The one-electron reduction potential of several substrates can be related to their reduction rates by cytochrome P-450 reductase.
The rates of reduction of 27 compounds by purified cytochrome P-450 reductase have been studied and correlated with the one-electron reduction potentials E7(X/X.-). For compounds with reduction potentials between approx. -400 and -165 mV, there was a good correlation between the rates and E7(X/X.-); log rate (mumol/min per mg) = (2.38 +/- 0.08) + (0.0061 +/- 0.0003)E7 (mV). Compounds with potentials more positive than -165 mV were shown to deviate from the correlation. It is shown that under the standard conditions of the assay, these compounds undergo two-electron reduction by NADPH rather than one-electron reduction with the enzyme. As a consequence of the study, the rate constants for the reaction of superoxide radicals with native and acetylated cytochrome c were also determined to be (4.5 +/- 0.5).10(5) and (1.5 +/- 0.15).10(5) M-1 s-1, respectively.
CRC Department of Biophysical Chemistry, Paterson Institute for Cancer Research, Christie Hospital, NHS Trust, Manchester, UK.
J
J
Butler
B M
BM
Hoey
D003574:Cytochrome c Group / Q000737:chemistry; D004583:Electrons; D007700:Kinetics; D009247:NADH, NADPH Oxidoreductases / Q000737:chemistry* / Q000302:isolation & purification; D010084:Oxidation-Reduction; D013481:Superoxides / Q000737:chemistry
D003574:Cytochrome c Group; D013481:Superoxides; D009247:NADH, NADPH Oxidoreductases; C069506:NADH-cytochrome P-450 reductase