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  • Title: Electron redistribution in mixed valence cytochrome oxidase following photolysis of carboxy-oxidase.
    Author: Harmon HJ.
    Journal: J Bioenerg Biomembr; 1988 Dec; 20(6):735-48. PubMed ID: 2854130.
    Abstract:
    Absorbance changes at 446 nm in purified cytochrome oxidase following flash photolysis of carboxy-oxidase poised in the mixed valance state at +220 mV show biphasic kinetics. One phase corresponds to CO recombination to ferrous cytochrome a3 with an energy of activation of 9 kcal/mol; the second phase is 3-5 times faster with an energy of activation of 9.15 kcal/mol. Following flash photolysis at approximately -60 degrees C, cytochromes a and c and the 840-nm CuA species are observed to undergo reduction as electrons from ferrous unliganded cytochrome a3 equilibrate with the equipotential redox centers of the oxidase; as CO recombines with ferrous cyochrome a3, these centers are oxidized and the mixed valence carboxy-oxidase is regenerated. Electron redistribution between centers of the oxidase in the forward and reverse directions occurs faster than does the binding of CO.
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