ELECTRON-TRANSFER FROM PYRIDINYL RADICALS, HYDRATED ELECTRONS, CO2.- AND O2.- TO BACTERIAL CYTOCHROME P450

Several rate constants for one-electron reduction of cytochrome P450 are more rapid in the absence than in the presence of the specific substrate. The respective values for methyl viologen, nicotinamide adenine dinucleotide and the 1-methyl-4-(and -3-)carbamidopyridinium radicals are 2.6, 3.4, 6 and 35 × 107 M-1 s-1 without camphor, and 0.15, 0.1, 1.8 and 110 × 107 M-1 s-1 for the camphor complex. Hydrated electrons react with cytochrome P450 with a rate constant of 3.0 × 1010 M-1 s-1 whether camphor is bound or not, but little of the reduction takes place at the haem iron. No reduction of the haem iron by CO2•- or O2•- could be detected, whether camphor is bound or not. © 1979.