Understanding the roles enthalpy and entropy play in enzymatic reactions requires intimate knowledge of the microscopic details underlying these reactions. Due to difficulties in obtaining atomistic levels of detail in enzymatic reactions, making use of computer simulations provides an optimal route to study the details of the activation enthalpy-entropy balance of such systems. In this study, we employ semi-empirical EVB/MD free energy calculations to study the chorismate mutase reaction in PchB and BsCM. EVB was chosen due to its ability to accurately calculate free energies while being less computationally intensive than ab initio QM/MM methods. Furthermore, EVB can be combined with an Arrhenius plot to extract thermodynamic activation enthalpies and entropies. In our work, simulations are performed at 6 evenly spaced temperatures ranging from 288K-313K, allowing for calculation of the thermodynamic activation parameters from an Arrhenius plot. 2