Different Structural Origins of the Enantioselectivity of Haloalkane Dehalogenases toward Linear beta-Haloalkanes: Open-Solvated versus Occluded-Desolvated Active Sites

摘要

The enzymatic enantiodiscrimination of linear beta-haloalkanes is difficult because the simple structures of the substrates prevent directional interactions. Herein we describe two distinct molecular mechanisms for the enantiodiscrimination of the beta-haloalkane 2-bromopentane by haloalkane dehalogenases. Highly enantioselective DbjA has an open, solvent-accessible active site, whereas the engineered enzyme DhaA31 has an occluded and less solvated cavity but shows similar enantioselectivity. The enantioselectivity of DhaA31 arises from steric hindrance imposed by two specific substitutions rather than hydration as in DbjA.