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THE KINETICS OF REDUCTION OF CYTOCHROME c BY SEMI‐REDUCED FLAVIN
Author(s) -
Salet C.,
Land E. J.,
Santus R.
Publication year - 1981
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1981.tb05485.x
Subject(s) - flash photolysis , chemistry , flavin mononucleotide , radiolysis , photochemistry , cytochrome c , cytochrome , reaction rate constant , flavin group , radical , kinetics , cytochrome c oxidase , electron transport chain , guanosine , organic chemistry , biochemistry , enzyme , physics , quantum mechanics , mitochondrion
— 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 ± 10 7 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.