J. Biol. Chem., Vol. 259, Issue 17, 10777-10783, Sep, 1984

Carbon monoxide-driven reduction of ferric heme and heme proteins

D Bickar, C Bonaventura and J Bonaventura

Oxidized cytochrome c oxidase in a carbon monoxide atmosphere slowly becomes reduced as shown by changes in its visible spectra and its reactivity toward oxygen. The "auto-reduction" of cytochrome c oxidase by this procedure has been used to prepare mixed valence hybrids. We have found that this process is a general phenomenon for oxygen-binding heme proteins, and even for isolated hemin in basic aqueous solution. This reductive reaction may have physiological significance. It also explains why oxygen-binding heme proteins become oxidized much more slowly and appear to be more stable when they are kept under a CO atmosphere. Oxidized alpha and beta chains of human hemoglobin become reduced under CO much more slowly than does cytochrome c oxidase, where the CO-binding heme is coupled with another electron accepting metal center. By observing the reaction in both the forward and reverse direction, we have concluded that the heme is reduced by an equivalent of the water-gas shift reaction (CO + H2O----CO2 + 2e- + 2H+). The reaction does not require molecular oxygen. However, when the CO-driven reduction of cytochrome c oxidase occurs in the presence of oxygen, there is a competition between CO and oxygen for the reduced heme and copper of cytochrome alpha 3. Under certain conditions when both CO and oxygen are present, a peroxide adduct derived from oxygen reduction can be observed. This "607 nm complex," described in 1981 by Nicholls and Chanady (Nicholls, P., and Chanady, G. (1981) Biochim. Biophys. Acta 634, 256-265), forms and decays with kinetics in accord with the rate constants for CO dissociation, oxygen association and reduction, and dissociation of the peroxide adduct. In the absence of oxygen, if a mixture of cytochrome c and cytochrome c oxidase is incubated under a CO atmosphere, auto-reduction of the cytochrome c as well as of the cytochrome c oxidase occurs. By our proposed mechanism this involves a redistribution of electrons from cytochrome alpha 3 to cytochrome alpha and cytochrome c.
CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				L. L. Pearce, B. R. Pitt, and J. Peterson The Peroxynitrite Reductase Activity of Cytochrome c Oxidase Involves a Two-electron Redox Reaction at the Heme a3-CuB Site J. Biol. Chem., December 10, 1999; 274(50): 35763 - 35767. [Abstract] [Full Text] [PDF]

				C. Bonaventura, G. Godette, S. Tesh, D. E. Holm, J. Bonaventura, A. L. Crumbliss, L. L. Pearce, and J. Peterson Internal Electron Transfer between Hemes and Cu(II) Bound at Cysteine beta 93 Promotes Methemoglobin Reduction by Carbon Monoxide J. Biol. Chem., February 26, 1999; 274(9): 5499 - 5507. [Abstract] [Full Text] [PDF]

				H. Zhu, D. W. Ownby, C. K. Riggs, N. J. Nolasco, J. K. Stoops, and A. F. Riggs Assembly of the Gigantic Hemoglobin of the Earthworm Lumbricus terrestris. ROLES OF SUBUNIT EQUILIBRIA, NON-GLOBIN LINKER CHAINS, AND VALENCE OF THE HEME IRON J. Biol. Chem., November 22, 1996; 271(47): 30007 - 30021. [Abstract] [Full Text] [PDF]