Spin state control of the hepatic cytochrome P450 redox potential

S. G. Sligar, D. L. Cinti, G. G. Gibson, J. B. Schenkman

Research output: Contribution to journalArticlepeer-review


We have measured the oxidation-reduction potential of isolated and partially purified cytochrome P450 from uninduced rat liver, both in the presence and absence of Type I substrates. Native P450 is found to have a potential of -300 mV with respect to the standard hydrogen electrode, while the addition of benzphetamine or hexabarbital increases the redox potential to -237 mV and -225 mV respectively. Quantitation of the thermally induced S = 1 2 to S = 5 2 spin transition of the ferric heme iron for this P450 preparation both substrate free as well as with bound benzphetamine and hexabarbital indicate an increase in the high spin (S = 5 2) fraction on the binding of Type I substrates. The relevant oxidation-reduction equilibria of the heme chromaphore are presented in terms of a thermodynamic model for the control of the observed cytochrome P450 redox potential through this modulation of the spin configuration of the five d-electrons of the ferric heme iron induced by the binding of Type I substrates.

Original languageEnglish (US)
Pages (from-to)925-932
Number of pages8
JournalBiochemical and Biophysical Research Communications
Issue number3
StatePublished - Oct 12 1979
Externally publishedYes

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology


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