TABLE 3.
Kinetic Analysis of UGT1A4-induced Glucuronidation of TAM, trans-4-OH-TAM and cis-4-OH-TAMa
| Substrate | UGT1A4 Variant | Vmax (pmol min−1 μg−1)b | Km (μM) | Vmax/Km (μl min−1 μg−1)b |
|---|---|---|---|---|
| trans-4-OH-TAM | UGT1A424Pro/48Leu | 62.4 ± 5.8 | 2.2 ± 0.4 | 29.3 ± 2.7 |
| UGT1A424Thr/48Leu | 54.9 ± 11.4 | 1.6 ± 0.1 | 33.2 ± 4.9 | |
| UGT1A424Pro/48Val | 49.3 ± 2.8 | 1.2 ± 0.1c | 40.8 ± 1.4d | |
| trans-TAM | UGT1A424Pro/48Leu | 68.0 ± 8.6 | 2.0 ± 0.51 | 35.2 ± 9.6 |
| UGT1A424Thr/48Leu | 62.1 ± 2.6 | 1.5 ± 0.20 | 41.0 ± 7.0 | |
| UGT1A424Pro/48Val | 52.1 ± 10.1 | 1.3 ± 0.10e | 40.1 ± 7.5 |
a
Data are expressed as mean ±SD for three independent experiments.
b
Data are expressed per μg UGT protein as determined by Western blot analysis. Values are significantly
c
P = 0.01,
d
P = 0.005 or
e
near-significantly (P = 0.053) different from that observed for microsomes from wild-type UGT1A424Pro/48Leu overexpressing cells.