induced changes at 830 nm it is concluded that in the partially reduced enzyme addition of CO causes reoxidation of the copper component of cytochrome c oxidase. Addition of CO to partially reduced enzyme (2 electrons per 4 metal ions) also brings about a decrease in the intensities of electron paramagnetic resonance signals of high-spin heme iron near g = 6 and of the low-spin heme at g = 2.6. Concomitantly both the low-spin heme a signal at g = 3 and the copper signal at g = 2 increase in intensity. These results demonstrate that formation of the reduced diamagnetic cytochrome a3 - CO compound is accompanied by reoxidation of both the copper component detectable by electron paramagnetic resonance and possibly also by cytochrome a.
mesh_terms: D000818:Animals; D001665:Binding Sites; D002248:Carbon Monoxide / Q000494:pharmacology; D002417:Cattle; D003574:Cytochrome c Group; D004578:Electron Spin Resonance Spectroscopy; D003576:Electron Transport Complex IV / Q000378:metabolism; D009206:Myocardium / Q000201:enzymology; D010084:Oxidation-Reduction; D011485:Protein Binding; D011487:Protein Conformation; D013053:Spectrophotometry
chemical_list: D003574:Cytochrome c Group; D002248:Carbon Monoxide; D003576:Electron Transport Complex IV