Kinetic parameters of AFQ N-glucuronidation in recombinant UGT isoforms and in human liver (HLM) and jejunum microsomes (HJM)
AFQ (15.6-4000 μM) was incubated with microsomes and UDP-glucuronic acid for 45 min. The kinetic parameters were calculated with GraphPad Prism software. Each value represents best-fit values ± S.E. of triplicate points. Kinetic plots are presented in Fig. 5.
Enzymes | Km or S50 | Vmax | CLinta or CLmaxb | Ksi c |
|---|---|---|---|---|
| μM | pmol/min/mg protein | μl/min/mg protein | μM | |
| HLMd | 2019 ± 85.9 | 871 ± 17.9 | 0.432 | |
| HJMd | 281 ± 17.3 | 111 ± 1.9 | 0.396 | |
| UGT1A1ef | 394 ± 16.6 | 36 ± 0.7 | 0.047 | |
| UGT1A3g | 355 ± 94.0 | 120 ± 13.7 | 0.337 | |
| UGT1A3h | 1959 ± 1448 | 502 ± 323 | 0.256 | 332 ± 248 |
| UGT1A4ei | 1547 ± 54.3 | 799 ± 14.5 | 0.304 |
|
↵ a CLint calculated as Vmax/Km for both Michaelis-Menten and substrate inhibition kinetics.
↵ b CLmax calculated as described under Materials and Methods.
↵ c Ksi = substrate inhibition constant.
↵ d Michaelis-Menten.
↵ e Hill equation.
↵ f n = 1.75 ± 0.102 from Hill equation.
↵ g Michaelis-Menten with the activity at 15.6 to 1000 μM substrate concentration.
↵ h Substrate inhibition.
↵ i n = 1.28 ± 0.025 from Hill equation.