Substrate | Km or S50 (µM) | Vmax | Clintd or Clmaxe |
---|---|---|---|
μM | pmol/min/mg | µl/min/mg | |
(S,S)-hydroxybupropion glucuronidea | 172 ± 38.9 | 739 ± 59.6 | 4.31 |
(R,R)-hydroxybupropion glucuronidea | 488 ± 98.3 | 5550 ± 507 | 11.4 |
(1R,2R)-hydrobupropion glucuronideb | 343 ± 37.5 | 3290 ± 269 | 7.7 |
(1S,2S)-hydrobupropion glucuronideb | 248 ± 27.1 | 358 ± 25.5 | 1.1 |
EGLUC1c | 373 ± 63.0 | 1740 ± 212 | 3.1 |
EGLUC2c | 360 ± 55.2 | 2280 ± 241 | 3.8 |
Values represent the parameter estimate ± S.E. obtained by fitting the Michaelis-Mentena (hydroxybupropion) or Hill.
↵b Glucuronide 1 and glucuronide 2 denoted based on retention times in Figs. 1–3 and outlined in Table 2. Erythro-hydrobupropion glucuronide (EGLUC).
↵c (threo- and erythro-hydrobupropion) equation to [substrate] versus metabolite formation velocity using Phoenix WinNonlin (version 6.4).
↵d Intrinsic clearance (Clint), calculated as the ratio of Vmax to Km.
↵e Maximal clearance (Clmax), calculated as the ratio of Vmax × (h − 1) to S50 + h(h − 1)1/h.