Table 3. Kinetic parameters of M2 (quercetin-3-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 | 7.74 ± 0.86 | 568.0 ± 13.30 | 37.08 | 100 | |
| 1A1*1bCFP/1A9*1HA | 10.29 ± 0.98* | 256.9 ± 36.17 | 135.9 ± 5.73*** | 13.21*** | 35.6 |
| 1A9*2HA | 3.65 ± 0.40 | 211.0 ± 3.54 | 57.89 | 100 | |
| 1A1*1bCFP/1A9*2HA | 4.02 ± 0.70 | 117.5 ± 16.94 | 88.35 ± 5.09* | 22.00*** | 38.0 |
| 1A9*3HA | 21.85 ± 4.80 | 195.7 ± 61.83 | 467.3 ± 57.26 | 21.39 | 100 |
| 1A1*1bCFP/1A9*3HA | 14.65 ± 2.77 | 147.0 ± 34.84 | 664.9 ± 64.76* | 45.39** | 212.2 |
| 1A9*5HA | 7.21 ± 1.39 | 34.75 ± 1.43 | 4.82 | 100 | |
| 1A1*1bCFP1A9*5HA | 4.13 ± 1.15* | 103.3 ± 23.16 | 30.73 ± 2.91 | 7.44** | 154.4 |
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.