Table 2. Intrinsic Phosphodianion Binding Energies for Wild Type and Mutant Forms of OMPDC and the Effects of Mutations on the Dianion Binding Energy^a.

OMPDC	(kcat/Km)OMP/(kcat/Km)EOb	(ΔGPi∓)intc (kcal/mol)	(ΔGPi∓)intd (kcal/mol)
wild type	4.2 × 108	11.7
Q215A	2.3 × 107	10.0	1.7
Y217F	1.5 × 107	9.8	1.9
R235A	3.5 × 104	6.2	5.5
Q215A/Y217F	7.4 × 105	8.0	3.7
Q215A/R235A	3300	4.8	6.9
Y217F/R235A	410	3.6	8.1
Q215A/Y217F/R235A	12	1.5	10.2

^aFor OMPDC-catalyzed decarboxylation at 25 °C, pH 7.1 (30 mM MOPS), and ionic strength of 0.105 (NaCl).

^bRatio of second-order rate constants for OMPDC-catalyzed decarboxylation of OMP (Table 1) and EO (ref (28)).

^cRT ln((k_cat/K_m)_OMP/(k_cat/K_m)_EO).

^dThe difference between the 11.7 kcal/mol intrinsic phosphodianion binding energy for wild-type OMPDC and the respective mutant of OMPDC.