Kinetic analysis data for UGT1A4 and variant UGT1A4-P24T (UGT1A4*2)
Enzyme kinetics constants are presented with standard errors and 95% confidence intervals in parentheses. The rates were corrected (normalized) for relative expression levels (see Materials and Methods), and the extra sum-of-squares (F test in GraphPad Prism) was used for the calculation of Vmax differences as P values. The kinetic models that were used for the calculation of the constants are presented.
| UGT Enzyme | Km ± S.E. (95% Confidence Intervals) | Vmax ± S.E. (95% Confidence Intervals) | Hill Coefficient, h ± S.E. (95% Confidence Intervals) | Model, r2 |
|---|---|---|---|---|
| µM | relative velocity units/total protein concentrationa | |||
| Dexmedetomidine | ||||
| 1A4 | 387.7 ± 17.4 (351.5–423.9) | 312.0 ± 7.8 (295.8–328.1) | 1.8 ± 0.1 (1.6–2.1) | HE, 0.99 |
| 1A4-P24T | 371.0 ± 20.8 (327.6–414.3) | 34.1 ± 1.0 (31.9–36.3)* | 2.1 ± 0.2 (1.7–2.5) | HE, 0.98 |
| Trifluoperazine | ||||
| 1A4 | 52.0 ± 4.5 (42.7–61.2) | 366.8 ± 11.3 (343.4–390.3) | MM, 0.99 | |
| 1A4-P24T | 42.7 ± 6.4 (29.4–55.9) | 29.1 ± 1.4 (26.1–32.1)** | MM, 0.95 |
HE, Hill equation; MM, Michaelis-Menten equation.
↵a The rates were calculated as pmol glucuronide/min per mg total protein (using standard curves made with parent compounds’ UV absorption maxima) and corrected for relative expression levels of recombinant UGT1A4 and UGT1A4-P24T for a more reliable comparison (see Materials and Methods).
↵* P < 0.05; **P < 0.01.