Background: A recombinant carboxylesterase, cloned from Pseudomonas putidaand designated as rPPE, is capable of catalyzing the bioresolution of racemic 2-acetoxy-2-(2-chlorophenyl)acetate (rac-AcO-CPA) with excellent enantioselectivity.Rational design of the enzyme shows that the variant W187H could increase the activity by ~100-fold comparedto the wild type (WT).As the crystal structures of Apo-rPPE and rPPE in complex with (S)-AcO-CPA were resolved recently, we can carry out molecular dynamic simulations to gain more insights into the molecular mechanism regarding ligand recognition and catalytic efficiency of the carboxylesterase rPPE.