We have reported good linear correlation between the kinetic (activation free energy, ∆G ‡ ) and thermodynamic (reaction free energy, ∆G 0 ) barriers for the deprotonation of substrates DHAP and GAP by propionate ion from solvent, wild-type TIM, and the I170A, L230A and I170A/L230A variants. Figure shows large extensions of these linear free energy relationships (LFER) to include all 11 enzyme variants studied in this work. These LFER define strong linear correlations between the kinetic and thermodynamic reaction barriers, with slopes of b = 0.73 ± 0.03 (R 2 = 0.994) and b = 0.74 ± 0.02 (R 2 =0.995) for the deprotonation of DHAP and GAP, respectively. By comparison, Brønsted correlations that include only data for the enzymatic reactions give β = 0.66 ± 0.04 (R 2 = 0.983) and β = 0.70 ± 0.06 (R 2 = 0.972) for the deprotonation of DHAP and GAP, respectively. The small differences between the slopes determined when data for the non-enzymatic reaction is omitted or included in these fits is consistent with a similar transition state structure for nonenzymatic and TIM-catalyzed deprotonation of DHAP and GAP.