Reversible modification of cysteine residues of NADPH-cytochrome P-450 reductase

Biochem Biophys Res Commun. 1993 Jun 30;193(3):1044-8. doi: 10.1006/bbrc.1993.1730.


A reversible chemical modification of SH-groups of NADPH-cytochrome P-450 reductase is the subject of the present study. The enzyme was modified using first biradical RS-SR (R being the imidazolidine derivative) and a new affinity reductase inhibitor beta-cystamine adenosine diphosphate (ANSSN). These reagents were shown to be covalently bound to reductase SH-groups via the reaction of thiol-disulfide exchange resulting in the loss of reducing activity for cytochrome c. NADP+ protected reductase from inactivation and decreased the extent of the modification by RS-SR. The modification of reductase was reversible: the modified enzyme was partially reactivated with glutathione and dithiothreitol. The method proposed can be used to study both the reductase structure and the reversible inhibition of microsomal monooxygenase systems.

MeSH terms

  • Adenosine Diphosphate / analogs & derivatives
  • Adenosine Diphosphate / pharmacology*
  • Animals
  • Binding Sites
  • Cystamine / pharmacology*
  • Cysteine*
  • Electron Spin Resonance Spectroscopy
  • Kinetics
  • Microsomes, Liver / enzymology*
  • NADH Dehydrogenase / antagonists & inhibitors
  • NADH Dehydrogenase / metabolism*
  • NADPH-Ferrihemoprotein Reductase / antagonists & inhibitors
  • NADPH-Ferrihemoprotein Reductase / metabolism*
  • Rats


  • Adenosine Diphosphate
  • NADPH-Ferrihemoprotein Reductase
  • NADH Dehydrogenase
  • Cysteine
  • Cystamine