Apparent kinetic parameters for the glucuronidation of fluoroquinolones by recombinant UGT1A1 and UGT1A9 enzymes For Km and Vmax values, glucuronidation activities from triplicate incubations were averaged and nonlinear regression was used to fit the data to the Michaelis-Menten equation. The parameter estimated and the S.E. value generated by the GraFit 5.0 software are shown.
Compound | Km | Vmax | Vmax/Km |
|---|---|---|---|
| mM | pmol/min/mg protein | (μl/min/mg) × 100 | |
| UGT1A1 | |||
| LVFX | 6.0 ± 0.97 | 19.5 ± 2.83 | 0.33 |
| GPFX | 2.7 ± 0.30 | 7.90 ± 0.74 | 0.29 |
| MFLX | 3.4 ± 0.21 | 312 ± 18.0 | 9.2 |
| STFX | 1.9 ± 0.13 | 87.4 ± 5.12 | 4.6 |
| UGT1A9 | |||
| LVFX | 2.6 ± 0.19 | 12.9 ± 0.76 | 0.50 |
| GPFX | 2.1 ± 0.10 | 141 ± 5.83 | 6.7 |
| MFLX | 2.1 ± 0.13 | 11.4 ± 0.59 | 0.54 |
| STFX | 6.3 ± 0.94 | 187 ± 26.0 | 3.0 |