THE KINETICS OF REDUCTION OF CYTOCHROME c BY SEMI-REDUCED FLAVIN |
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| Authors: | C. Salet E. J. Land R. Santus |
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| Affiliation: | Laboratoire de Biophysique, Museum National d'Histoire Naturelle, 61 Rue Buffon, 75005 Paris, France;Paterson Laboratories, Christie Hospital &Holt Radium Institute, Manchester, M20 9BX, UK;Laboratoire de Physico-Chimie de l'Adaptation Biologique, Museum National d'Histoire Naturelle. 43 Rue Cuvier, 75231 Paris Cedex 05, France |
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| Abstract: | Abstract— Flavin mononucleotide radicals, FMNH', generated by laser flash photolysis of FMN in the presence of the electron donors, histidine, guanosine monophosphate or EDTA, were found to reduce cytochrome c with an apparent rate constant of 6 ± 107 M −1 s−1. These flash photolysis results were, however, complicated by the electron donor radicals formed simultaneously which, particularly with EDTA, also lead to reduction of cytochrome c. Pulse radiolysis of a nitrous oxide saturated aqueous solution of FMN containing a high concentration of HCOONa, leads to the exclusive formation of FMNH'. By adding small concentrations of cytochrome c to this solution, a rate constant of 4.0 ± 10−1 M −1 s−1 was obtained for the reduction of cytochrome c by FMNH'. Replacement of the HCOONa by EDTA in such solutions leads to further routes for reduction of cytochrome c on radiolysis. as in the photolytic situation. The relevance of these results to flavin-photosensitised reduction of cytochrome c and other components of the mitochondrial electron transport chain is discussed. |
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