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FEBS Lett. 2004 Jul 16;570(1-3):161-5.

The intrinsic stability of the second intermediate following the dioxygen-bound form in the O2 reduction by cytochrome c oxidase.

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Chemistry Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA.


Aeration of a two-electron reduced cytochrome c oxidase provides a species with two Raman bands at 804 and 356 cm(-1), identifying it as the second intermediate following the O2-bound species in the enzymatic O2 reduction process. It degrades directly to the fully oxidized form with a half-life time of 70 min at pH 8.0. The stability suggests an effective insulation for the active site in an extremely high oxidation state (Fe4+ with one oxidative equivalent nearby) against spontaneous electron leaks, which would dissipate proton motive force. The formation and degradation of the second intermediate are pH-dependent.

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