Table 1.

K_m and V_max values calculated from SULT1B1-WT and SULT1B1-L145V’s 1-naphthol, p-nitrophenol, 1-hydroxypyrene, and PAPS variable concentration plots.

	1-naphthola		p-nitrophenola		1-hydroxypyrenea		PAPSd
		Km(µM)	Vmax (pmol/(min*µg))	Km(µM)	Vmax (pmol/(min*µg))	Ks(µM)b	Vmax (pmol/(min*µg))	Km(µM)	Vmax (pmol/(min*µg))
SULT1B1-WT	1.4±0.6	10.1±1.9	7.2±0.7	14.4±0.5	33.5±10.8	N/Ac	2.2±0.4	1.3±0.1
SULT1B1-L145Ve	1.3±0.4	9.3±1.0	11.3±2.7	6.8±0.7*	7.7±0.3	N/Ac	1.6±0.4	0.9±0.1

^aSubstrate apparent values were measured using 15 µM PAPS. All errors represent SEM.

^bA K_m estimate was not possible because of the sigmoidal curve.Instead, K_s(the nth root of K’,composed of “interaction factors” was calculated).

^cThe sigmoidal nature of the curve and potent substrate inhibition do not allow accurate estimation of the V_max.

^dPAPS apparent values were measured using 6.25 µM 1-hydroxypyrene.All errors represent SEM.

^eAstrisks indicate significant differences from the WT(*,P < 0.01)