TABLE 1

Kinetic parameters for midazolam metabolism by liver and intestinal microsomes

All values are the means of three independent experiments ± S.D. Incubations were performed as described under Materials and Methods.

Microsomes and Strains	1′-OH Midazolam					4-OH Midazolam
Microsomes and Strains		K_m	V_max	V_max/K_m	K_m	V_max	V_max/K_m
	μM	pmol/min/mg protein	μL/min/mg protein	μM	pmol/min/mg protein	μL/min/mg protein
Liver
Cyp3a ^+/+	0.95 ± 0.18	630 ± 29	662	8.43 ± 0.27	224 ± 12.7	26.6
Cyp3a ^−/−	6.38 ± 1.2	735 ± 11	115	17.5 ± 6.9	49.8 ± 5.0	2.36
Human	2.93 ± 0.33	2097 ± 155	715	38.7 ± 6.3	1226 ± 87	27.8
Intestine
Cyp3a ^+/+	10.4 ± 1.8	62.3 ± 3.2	6.02	55.9 ± 2.0	38.0 ± 5.2	0.68
Cyp3a ^−/−	—	—	—	—	—	—
Human	1.61 ± 0.04	596 ± 18	369	24.5 ± 3.3	330 ± 11	13.5

—, no metabolite detected (detection limit <5 pmol/min/mg protein).