Kinetic parameters for the formation of M4 and M5 from MNTX by liver cytosol of mice, rats, monkeys, and humans, and of 6β-naltrexol from naltrexone by human liver cytosol
| Substrate | Species | Km | Vmax | Vmax/Km | |||
|---|---|---|---|---|---|---|---|
| M4 | M5 | M4 | M5 | M4 | M5 | ||
| μM | μM | pmol/min/mg | pmol/min/mg | ml/min/mg | ml/min/mg | ||
| MNTX | Mouse | 1220 | 714 | 11.0 | 125 | 0.009 | 0.175 |
| Rat | N.D. | 396 | N.D. | 40.7 | N.D. | 0.103 | |
| Monkey | 391 | 266 | 80.0 | 21.9 | 0.20 | 0.082 | |
| Human | 361 | 793 | 43.7 | 62.5 | 0.12 | 0.079 | |
| 6β-Naltrexol | Human | 625 | 12.6 | ||||
| Naltrexone | Human | 49.7 | |||||
N.D., metabolite not detected.