Kinetic parameters for MEGX and 3-OH-lidocaine formation in microsomes from two human livers
| MEGX | 3-OH-lidocaine | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Vmax12-a | Km1 | Vmax22-a | Km2 | n2-b | Vmax12-c | Km1 | Vmax22-c | Km2 | ||
| μM | μM | μM | μM | |||||||
| Without inhibitor2-d | HL20 | 3.82 | 228 | 2.30 | 813 | 3.1 | 13 | 6395 | 29 | 134 |
| HL22 | 8.32 | 270 | 12.21 | 2610 | 1.6 | 8 | 975 | 13 | 144 | |
| With TAO2-e | HL20 | 5.01 | 732 | 27 | 207 | |||||
| HL22 | 12.91 | 3777 | 21 | 478 | ||||||
| With furafylline2-f | HL20 | 6.20 | 1109 | 1.2 | 14 | 2758 | ||||
| HL22 | 29.41 | 5274 | 0.8 | 23 | 2007 | |||||
HL20 is a noninduced and HL22 an induced liver (see Table 1).
↵2-a In nanomoles per minute per milligram of protein.
↵2-b Hill coefficient for cooperative substrate binding (arbitrary units).
↵2-c In picomoles per minute per milligram of protein.
↵2-d Determined in incubations without chemical inhibitors. Data on MEGX formation were fitted with a two-enzyme model, consisting of a Michaelis-Menten equation and a Hill equation. Data on 3-OH-lidocaine formation were fitted with a two-enzyme model, consisting of two Michaelis-Menten equations.
↵2-e Determined in incubations with 100 μM TAO. Data on MEGX and 3-OH-lidocaine formation were fitted with a Michaelis-Menten model.
↵2-f Determined in incubations with 20 μM furafylline. Data on MEGX formation were fitted with a Hill enzyme model. Data on 3-OH-lidocaine formation were fitted with a Michaelis-Menten model.