Table 5

Correlation of CYP2B6 content with various CYP-catalyzed activities in a panel of human liver microsomes

Activity5-aCYP Isoforms Involvedr2n
Total CYP0.1514
Cytochrome creductase0.0114
EthoxycoumarinO-deethylaseMultiple0.62** 14
Phenacetin O-deethylaseCYP1A20.0014
Coumarin 7-hydroxylaseCYP2A60.64** 14
Mephenytoin 4′-hydroxylaseCYP2C190.0414
Chlorzoxazone 6-hydroxylaseCYP2E10.1314
Testosterone 6β-hydroxylaseCYP3A40.335-150 21
Lauric acid ω-hydroxylaseCYP4A0.17
Methoxychlorortho-hydroxylaseCYP2B6, CYP1A2, CYP3A4,5-bCYP2C195-c 0.53** 17
  • 5-150  Indicates statistical significance, p < .01; ** p < .001.

  • 5-a Isoform-specific catalytic activities were measured by the vendor (IIAM, Exton, PA), except for 7 additional livers (of 21 total), for which we determined testosterone 6β-hydroxylase and 17 livers for which we determined methoxychlor ortho-hydroxylase activities.

  • 5-b CYP3A4 contributes to total ortho-hydroxylase activity only after demethylation by CYP1A2 and CYP2C19 (Stresser and Kupfer, 1998a).

  • 5-c Inferred from studies with purified recombinant CYP2C19.