. Author manuscript; available in PMC: 2010 Nov 3.

Published in final edited form as: Biochemistry. 2009 Nov 3;48(43):10416–10422. doi: 10.1021/bi901161b

Table 2.

Kinetic constants of HuPON1, G2E6, G3C9, and variants with VX and VR

	VX	VR

Enzyme	k_cat/K_M (M⁻¹ s⁻¹)^*	k_cat (s⁻¹)	K_M (mM)	k_cat/K_M (M⁻¹ s⁻¹)
HuPON1	550 ± 130	0.1 ± 0.04	0.20 ± 0.04	700 ± 180
H115W	2170 ± 320	----	----	---
S193A	300 ± 30	0.09 ± 0.02	0.20 ± 0.04	470 ± 30
S193G	450 ± 40	0.1 ± 0.04	0.20 ± 0.01	520 ± 80
R214Q	280 ± 70	0.06 ± 0.01	0.20 ± 0.07	300 ± 70
S193A/R214Q	280 ± 20	0.08 ± 0.008	0.30 ± 0.07	280 ± 20

G2E6	22 ± 0.3	ND	ND	18^*
H115W	85 ± 0.5	ND	ND	8.3^*
S193A	28 ± 0.7	ND	ND	23^*
R214Q	18 ± 0.03	ND	ND	13^*

G3C9	10 ± 0.7	ND	ND	20 ± 2*

Values are shown ± standard deviation. Where no deviation is indicated, the error was <1% of the value.

At the maximum regulated concentration of nerve agent, no evidence of saturation was detected indicating that K_M>>[S] (1.4 mM for VX and VR). The Michaelis-Menten equation was thus reduced to v₀ = k_cat[E][S]/K_M and used to calculate the values shown. ND = Not Determined