TABLE 3

Apparent kinetic parameters of luteolin glucuronidation and methylation obtained from RLS9 in UGT–COMT coreactions

Calculations were based on curve fitting using the Michaelis–Menten equation, substrate inhibition, or autoactivation model, as described in Materials and Methods. Data are expressed as the mean ± S.D., n = 3.

MetabolitesKm (μmol/L)Vmax (nmol/mg/min)CLint (mL/min/mg)Ki (μmol/L)
Lut-7-Ga9.9 ± 1.62.58 ± 0.110.26 ± 0.03
Lut-4′-Ga2.9 ± 0.30.69 ± 0.010.24 ± 0.02
Lut-3′-Ga11.5 ± 0.63.08 ± 0.050.27 ± 0.02
Chr-7-Gb7.3 ± 1.80.17 ± 0.020.02 ± 0.0159 ± 17
Dio-7-Gc9.4 ± 6.00.90 ± 0.400.11 ± 0.03
Chr-4′-Gb12.4 ± 4.50.24 ± 0.060.02 ± 0.0118 ± 7
Dio-3′-Gc44.4 ± 6.80.24 ± 0.020.01 ± 0.01
Chrysoeriolc1.3 ± 0.91.04 ± 0.181.16 ± 0.86
Diosmetinc6.6 ± 0.42.59 ± 0.150.39 ± 0.01
  • a Michaelis–Menten equation.

  • b Substrate inhibition equation.

  • c Autoactivation equation.