Activities of heterologously expressed CYP3A4, CYP3A5, and CYP3A7 towards in vitro phenotyping probes
Substrate concentrations can be found in the text. CYP3A4 and CYP3A7 are coexpressed with cytochrome b5 and oxidoreductase, whereas CYP3A5 is coexpressed with oxidoreductase only. Each experimental condition was conducted in triplicate, and the data presented are the mean (±S.D.) of two individual experiments. Ratios of testosterone 2α-hydroxylase to 6β-hydroxylase activities (T2αH/T6βH ratios) >1.2 imply that CYP3A7 is the predominant CYP3A isoform present.
CYP3A Isoform | Testosterone Metabolite Formation | T2αH/T6βH Ratio | DHEA 16α Hydroxylase | ||||
|---|---|---|---|---|---|---|---|
| 6β-OH | 2α-OH | 2β-OH | |||||
| pmol/min/pmol P450 | pmol/min/pmol | ||||||
| rCYP3A4 | 46.82 ± 0.08 | 0.32 ± 0.01 | 4.60 ± 0.28 | 0.007 | 10.6 ± 0.6 | ||
| rCYP3A5 | 1.70 ± 0.01 | 0.13 ± 0.01 | 0.22 ± 0.01 | 0.079 | 0.1 ± 0.02 | ||
| rCYP3A7 | 0.68 ± 0.06 | 0.80 ± 0.06 | 0.21 ± 0.01 | 1.186 | 13.8 ± 1.5 | ||