Correlations between spin equilibrium shift, reduction rate, and N-demethylation activity in liver microsomal cytochrome P-450 and a series of benzphetamine analogues as substrates

Biochem Pharmacol. 1983 Jun 1;32(11):1683-8. doi: 10.1016/0006-2952(83)90109-0.


Cytochrome P-450 forms a thermal ferric spin equilibrium which is significantly shifted by substrate binding. Within a series of benzphetamine analogues the liver microsomal enzyme system exhibits a close correlation of the substrate induced spin equilibrium shift towards the high spin state and both the rate of P-450 reduction, and of substrate turnover, as well. The spin equilibrium regulates the first electron transfer by favoured high spin state reduction and rapid pre-equilibration with respect to the low spin fraction.

MeSH terms

  • Animals
  • Benzphetamine / analogs & derivatives
  • Benzphetamine / pharmacology*
  • Chemical Phenomena
  • Chemistry
  • Cytochrome P-450 Enzyme System / isolation & purification*
  • Electron Transport
  • Kinetics
  • Male
  • Microsomes, Liver / enzymology*
  • Oxidation-Reduction / drug effects
  • Oxidoreductases, N-Demethylating / isolation & purification*
  • Phenethylamines / pharmacology*
  • Rats
  • Rats, Inbred Strains
  • Spectrophotometry
  • Substrate Specificity


  • Phenethylamines
  • Benzphetamine
  • Cytochrome P-450 Enzyme System
  • Oxidoreductases, N-Demethylating