Enzyme kinetic parameters for TSU-68 hydroxylation by human liver and cDNA-expressed P450 isoform microsomes
Microsomes | Km | Vmax | Vmax/Km | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| M1 | M2 | M3 | M1 | M2 | M3 | M1 | M2 | M3 | |||||||
| μM | pmol/min/mg protein | μl/min/mg protein | |||||||||||||
| Human liver microsomes | |||||||||||||||
| HLM 31 | 3.9 | 3.6 | 4.2 | 70 | 132 | 32 | 18.0 | 36.8 | 7.6 | ||||||
| HLM 74 | 8.5 | 8.0 | 8.9 | 31 | 55 | 14 | 3.7 | 6.9 | 1.6 | ||||||
| HLM 81 | 7.3 | 7.2 | 7.2 | 85 | 153 | 36 | 11.7 | 21.4 | 4.9 | ||||||
| HLM 94 | 7.2 | 8.2 | 7.6 | 137 | 275 | 59 | 19.0 | 33.4 | 7.8 | ||||||
| Mean ± S.D. | 6.7 ± 2.0 | 6.8 ± 2.2 | 7.0 ± 2.0 | 81 ± 44 | 154 ± 91 | 35 ± 18 | 13.1 ± 7.0 | 24.6 ± 13.5 | 5.5 ± 2.9 | ||||||
| μM | pmol/min/pmol P450 | μl/min/pmol P450 | |||||||||||||
| cDNA-expressed P450 | |||||||||||||||
| CYP1A1 | 0.76 | 0.86 | —a | 28.0 | 30.5 | 0.8 | 36.8 | 35.5 | — | ||||||
| CYP1A2 | 10.4 | 11.2 | 11.0 | 7.8 | 25.7 | 4.7 | 0.75 | 2.29 | 0.43 | ||||||
| CYP2C8 | 57.8 | 66.0 | 44.7 | 0.42 | 0.09 | 0.06 | 0.0073 | 0.0014 | 0.0014 | ||||||
↵ a —, not calculated.