Nifedipine and midazolam oxidation activities in a reconstitution system, CYP3A4/NPR membranes, microsomes containing recombinant CYP3A4/NPR, and human liver microsomes5-a
| CYP3A4 System5-b | Nifedipine Oxidation | Midazolam | |
|---|---|---|---|
| 4-Hydroxylation | 1′-Hydroxylation | ||
| nmol products/min/nmol CYP3A4 | |||
| Reconstitution5-c | 29 | 9.0 | 13 |
| E. coli membranes | 35 | 13 | 16 |
| Lymphoblastoid cell microsomes | 11 | 3.2 | 4.6 |
| Baculosomes | 40 | 10 | 13 |
| Supersomes | 48 | 17 | 21 |
| Human liver microsomes | 34 | 12 | 17 |
↵5-a Nifedipine (200 μM) and midazolam (100 μM) were incubated with CYP3A4 (0.010 μM) for 5 min, and product formation was determined by HPLC. Data are the means of duplicate determinations.
↵5-b The enzyme source was the same as in Table 4. Purified humanb5 (1:1 molar ratio compared with CYP3A4) and rabbit NADPH-P-450 reductase (2-fold molar excess compared with CYP3A4) were added with 0.25 mM sodium cholate.
↵5-c Reconstitution systems containing purified CYP3A4 (0.010 μM), rabbit NPR (0.020 μM), and human b5 (0.010 μM) with lipid mixture (20 μg/ml) and cholate (0.25 mM).