Biochemical characterization, substrate and stereoselectivity of an outer surface putative α/β hydrolase from the pathogenic Leptospira

Abstract

The genome of pathogenic leptospira encodes a plethora of outer surface and secretory proteins. The outer surface or secreted α/β hydrolases in a few pathogenic organisms are crucial virulent factors. They hydrolyze host immune factors and pathogen's immune-activating ligands, which help pathogens to evade the host's innate immunity. In this study, we report biochemical characterizations, substrate and stereoselectivity of one of the leptospiral outer surface putative α/β hydrolases, IQB77_09235 (LABH). Purified LABH displayed better kinetic parameters towards small water-soluble esters such as p-nitrophenyl acetate and p-nitrophenyl butyrate. The LABH exhibited moderate thermostability and displayed a pH optimum of 8.5. Remarkably, a phylogenetic study suggested that LABH does not cluster with other characterized bacterial esterases or lipases. Protein structural modeling revealed that some structural features are closely associated with Staphylococcus hycus lipase (SAH), a triacylglycerol hydrolase. The hydrolytic activity of the protein was found to be inhibited by a lipase inhibitor, orlistat. Biocatalytic application of the protein in the kinetic resolution of racemic 1-phenylethyl acetate reveals excellent enantioselectivity (E > 500) in the production of (R)-1-phenylethanol, a valuable chiral synthon in several industries. To our knowledge, this is the first detailed characterization of outer surface α/β hydrolases from leptospiral spp.