Electron redistribution in mixed valence cytochrome oxidase following photolysis of carboxy-oxidase.
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.
Harmon
H J
HJ
Department of Zoology, Oklahoma State University, Stillwater 74078.
D000818:Animals; D002151:Calorimetry; D002248:Carbon Monoxide / Q000378:metabolism; D002417:Cattle; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000378:metabolism*; D007700:Kinetics; D008929:Mitochondria, Heart / Q000201:enzymology*; D010782:Photolysis; D013053:Spectrophotometry
D002248:Carbon Monoxide; D003576:Electron Transport Complex IV