Determination of Vmaxa,b | ||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Enzymes and Metabolites | 2 μM | 10 μM | 20 μM | Mean Vmax | Vmax/Km | |||||||||||
V | Vmax | V | Vmax | V | Vmax | |||||||||||
mean ± S.D. | ||||||||||||||||
HLM | M4 | 15.7 | 1175 | 129 | 14550 | 165 | 18599 | 11441 ± 8781 | 0.68 | |||||||
M5 | 30.3 | 1231 | 132 | 1178 | 194 | 963 | 1124 ± 116 | 14.2c | ||||||||
M20 | 212 | 407 | 287 | 553 | 288 | 553 | 505 ± 85 | 3.6 | ||||||||
M24 | 10.2 | 53 | 30.3 | 158 | 52.2 | 272 | 161 ± 109 | 0.26 | ||||||||
CYP3A4 | M4 | 0.27 | 16 | 1.96 | 111 | 2.65 | 149 | 92 ± 69 | 0.82 | |||||||
M20 | 1.68 | 11 | 9.25 | 37 | 9.69 | 39 | 29 ± 16 | 4.8 | ||||||||
| M24 | 0.30 | 1.9 | 0.59 | 3.7 | 1.05 | 6.6 | 4.0 ± 2.3 | 0.4 |
↵ a The unit for V and Vmax was pmol/mg protein/min for HLM and pmol/pmol P450/min for CYP3A4. CYP3A4 content used was 76 pmol/mg in HLMs (Rostami-Hodjegan and Tucker, 2007). The unit for Vmax/Km was μl/min/pmol CYP3A4 for M4, M20, and M24.
↵ c The unit of Vmax/Km for M5 was μl/min/mg proteins for M5.