. Author manuscript; available in PMC: 2008 Sep 8.

Published in final edited form as: J Am Chem Soc. 2007 Apr 6;129(17):5760–5765. doi: 10.1021/ja069111+

Table 3.

Kinetic Isotope Effects for Solution and Enzymatic Reactions of pNPP and pNPS^a

Enzymatic Reactions ^b	Substrate	¹⁵(V/K)	¹⁸(V/K) _bridge	¹⁸(V/K)_nonbridge
wt AP³³	pNPP^2-	1.0003 (2)	1.0003 (4)	0.9982 (1)
R166S AP	pNPP^2-	1.0007 (1)	1.0091 (6)	0.9925 (11)
wt AP	pNPS^1-	1.0019 (4)	1.0084 (10)	0.9946 (4)
Uncatalyzed Reactions	Substrate	¹⁵k	¹⁸k_bridge	¹⁸k_nonbridge
At 95 °C⁵²	pNPP^2-	1.0028 (2)	1.0189 (5)	0.9994 (5)
At 85 °C⁵²	pNPS^1-	1.0026 (1)	1.0210 (10)	0.9951 (3)

Standard errors for the last decimal place(s) are in parenthesis. Data for the reaction of wt AP with pNPP^2- and for solution reactions are from previous work.⁵², ⁵⁴ Data for all other reactions were obtained for this work. KIEs for wt AP-catalyzed pNPP^2- hydrolysis are close to unity because the chemical step is not rate-determining.³⁵, ⁵²

Enzymatic reactions with pNPP^2- were conducted at 25 °C and with pNPS^1- were conducted at 35 °C (see Methods). Although differences in temperature can effect the observed KIEs, these effects are small and do not affect the conclusions drawn herein.⁶⁸, ⁷²