TABLE 3

Kinetic parameters obtained for metabolite formation in P450s

P450 Enzyme	Relative Enzyme Abundance^{^a}	V_max	K_m	V_max/K_m	CL_int	Enzyme Contribution
	pmol P450/mg protein	pmol/min per pmol P450	µM		µl/mg protein per min	%
Formation of Met1 from CINPA1
CYP3A4	93	83.22	12.74	6.53	607.49	96.28
CYP2D6	12.6	20.43	261.40	0.08	0.98	0.16
CYP2C19	11	13.09	21.06	0.62	6.84	1.08
CYP2C9	61	3.92	32.63	0.12	7.33	1.16
CYP2B6	16	22.50	80.58	0.28	4.47	0.71
CYP1A2	39	4.17	41.89	0.10	3.88	0.61
Formation of Met2 from Met1
CYP3A4	93	—	—	—	—	—
CYP2D6	12.6	89.67	119.20	0.752	9.48	94.60
CYP2C19	11	11.98	745.90	0.016	0.18	1.76
CYP2C9	61	1.41	303.60	0.005	0.28	2.84
CYP2B6	16	—	—	—	—	—
CYP1A2	39	0.52	250.90	0.002	0.08	0.80

Kinetic parameters calculated for formation of Met1 from CINPA1 were estimated by fitting the velocity versus CINPA1 concentration curve for each enzyme to the Hill equation (curves represented in Supplemental Fig. 4A, as obtained from triplicate reaction wells). Kinetic parameters calculated for formation of Met2 from Met1 were estimated by fitting the velocity versus concentration curve in each enzyme, with Met1 as substrate, to the Hill equation (curves represented in Supplemental Fig. 4B, as obtained from triplicate reaction wells). Dashes indicate that the data for Met1 metabolism in CYP3A4 and CYP2B6 did not fit to the Hill equation and hence V_max and K_m could not be obtained (flagged as ambiguous by GraphPad Prism software).
↵^a The enzyme abundance of various P450s in HLMs was obtained from data reported by Achour et al. (2014) and is a meta-analysis based combination of multiple studies using numerous microsomal donors.