Psilocin and 4-hydroxyindole glucuronidation kinetics
The values represent a best-fit result ± S.E. The reaction velocity is presented both as actual rates and rates normalized to UGT1A10 expression level (i.e., for UGT1A10, the actual and normalized rates are identical). See Materials and Methods for additional details.
| Substrate | Enzyme | Km | Vmax (Actual Rates) | Vmax (Normalized Rates) | Kis | Kinetic Model (r2) |
|---|---|---|---|---|---|---|
| μM | nmol/min/mg | nmol/min/mg | μM | |||
| Psilocin | UGT1A10 | 3851.0 ± 166.6 | 2.53 ± 0.06 | Michaelis-Menten (0.997) | ||
| UGT1A9 | Km1 = 1017.0 ± 249.9a | Vmax1 = 0.38 ± 0.14a | Vmax1 = 0.19 ± 0.04a | Two-site biphasic (0.996) | ||
| 4OH-Indole | UGT1A10 | 3624.0 ± 839.7b | 3.36 ± 0.63b | 2603.0 ± 744.8 | Substrate inhibition (0.992) | |
| UGT1A6 | 178.7 ± 14.8 | 9.31 ± 0.45 | 4.78 ± 0.23 | 765.1 ± 65.5 | Substrate inhibition (0.991) | |
| UGT2A1 | 3210.0 ± 235.7 | 1.48 ± 0.06 | 0.39 ± 0.02 | Michaelis-Menten (0.992) |
↵a The calculated CLint is 1.69 × 10−4 ± 1.04 × 10−5 ml/min/mg (normalized, 8.29 × 10−5 ± 5.12 × 10−6 ml/min/mg) and represents the linear portion of the biphasic curve (ratio Vmax2/Km2). Data were also fitted to the Michaelis-Menten equation, Km = 12047 ± 1428 μM, Vmax = 3.41 ± 0.31 (normalized, 1.66 ± 0.15) nmol/min/mg, r2 = 0.996.
↵b Data were also fitted to the Hill equation, S50 = 631.6 ± 32.7 μM, Vmax = 1.03 ± 0.02 nmol/min/mg, Hill coefficient h = 1.60 ± 0.11, r2 = 0.986.