Table 1

Enzyme kinetic parameters for oxazepam glucuronidation by HLMs and expressed UGTs

	K_m	V_max	V_max/K_m	N	K_s	Model
	μM	pmol/min/mg	ml/min/kg		μM	(eq.^#)
S-Oxazepam Glucuronidation
LV12	58 ± 22	267 ± 58	4.6 ± 1.4	—^1-a	307 ± 113	3
LV21	43 ± 14	317 ± 42	7.3 ± 1.7	—^1-a	1496 ± 739	3
LV24	60 ± 20	325 ± 65	5.4 ± 1.4	—^1-a	261 ± 70	3
UGT2B15^*1-BV	35 ± 5	17 ± 2	0.49 ± 0.06	—^1-a	1247 ± 308	3
UGT2B15^*1-HK	29 ± 7	5 ± 1	0.16 ± 0.03	—^1-a	839 ± 516	3
UGT2B7	203 ± 123	1.8 ± 0.3	0.0091 ± 0.0036	—^1-a	—^1-a	1
UGT1A9	N.D.	N.D.	N.D.	N.D.	N.D.	N.D.
R-Oxazepam Glucuronidation
LV12	303 ± 25	95 ± 5	0.31 ± 0.02	—^1-a	—^1-a	1
LV21	273 ± 122	46 ± 10	0.17 ± 0.06	—^1-a	—^1-a	1
LV24	256 ± 15	163 ± 6	0.64 ± 0.03	—^1-a	—^1-a	1
UGT2B15^*1-BV	N.D.	N.D.	N.D.	N.D.	N.D.	N.D.
UGT2B15^*1-HK	N.D.	N.D.	N.D.	N.D.	N.D.	N.D.
UGT2B7	333 ± 82	7.0 ± 1.0	0.021 ± 0.004	2.2	—^1-a	2
UGT1A9	12 ± 3	2.7 ± 0.2	0.22 ± 0.04	—^1-a	3698 ± 1375	3

Oxazepam glucuronidation activities were measured as described underMaterials and Methods using HLMs (n = 3) and UGT isoforms expressed in either baculovirus infected insect cells (UGT1A9, UGT2B7, UGT2B15^*1-BV) or stably transfected HEK-293 cells (UGT2B15^*1-HK). Kinetic parameters were derived by fitting data to the appropriate kinetic model (eq. 1, 2, or 3). Values are given as the estimate ± the standard error of the estimate.

N.D., not determined since no activity was observed (quantitation limit 0.1 pmol/min/mg protein).
↵1-a —, parameter not present in kinetic model used to fit data.