Table 4

Kinetic parameters of EGC glucuronidation in liver microsomes from humans, mice, and rats

Microsomes	EGC-3′-Gluc		EGC-7-Gluc
Microsomes	V_max	K_m	V_max/K_m	V_max	K_m	V_max/K_m
	pmol/mg/min	μM	μl/mg/min	pmol/mg/min	μM	μl/mg/min
Humans	98 ± 6	988 ± 93	0.10	N/D	N/D	N/D
Rats	5.9 ± 0.1	168 ± 12	0.035	69 ± 9	259 ± 85	0.27
Mice	223 ± 24	450 ± 101	0.50	216 ± 24	236 ± 70	0.91

Kinetic studies were conducted for 30 min using 2 mg/ml of tissue microsomal proteins in the presence of 1 mM UDPGA and with EGC concentrations ranging from 10 to 900 μM. The formation of EGC glucuronides was quantified with LC/MS/MS. The apparent kinetic parameters (K_m and V_max) of EGC glucuronidation were calculated with GraphPad Prism. The values represent best-fit values ± standard error.V_max and K_m values were used to determine the catalytic efficiency (V_max/K_m).

N/D, not detectable.