TABLE 1

Kinetic parameters for the in vitro glucuronidation of bile acids by recombinant human UGT2A1 and UGT2A2

Results are expressed as mean ± S.D. of two independent experiments performed in triplicate.

Substrate	Glucuronide	UGT2A1				UGT2A2
Substrate	Glucuronide	K_m	V_max	Kinetic profile (n)	CL_int.: V_max/K_m	K_m	V_max	Kinetic profile (n)	CL_int.: V_max./K_m
		µM	pmol/min/mg proteins		µl/min/mg^a	µM	pmol/min/mg proteins		µl/min/mg^a
CA	CA-24G	2344.8 ± 2245.6	83.3 ± 55.0	H (1.1 ± 0.1)	0.03	3442.9 ± 2921.2	2621.7 ± 1113.3	H (0.8 ± 0.1)	0.78
CDCA	CDCA-3G	1744.3 ± 1115.9	95.0 ± 45.0	MM	0.01	—	—	—	—
	CDCA-24G	1397.4 ± 711.5	536.7 ± 186.7	MM	0.38	143.6 ± 21.1	805.0 ± 36.7	MM	5.6
LCA	LCA-3G	102.2 ± 14.5	685.0 ± 45.0	H (1.9 ± 0.4)	6.71	107.1 ± 15.1	61.7 ± 3.3	H (1.2 ± 0.1)	0.57
	LCA-24G	102.3 ± 14.5	305.2 ± 241.7	H (1.8 ± 0.4)	2.98	113.7 ± 12.5	265.1 ± 13.3	H (1.6 ± 0.2)	2.33
DCA	DCA-3G	2405.6 ± 1236.0	83.3 ± 33.3	MM	0.03	178.3 ± 49.4	8.3 ± 1.7	MM	0.05
	DCA-24G	917.9 ± 204.3	235.2 ± 31.7	MM	0.25	189.0 ± 20.3	196.7 ± 10.2	H (1.7 ± 0.2)	1.03
HDCA	HDCA-6G	237.4 ± 37.5	45.1 ± 3.3	MM	0.18	150.4 ± 23.0	1373.3 ± 71.7	MM	9.13
	HDCA-24G	178.5 ± 24.0	805.1 ± 38.3	MM	4.52	226.1 ± 39.0	28.3 ± 1.7	MM	0.13
HCA	HCA-6G	—	—	—	—	222.4 ± 35.1	65.1 ± 3.3	MM	0.30
	HCA-24G	210.7 ± 71.2	495.1 ± 80.0	H (1.3 ± 0.3)	2.35	465.8 ± 56.6	911.7 ± 55.1	MM	1.95

CA, cholic acid; CDCA, chenodeoxycholic acid; DCA, deoxycholic acid; H, Hill (i.e., sigmoidal) kinetic profile; HCA, hyocholic acid; HDCA, hyodeoxycholic acid; LCA, lithocholic acid; MM, Michaelis-Menten kinetic profile; (n), Hill coefficient.
↵^a That is, µl/min/mg of total proteins from the recombinant system.