Arrhenius plots for the chorismate mutase enzymes, we first looked at thermodynamic behavior at 298 K. The calculated average reaction free energy profile along the reaction coordinate f or each enzyme (Figure ) yielded free energy barriers of ∆G ‡ = 15.8 kcal mol -1 for BsCM and ∆G ‡ = 18.3 kcal mol -1 for PchB, which show substantial catalysis compared to the uncatalyzed reference reaction activation barrier of ∆G ‡ = 24.4 kcal mol -1 . Activation free energies for both enzymatic reactions are also in good agreement with experimental values for the respective enzymes. To obtain thermodynamic activation parameters from an Arrhenius plot (Figure ), EVB/MD calculations were performed at the same 6 temperatures used for the reference reaction, using the same  and H12 values obtained from fitting the reference reaction to activation and reaction free energies of the uncatalyzed reaction obtained from experiment and DFT. From these simulations, we fitted ∆G ‡ /T vs. 1/T using linear regression, which yielded values of ∆H ‡ = 12.9 kcal mol -1 and T∆S ‡ = -2.9 kcal mol -1 for BsCM at 298 K. The same analysis for PchB yielded values of ∆H ‡ = 14.0 kcal mol -1 and T∆S ‡ = -4.3 kcal mol -1 at 298K. The values predicted using the Arrhenius plot approach for both enzymes are thus in very reasonable agreement with experimental values of ∆H ‡ = 12.7 kcal mol-1 and T∆S ‡ = -2.7 kcal mol -1 for BsCM at 298 K, and ∆H ‡ = 15.9 kcal mol -1 and T∆S ‡ = -3.6 kcal mol -1 for PchB at 298 K.