Table 2. Kinetic parameters of M1 (quercetin-7-glucuronide) formation by single expressed UGT1A9*NHA and double expressed UGT1A1*1bCFP/1A9*NHA systems.
| 1A9*N or 1A1*1b/1A9*N | Km (μM) | Ksi (μM) | Vmax (pmol/min/unit) | CLint (μL/min/unit) | % of 1A9*NHA |
|---|---|---|---|---|---|
| 1A9*1HA | 9.10 ± 0.21 | 1.56 ± 0.06 | 791.3 ± 4.160 | 45.30 | 100 |
| 1A1*1bCFP/1A9*1HA | 14.87 ± 0.43*** | 1.93 ± 0.08 | 90.55 ± 0.47*** | 3.05*** | 6.7 |
| 1A9*2HA | 12.62 ± 1.97 | 257.6 ± 9.50 | 20.41 | 100 | |
| 1A1*1bCFP/1A9*2HA | 11.11 ± 1.84 | 45.93 ± 1.85*** | 4.13*** | 20.2 | |
| 1A9*3HA | 42.34 ± 8.23 | 768.2 ± 55.91 | 18.14 | 100 | |
| 1A1*1bCFP/1A9*3HA | 41.36 ± 7.71 | 328.8 ± 22.25** | 7.95** | 43.8 | |
| 1A9*5HA | 12.40 ± 1.43 | 68.02 ± 1.98 | 5.48 | 100 | |
| 1A1*1bCFP/1A9*5HA | 7.39 ± 1.16* | 16.87 ± 0.57*** | 2.28*** | 41.6 |
Asterisks indicate statistically significant differences compared with UGT1A9*NHA single expression systems (***P < 0.0001, **P < 0.005, *P < 0.05). Data are mean ± SD of three independent determinations.