Multiple activated oxygen species in P450 catalysis: contributions To specificity in drug metabolism

Drug Metab Dispos. 1998 Dec;26(12):1190-3.


A hypervalent iron-oxene species has been widely proposed as the "active oxygen" in cytochrome P450 (P450)-catalyzed reactions. We recently examined the effect of mutation of the highly conserved threonine residue in P450s 2B4 and 2E1 to alanine, a change that is believed to interfere with proton delivery to the active site, and have determined the change in rates of deformylation of aldehydes, epoxidation of olefins, and hydroxylation of various substrates. The results support the concept that three distinct oxidants are functional in P450 catalysis: nucleophilic peroxo-iron, nucleophilic or electrophilic hydroperoxo-iron, and electrophilic oxenoid-iron. The occurrence of multiple oxidizing species may contribute to the remarkable versatility of the P450 family of isozymes in the modification of drugs and other substrates. Furthermore, the relative concentrations of these oxidants in a particular P450 isozyme may contribute to substrate specificity and govern the type of reaction catalyzed.

Publication types

  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Animals
  • Cytochrome P-450 Enzyme System / metabolism*
  • Humans
  • Pharmaceutical Preparations / metabolism*
  • Reactive Oxygen Species / metabolism*
  • Substrate Specificity


  • Pharmaceutical Preparations
  • Reactive Oxygen Species
  • Cytochrome P-450 Enzyme System