TABLE 1

Apparent kinetic parameters for the formation of 3MI metabolites by OM microsomes from WT, Cyp2a5-null, and Cyp2f2-null mice

Rates of metabolite formation were determined as described under Materials and Methods. Values presented are the means ± S.D. of data from three separate microsomal samples, each prepared from tissues pooled from five mice. Corresponding substrate-velocity curves are shown in supplemental material. The rates of HMI, I-3-C, and MOI formation were determined in the absence of added GSH. For HMI and GS-A2, the K_m and V_max values were estimated from relative rates determined in arbitrary units.

Metabolite	Strain	K_m	V_max	V_max/K_m
		μM	nmol · min⁻¹ · mg protein⁻¹	ml · min⁻¹ · mg⁻¹ ·
I-3-C	WT	7.32 ± 0.61	1.23 ± 0.11	0.17
	Cyp2a5-null	7.12 ± 0.79	0.29 ± 0.01^*	0.04
	Cyp2f2-null	6.90 ± 0.26	1.14 ± 0.16	0.17
MOI	WT	11.7 ± 0.5	1.41 ± 0.11	0.12
	Cyp2a5-null	31.5 ± 1.4^*	0.17 ± 0.01^*	0.01
	Cyp2f2-null	11.1 ± 1.1	1.40 ± 0.07	0.13
GS-A1	WT	5.49 ± 0.53	0.79 ± 0.03	0.14
	Cyp2a5-null	5.77 ± 0.37	0.73 ± 0.04	0.13
	Cyp2f2-null	10.3 ± 1.2^*	0.67 ± 0.09	0.07
			Arbitrary units (analyte peak area · internal standard peak area⁻¹ · min⁻¹ · mg protein⁻¹)
HMI	WT	6.41 ± 0.21	175 ± 2
	Cyp2a5-null	6.18 ± 0.41	171 ± 3
	Cyp2f2-null	6.50 ± 0.33	49 ± 2^*
GS-A2	WT	5.61 ± 0.91	194 ± 6
	Cyp2a5-null	5.56 ± 0.67	193 ± 6
	Cyp2f2-null	12.8 ± 1.7^*	77 ± 5^*

↵* P < 0.01, compared with WT mice (n = 3).