Characterization of the oxidative metabolites of 17beta-estradiol and estrone formed by 15 selectively expressed human cytochrome p450 isoforms

Endocrinology. 2003 Aug;144(8):3382-98. doi: 10.1210/en.2003-0192.


We systematically characterized the oxidative metabolites of 17beta-estradiol and estrone formed by 15 human cytochrome P450 (CYP) isoforms. CYP1A1 had high activity for 17beta-estradiol 2-hydroxylation, followed by 15alpha-, 6alpha-, 4-, and 7alpha-hydroxylation. However, when estrone was the substrate, CYP1A1 formed more 4-hydroxyestrone than 15alpha- or 6alpha-hydroxyestrone, with 2-hydroxyestrone as the major metabolite. CYP1A2 had the highest activity for the 2-hydroxylation of both 17beta-estradiol and estrone, although it also had considerable activity for their 4-hydroxylation (9-13% of 2-hydroxylation). CYP1B1 mainly catalyzed the formation of catechol estrogens, with 4-hydroxyestrogens predominant. CYP2A6, 2B6, 2C8, 2C9, 2C19, and 2D6 each showed a varying degree of low catalytic activity for estrogen 2-hydroxylation, whereas CYP2C18 and CYP2E1 did not show any detectable estrogen-hydroxylating activity. CYP3A4 had strong activity for the formation of 2-hydroxyestradiol, followed by 4-hydroxyestradiol and an unknown polar metabolite, and small amounts of 16alpha- and 16beta-hydroxyestrogens were also formed. The ratio of 4- to 2-hydroxylation of 17beta-estradiol or estrone with CYP3A4 was 0.22 or 0.51, respectively. CYP3A5 had similar catalytic activity for the formation of 2- and 4- hydroxyestrogens. Notably, CYP3A5 had an unusually high ratio of 4- to 2-hydroxylation of 17beta-estradiol or estrone (0.53 or 1.26, respectively). CYP3A4 and 3A5 also catalyzed the formation of nonpolar estrogen metabolite peaks (chromatographically less polar than estrone). CYP3A7 had a distinct catalytic activity for the 16alpha-hydroxylation of estrone, but not 17beta-estradiol. CYP4A11 had little catalytic activity for the metabolism of 17beta-estradiol and estrone. In conclusion, many human CYP isoforms are involved in the oxidative metabolism of 17beta-estradiol and estrone, with a varying degree of catalytic activity and distinct regioselectivity.

Publication types

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

MeSH terms

  • Aryl Hydrocarbon Hydroxylases / metabolism
  • Catalysis
  • Chromatography, High Pressure Liquid
  • Cytochrome P-450 CYP1A1 / metabolism
  • Cytochrome P-450 CYP1A2 / metabolism
  • Cytochrome P-450 CYP1B1
  • Cytochrome P-450 CYP3A
  • Cytochrome P-450 Enzyme System / genetics
  • Cytochrome P-450 Enzyme System / metabolism*
  • Estradiol / metabolism*
  • Estrone / metabolism*
  • Gene Expression
  • Humans
  • Hydroxylation
  • Isoenzymes / metabolism*
  • NADP / pharmacology
  • Oxidation-Reduction
  • Substrate Specificity
  • Transfection


  • Isoenzymes
  • Estrone
  • Estradiol
  • NADP
  • Cytochrome P-450 Enzyme System
  • Aryl Hydrocarbon Hydroxylases
  • CYP1B1 protein, human
  • CYP3A protein, human
  • CYP3A5 protein, human
  • CYP3A7 protein, human
  • Cytochrome P-450 CYP1A1
  • Cytochrome P-450 CYP1A2
  • Cytochrome P-450 CYP1B1
  • Cytochrome P-450 CYP3A
  • CYP3A4 protein, human