TABLE 1.
CYP3A4 and CYPOR contents and NADPH-cytochrome c reductase activities of BTC3A4_POR membrane fractions
| BTC3A4_POR | CYP3A4 | CYPORa | Ratio CYPOR/CYP3A4 | Vmax Cytochrome cred | Electron Transfer Efficiencyb |
|---|---|---|---|---|---|
| pmol/mg protein | nmol · min−1 · mg protein−1 | ||||
| Null | 129 ± 2 | 0 | 2.1 ± 0.7 | ||
| WT | 77 ± 3 | 30.3 ± 1.5 | 1:3 | 97.1 ± 5.1 | 100 |
| P228L | 105 ± 28 | 37.8 ± 2.6 | 1:3 | 68.9 ± 2.9 | 55 (76) |
| M263V | 111 ± 11 | 24.4 ± 1.4 | 1:5 | 84.0 ± 0.4 | 105 (104) |
| A287P | 77 ± 8 | 16.3 ± 1.2 | 1:5 | 44.4 ± 5.3 | 85 (41) |
| G413S | 85 ± 13 | 24.0 ± 1.1 | 1:4 | 84.5 ± 5.2 | 108 (71) |
| Q153R | 58 ± 3 | 26.0 ± 2.7 | 1:2 | 84.2 ± 1.9 | 100 (23) |
| R457H | 53 ± 6 | 26.9 ± 1.3 | 1:2 | 27.1 ± 1.0 | 30 (8) |
| G539R | 127 ± 11 | 24.5 ± 1.0 | 1:5 | 5.0 ± 0.4 | 4 (41) |
| Y181D | 81 ± 6 | 36.2 ± 0.1 | 1:2 | 4.1 ± 0.7 | 2 (0) |
| Y459H | 75 ± 6 | 21.2 ± 0.7 | 1:4 | 10.1 ± 2.5 | 12 (7) |
| V492E | 50 ± 9 | 24.8 ± 1.6 | 1:2 | 3.5 ± 0.1 | 2 (7) |
| L565P | 120 ± 12 | 8.1 ± 0.6 | 1:14 | 3.0 ± 0.2 | 4 (29) |
| R616X | 104 ± 9 | 6.9 ± 0.3 | 1:14 | 2.5 ± 0.2 | 3 (0) |
| Human liver microsomes | 1:3 [1:2–1:13]c | ||||
CYPOR content of membranes, based on immunoblot analysis.
Percentage in electron transfer measured as NADPH cytochrome c reduction (Vmax) relative to the expected, calculated reduction activity based on the CYPOR protein content (immunodetection) using kcat of 3200 min−1 (Parikh et al., 1997). Numbers in parentheses indicate the same percentage, calculated by using the Vmax values, reported by Huang et al. (2005), with use of N-terminal (27 amino acids)-deleted CYPOR expression relatively to their CYPOR_WT form.
CYPOR/CYP3A ratio (average and interval) (Venkatakrishnan et al., 2000), assuming a ∼30% CYP3A content of human liver (Guengerich, 2005).