Kinetic constants for the hSULT1E1-catalyzed sulfation of 4-OHTAM, N-desTAM, and endoxifen
The sulfation of each metabolite was determined using 0.86 µg purified hSULT1E1. Data were fit to a standard uncompetitive substrate inhibition equation and are the means ± S.E. from three independent experiments. Calculation of kcat values was based on 70,252 as the dimeric molecular mass of hSULT1E1.
| Metabolite | Km | Vmax | kcat/Km | Ki |
|---|---|---|---|---|
| µM | nmol/min/mg | min−1µM−1 | µM | |
| 4-OHTAM | 24 ± 5 | 12 ± 1 | 0.036 ± 0.008 | 387 ± 133 |
| Endoxifen | 24 ± 5 | 19 ± 2 | 0.057 ± 0.013 | 283 ± 86 |
| N-desTAM | 96 ± 52 | 26 ± 11 | 0.019 ± 0.013 | 144 ± 105 |