Table 2

Selectivity of probe substrate catalysis by the five major human hepatic CYPs

Probe Reaction	Substrate Concentration	V
Probe Reaction	Substrate Concentration	CYP1A2	CYP2C9	CYP2C19	CYP2D6	CYP3A4
		pmol · min⁻¹ · pmol⁻¹
EROD	3	0.40	0.01	0.05	ND	ND
	1	0.30	ND	ND	ND	ND
NaproxenO-demethylation	2000	3.90	6.80	4.80	0.08	ND
	300	3.46	2.36	0.87	ND	ND
DiazepamN-demethylation	100	ND	0.03	2.61	ND	1.43
	20	ND	0.02	1.47	ND	0.48
DextromethorphanO-demethylation	30	ND	0.67	1.81	4.00	0.04
	3	ND	0.03	0.21	2.90	ND
ErythromycinN-demethylation	300	ND	0.09	0.23	0.31	2.59
	40	ND	ND	0.03	0.03	1.62

ND not detectable (< 0.005 min⁻¹).
Enzyme sources were E. coli membranes expressing CYP1A2, CYP2C9, CYP2C19 (single plasmid), CYP2D6, and CYP3A4 as described inMaterials and Methods.