TABLE 2

Enzyme kinetic parameters of the formation of the pharmacologically active metabolite of clopidogrel from 2-oxo-clopidogrel

The assays were performed by using the microsomes baculovirus/insect cells expressing human cytochrome P450 (Supersomes). K_m and V_max values were expressed as mean ± S.E. of parameter estimate. CL_int and f_mP450 (P450 contribution ratio) values were scaled to eqs. 2 and 3 under Materials and Methods to determine contribution.

	Incubation Time	K_m	V_max	V_max/K_m	Enzyme Abundances*	CL_{int, expressed P450}	f_mP450 %
	min	μM	pmol/pmol P450/min	μl/pmol P450/min	pmol P450/mg protein	μl/mg protein/min
CYP2B6	15	1.62 ± 0.08	2.48 ± 0.03	1.53	11	16.8	32.9
CYP2C9	30	18.1 ± 3.8	0.855 ± 0.084	0.0472	73	3.45	6.76
CYP2C19	15	12.1 ± 2.2	9.06 ± 0.68	0.749	14	10.5	20.6
CYP3A4	15	27.8 ± 4.2	3.63 ± 0.29	0.131	155	20.3	39.8

↵* The abundances of CYP3A4, CYP2B6, CYP2C19, and CYP2C9 were obtained from the reported data in Rowland Yeo et al. (2004).