Effects of source of b5 and other proteins on testosterone 6β-hydroxylation activities by CYP3A4/NPR membranes
| NPR Membrane | Added Component | Testosterone 6β-Hydroxylation |
|---|---|---|
| nmol/min/nmol P-450 | ||
| Experiment 1 | ||
| CYP3A4/NPR | 41 | |
| CYP3A4/NPR | Recombinant | 80 |
| human b 5 | ||
| CYP3A4/NPR | Humanb 5 | 78 |
| CYP3A4/NPR | Rabbitb 5 | 73 |
| CYP3A4/NPR | Ratb 5 | 70 |
| Experiment 2 | ||
| CYP3A4/NPR | 38 ± 4 | |
| CYP3A4/NPR | b 5 | 85 ± 9 |
| CYP3A4/NPR | apo b 5 | 82 ± 10 |
| CYP3A4/NPR | cytochrome c | 41 ± 6 |
| CYP3A4/NPR | CYP1A2 | 81 ± 7 |
| NPR | CYP1A2 | <0.1 |
In experiment 1, cytochrome b5 (0.020 μM) purified from E. coli membranes or from liver microsomes was added to CYP3A4/NPR membranes (0.010 μM P-450 and 0.020 μM NPR). In experiment 2, other proteins (0.010 μM) were added to CYP3A4/NPR membranes. Apo b5 and CYP1A2 were prepared from rabbit liver b5 and E. coli membranes expressing human CYP1A2, respectively. Results are presented as means ± S.D. of duplicate or triplicate determinations.