TABLE 3

Kinetic parameters for TFP and LTG glucuronidation by UGT1A1(H39P), UGT1A6(H38P), UGT1A9(H37P), and UGT1A4

Data are presented as the parameter ± S.E. of parameter fit. Kinetic parameters are not corrected for relative expression or nonspecific binding.


UGT Enzyme

TFP Glucuronidationa

LTG Glucuronidationb
Km
Ksi
Vmax
Km
Vmax
μM pmol/min · mg μM pmol/min · mg
1A1 (H39P) 305 ± 1 87 ± 1 827 ± 2 774 ± 25 32 ± 1
1A6 (H38P) N.A. N.A. N.A. N.D. N.D.
1A9 (H37P) N.A. N.A. N.A. 3812 ± 239 628 ± 29
1A4
44 ± 1
369 ± 23
1164 ± 24
1579 ± 19
266 ± 2
  • N.A., no activity; N.D., not determined.

  • a Fit to substrate inhibition equation.

  • b Fit to Michaelis-Menten equation.