TABLE 2. Rates of H₂O₂ Generation by Recombinant Human P450 Enzymes (nmol of H₂O₂/min/nmol P450)^a.

CYP enzyme	Lot no.	Expressed without cytochrome b5	Expressed with cytochrome b5	With cytochrome b5 addedb	P450:OR ratioc
CYP2C9	29,127		0.21		1.91
CYP2C9	77,477		0.26		2.45
CYP2C9	19,924		0.22 ± 0.10		6.22
CYP2E1	87,639		5.24 ± 0.22		0.27
CYP2E1	44,748		5.16 ± 0.28		0.52
CYP2E1	29,047		5.26 ± 0.31		1.1
CYP3A4	27,001		4.92 ± 0.21		0.2
CYP3A4	10,738	5.29 ± 0.31		4.66 ± 0.28	2.53
CYP3A4	32,017	5.77 ± 0.15		5.06 ± 0.14	4.14

^aH₂O₂ generation by the recombinant P450 enzymes was determined using the AR/HRP assay as described in the Materials and Methods section.

^bFor every pmol of cytochrome P450/assay, 5 pmol of pure cytochrome b5 was added as described in the Materials and Methods section.

^cThe ratio P450:OR was calculated as described in the Materials and Methods section.