TABLE 3

Enzyme kinetic parameters for NADPH-dependent metabolism of tazarotenic acid to tazarotenic acid sulfoxide and hydroxytazarotenic acid (95% confidence interval shown in parentheses)

	CYP26A1		CYP26B1
Metabolite	K_m	Cl_int	K_m	Cl_int	k_cat_,B1k_cat,_A1
	μM	ml/min per nanomole	μM	ml/min per nanomole
TA-Sulfoxide	0.24 (0.18–0.27)	1.03 (0.87–1.18)	1.01 (0.85–1.18)	0.38 (0.34–0.44)	1.60 (1.52–1.68)
Hydroxy-TA^{^a}	0.39 (0.31–0.42)	4.01 (3.52–4.48)	0.56 (0.42–0.63)	3.67 (3.22–4.14)	1.32 (1.27–1.37)

↵^a Metabolite standard not available; concentrations derived from tazarotenic acid sulfoxide standard curve.