J. Biol. Chem., Vol. 261, Issue 28, 13031-13033, 10, 1986
Redox-cycled oxidase. One of the reaction products of reduced cytochrome c, cytochrome c oxidase, and dioxygen [published erratum appears in J Biol Chem 1987 May 5;262(13):6438]
LJ Young and G Palmer
Pulsed and oxygenated forms of cytochrome c oxidase are believed to be
variants of the oxidized enzyme. They were produced as a consequence of one
or more reduction-oxidation cycles of the resting form and are
characterized by an increase of the alpha band intensity and a red- shift
of the Soret absorption band to 428 nm. The rate of decay of these species
back to the resting enzyme varies appreciably and appears to depend on the
nature of the reductant and/or oxidant used in their preparation. Here we
report that if resting oxidase is incubated with either reduced or oxidized
cytochrome c and then exposed to dioxygen, an activated form is rapidly
produced which appears to be more oxidized than the starting material. This
finding suggest some degree of partial reduction of the resting enzyme, but
this by itself cannot explain the extent of activation. Our results further
question the significance of the optical spectral "signature" of the
oxygenated (Okunuki, K., and Sekuzu, I. (1954) Seitaino Kagaka 5, 265-272),
pulsed (Antonini, E., Brunori, M., Colosimo, A., Greenwood, C., and Wilson,
M. T. (1977) Proc. Natl. Acad. Sci. U.S.A. 74, 3128-3132), and "420 nm"
species (Kumar, C., Naqui, A., and Chance, B. (1984) J. Biol. Chem. 259,
2073- 2076, 11668-11671), which are thought to be activated forms of
oxidized cytochrome c oxidase.
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