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Kinetic evidence for the re‐definition of electron transfer pathways from cytochrome c to O 2 within cytochrome oxidase
Author(s) -
Hill Bruce C.,
Greenwood Colin
Publication year - 1984
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(84)80113-1
Subject(s) - cytochrome c oxidase , cytochrome c , cytochrome c peroxidase , cytochrome , chemistry , coenzyme q – cytochrome c reductase , cytochrome c1 , electron transfer , cytochrome p450 reductase , electron transport complex iv , electron transport chain , cytochrome b , cytochrome b6f complex , photochemistry , oxidase test , stereochemistry , enzyme , biochemistry , mitochondrion , mitochondrial dna , gene
The reaction with O 2 of equimolar mixtures of cytochrome c and cytochrome c oxidase in high and low ionic strength buffers has been examined by flow‐flash spectrophotometry at room temperature. In low ionic strength media where cytochrome c and the oxidase are bound in an electrostatic, 1:1 complex some of the cytochrome c is oxidised at a faster rate than a metal centre of the oxidase. In contrast, when cytochrome c and cytochrome c oxidase are predominantly dissociated at high ionic strength cytochrome c oxidation occurs only slowly ( t =5 s) following the complete oxidation of the oxidase. These results demonstrate that maximal rates of electron transfer from cytochrome c to O 2 occur when both substrates are present on the enzyme. The heterogeneous oxidation of cytochrome c observed in the complex implies more than one route for electron transfer within the enzyme. Possibilities for new electron transfer pathways from cytochrome c to O 2 are proposed.