The enzyme kinetic parameters for eight UGT1A isoenzymes with appropriate aglycone substrates
The initial rate data were fitted to eq. 2 omitting the high substrate concentrations with obvious substrate inhibition.
Enzyme | Vmax | Km (UDPGA) | KAX (UDPGA) | Km (Substrate) | Substrate |
|---|---|---|---|---|---|
| pmol min-1 mg-1 | μM | ||||
| UGT1A1 | 920 ± 35 | 409 ± 40 | 1402 ± 235 | 12.2 ± 1.77 | Ethinylestradiol |
| UGT1A3 | 6946 ± 149 | 371 ± 22.3 | 699 ± 25.7 | 500 ± 17.7 | Scopoletin |
| UGT1A4 | 5.89 ± 0.065 | 201 ± 6.20 | 342 ± 25.9 | 16.6 ± 0.738 | 1-Hydroxypyrene |
| UGT1A6 | 1261 ± 24.3 | 51.5 ± 3.26 | 163 ± 8.87 | 3.36 ± 0.134 | 1-Naphthol |
| 5386 ± 72.0 | 166 ± 6.63 | 252 ± 13.2 | 194 ± 6.42 | Scopoletin | |
| UGT1A7 | 13,821 ± 72.6 | 248 ± 3.17 | 316 ± 8.54 | 23.0 ± 0.355 | Entacapone |
| UGT1A8 | 2554 ± 87.3 | 1256 ± 75.5 | 1264 ± 130 | 20.7 ± 1.79 | 4-Hydroxyestrone |
| 2344 ± 84.6 | 875 ± 70.6 | 1159 ± 111 | 63.3 ± 4.97 | Entacapone | |
| UGT1A9 | 10,171 ± 51.9 | 388 ± 5.26 | 186 ± 6.90 | 20.7 ± 0.266 | Entacapone |
| 1849 ± 44.1 | 87.9 ± 5.97 | 111 ± 11.2 | 36.7 ± 2.09 | Scopoletin | |
| UGT1A10 | 4716 ± 70.5 | 670 ± 23.1 | 693 ± 48.7 | 28.9 ± 1.20 | Entacapone |