Differential catalytic properties in metabolism of endogenous and exogenous substrates among CYP3A enzymes expressed in COS-7 cells

Biochim Biophys Acta. 1998 May 8;1380(3):297-304. doi: 10.1016/s0304-4165(97)00156-6.


The catalytic properties of CYP3A7 in the metabolism of endogenous and exogenous substrates were compared with those of CYP3A4 and CYP3A5 using COS-7 expressing enzymes. The highest activities of dehydroepiandrosterone (DHEA) and dehydroepiandrosterone 3-sulfate (DHEA-S) 16alpha-hydroxylase were observed in COS-7 cells expressing CYP3A7. In contrast, the activity of testosterone 6beta-hydroxylase of CYP3A7 expressed in COS-7 cells was much less than that of CYP3A4 expressed in COS-7 cells. The rate of carbamazepine 10, 11-epoxidation was the greatest in COS-7 cells expressing CYP3A4, followed by CYP3A5 and CYP3A7. On the other hand, the formation of reductive metabolite of zonisamide was the highest in COS-7 cells expressing CYP3A4, followed by CYP3A7 and CYP3A5. Furthermore, the addition of triazolam resulted in a decrease in 6beta-hydroxylation catalyzed by CYP3A7, but not by CYP3A4, whereas the pretreatment of microsomes with triacetyloleandomycin (TAO) resulted in a decrease in the reaction catalyzed by CYP3A4, but not by CYP3A7. Together with these results, it was suggested that CYP3A7 exerts differential catalytic properties not only in metabolism of endogenous substrates but also in drug metabolism compared to CYP3A4 and CYP3A5.

Publication types

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

MeSH terms

  • Adult
  • Animals
  • Aryl Hydrocarbon Hydroxylases*
  • COS Cells
  • Catalysis
  • Cytochrome P-450 CYP3A
  • Cytochrome P-450 Enzyme System / analysis
  • Cytochrome P-450 Enzyme System / biosynthesis*
  • Cytochrome P-450 Enzyme System / genetics
  • Cytochrome P-450 Enzyme System / metabolism*
  • DNA, Complementary / genetics
  • Dehydroepiandrosterone / metabolism
  • Enzyme Activation / drug effects
  • Genetic Vectors / metabolism
  • Humans
  • Mixed Function Oxygenases / metabolism
  • Oxidoreductases, N-Demethylating / biosynthesis*
  • Oxidoreductases, N-Demethylating / genetics
  • Oxidoreductases, N-Demethylating / metabolism*
  • Steroid 16-alpha-Hydroxylase
  • Steroid Hydroxylases / metabolism
  • Substrate Specificity
  • Testosterone / metabolism
  • Transfection
  • Triazolam / pharmacology
  • Troleandomycin / pharmacology


  • DNA, Complementary
  • Triazolam
  • Testosterone
  • Dehydroepiandrosterone
  • Cytochrome P-450 Enzyme System
  • Troleandomycin
  • Mixed Function Oxygenases
  • Steroid Hydroxylases
  • Aryl Hydrocarbon Hydroxylases
  • CYP3A protein, human
  • CYP3A5 protein, human
  • CYP3A7 protein, human
  • Cytochrome P-450 CYP3A
  • Steroid 16-alpha-Hydroxylase
  • CYP3A4 protein, human
  • Oxidoreductases, N-Demethylating