L-2-Haloacid dehalogenase (L-DEX YL) is a member of a family of enzymes that decontaminate a variety of environmental pollutants such as L-2-chloropropionate (L-2-CPA). This enzyme specifically catalyzes the hydrolytic dehalogenation of L-2-haloacid to produce D-2-hydroxy acid, and does not catalyze that of D-2-haloacid. Here, using the quantum-mechanical/molecular-mechanical and the fragment molecular orbital calculations, the enzymatic reaction of L-DEX YL to D-2-CPA was compared with that to L-2-CPA. As a result, Tyrl 2, Leu45 and Phe60 were predicted to affect the enantioselectivity. We then performed the site-directed-mutagenesis experiments and the activity measurement of these mutants, thus finding that the F60Y mutant had the enzymatic activity with D-2-CPA. (C) 2015 Elsevier B.V. All rights reserved.