TABLE 1

Kinetic parameters of heterologously expressed human CYP2A13 and CYP2A6 in NNK α-hydroxylation

For CYP2A6 wild-type (WT), the values are the average of duplicate experiments with less than 15% variation.

Enzyme	Keto Aldehyde					Keto Alcohol
Enzyme		K_m	V_max	K_cat (V_max/K_m)	K_m	V_max	K_cat (V_max/K_m)
	μM	nmol/min/nmol		μM	nmol/min/nmol
CYP2A13 WT	14.0 ± 1.55	9.04 ± 1.77	0.646	12.1 ± 0.24	2.23 ± 0.53	0.185
CYP2A13 mutants
Ala¹¹⁷Val	18.5 ± 2.80	1.89 ± 0.37^*	0.102	11.0 ± 1.06	3.29 ± 0.81	0.300
His¹⁶⁴Gly	8.98 ± 2.45	8.89 ± 2.13	0.990	12.9 ± 2.02	3.24 ± 1.25	0.252
Ser²⁰⁸Ile	2.0 ± 6.81^**	3.59 ± 0.82^*	0.069	59.7 ± 17.9^**	1.01 ± 0.04	0.017
His³⁷²Arg	260 ± 22.2^**	1.23 ± 0.60^*	0.005	N.D.	N.D.	N.D.
Pro⁴⁶⁵Ser	44.6 ± 4.89^**	7.12 ± 2.13	0.160	48.1 ± 13.0^**	1.80 ± 0.41	0.037
CYP2A6 WT	328^**	1.03^*	0.003	N.D.	N.D.	N.D.

N.D., nondetectable.

^*P < 0.05, ^** P < 0.01, compared with CYP2A13 WT. The values are mean ± S.D. of three experiments.