Comparison of cytochrome P-450 species which catalyze the hydroxylations of the aromatic ring of estradiol and estradiol 17-sulfate

J Steroid Biochem Mol Biol. 1991 Jun;38(6):737-43. doi: 10.1016/0960-0760(91)90087-l.


For identification of microsomal cytochrome P-450 (P-450) enzymes which catalyze 2- or 4-hydroxylations of estrogens in the rat liver, estradiol (E2) and estradiol 17-sulfate (E2-17-S) were selected as the substrates and incubated with various kinds of purified P-450 enzymes: PB-1, PB-2, PB-4 and PB-5 obtained from phenobarbital-treated male rats (Sprague-Dawley); MC-1 and MC-5 from 3-methylcholanthrene-treated male rats; and UT-1, UT-2, UT-4 and UT-5 from untreated animals. The reactions were carried out under the P-450-reconstructed system, and the resulting products were determined by HPLC using electrochemical detection. All the enzymes tested were shown to have varying degrees of catalytic activities for 2-hydroxylation of the two substrates; UT-1 and UT-2 had the highest activity. Of the induced P-450 enzymes, PB-2 and MC-1 showed fairly high catalytic activity for 4-hydroxylation of E2. The P-450 enzymes obtained from the untreated male rats, especially UT-4, showed the highest catalytic activity for 4-hydroxylation of the two substrates. From these results and also from kinetic experiments, the P-450 enzymes which catalyze 2- and 4-hydroxylations of estrogen were considered to be different species. A part of E2 was converted to such metabolites as estrone and those having a hydroxyl group at positions 6 beta, 15 alpha or 16 alpha, each production of which was estimated to be catalyzed by single or multiple P-450s.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Chromatography, High Pressure Liquid
  • Cytochrome P-450 Enzyme System / metabolism*
  • Estradiol / analogs & derivatives*
  • Estradiol / metabolism*
  • Estrogens, Catechol
  • Hydroxylation
  • Kinetics
  • Male
  • Methylcholanthrene / pharmacology
  • Microsomes, Liver / enzymology*
  • Phenobarbital / pharmacology
  • Rats
  • Rats, Inbred Strains


  • Estrogens, Catechol
  • estradiol 17-sulfate
  • Estradiol
  • Methylcholanthrene
  • 2-hydroxyestradiol 17-sulfate
  • Cytochrome P-450 Enzyme System
  • 4-hydroxyestradiol 17-sulfate
  • 2-hydroxyestradiol
  • 4-hydroxyestradiol
  • Phenobarbital