We performed MD simulation of the WT complex of chorismate mutase with substrate for Michaelis Complex (MC) and Transition State Analog (TSA) to study the effect of local electric field produced by native enzyme on the stability of the reactant and transition state. Though the active site of the enzyme is surrounded by many charge residues such as R7, E78, R90, Y108, K60 and R63, but the reactant shows significant degree of flexibility during the simulations. Figure shows three representative snapshots from the MD simulations of MC at different time scale. It is evident from the figure that during simulation substrate loses several interactions with key residues such as R7 and Y108 which can be anticipated by the increasing distances of these residues with the substrate continuously with simulation time. To further quantify the effect of the charged residue on the reactant we calculated the total change in binding enthalpy using MMPBSA method. The calculation shows ΔHbinding as -31.0 kcal/mol which is mainly dominated by strong and favorable interactions by R7, R90, K60 and R63.