Reduction of Ferricytochrome c by Dithionite Ion: Electron Transfer by Parallel Adjacent and Remote Pathways
- 1 June 1973
- journal article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences
- Vol. 70 (6) , 1701-1703
- https://doi.org/10.1073/pnas.70.6.1701
Abstract
The kinetics of the reduction of horseheart ferricytochrome c by sodium dithionite (phosphate buffer-sodium chloride; pH 6.5, mu = 1.0, 25 degrees ) features two reaction pathways; one with the rate constant k(3) = 1.17 x 10(4) M(-1) sec(-1), the other with the rate constant k(1)k(2)/k(-1) = 6.0 x 10(4) M(-1) sec(-1). These pathways are interpreted in terms of remote attack (possibly by way of the exposed edge of the porphyrin system) and adjacent attack (requiring the opening of the heme crevice). The limiting rate for the adjacent pathway (k(1) = 30 sec(-1)) is in good agreement with the rate of heme-crevice opening of ferricytochrome c determined in other studies. The implication of the adjacent attack pathway to the function of cytochrome c in vivo is discussed.Keywords
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