Biochemical characterization of an enantioselective esterase from Brevundimonas sp. LY-2

Jing Zhang,Jingang Yin,Die Yu,Hao Zhang,Xing Huang,Mengjun Zhao

doi:10.1186/s12934-017-0727-4

Abstract

BackgroundLactofen, a member of the diphenylether herbicides, has high activity and is commonly used to control broadleaf weeds. As a post-emergent herbicide, it is directly released to the environment, and easily caused the pollution. This herbicide is degraded in soil mainly by microbial activity, but the functional enzyme involved in the biodegradation of lactofen is still not clear now.ResultsA novel esterase gene lacH, involved in the degradation of lactofen, was cloned from the strain Brevundimonas sp. LY-2. The gene contained an open reading frame of 921 bp, and a putative signal peptide at the N-terminal was identified with the most likely cleavage site between Ala 28 and Ala 29. The encoded protein, LacH, could catalyze the hydrolysis of lactofen to form acifluorfen. Phylogenetic analysis showed that LacH belong to family V of bacterial lipolytic enzymes. Biochemical characterization analysis showed that LacH was a neutral esterase with an optimal pH of 7.0 and an optimal temperature of 40 °C toward lactofen. Besides, the activity of LacH was strongly inhibited by Hg2+ and Zn2+. LacH preferred short chain p-nitrophenyl esters (C2–C6), exhibited maximum activity toward p-nitrophenyl acetate. Furthermore, the enantioselectivity of LacH during lactofen hydrolysis was also studied, and the results show that R-(−)-lactofen was degraded faster than S-(+)-lactofen, indicating the occurrence of enantioselectivity in the enzymatic reaction.ConclusionsOur studies characterized a novel esterase involved in the biodegradation of diphenylether herbicide lactofen. The esterase showed enantioselectivity during lactofen degradation, which revealed the occurrence of enzyme-mediated enantioselective degradation of chiral herbicides.

Highlights

Lactofen, a member of the diphenylether herbicides, has high activity and is commonly used to control broadleaf weeds
We have found that the degradation process of lactofen by LY-2 is enantioselective, with R-(−)-lactofen being degraded faster than the S-(+)-enantiomer, which implies that the enzyme involved in lactofen degradation probably has the enantioselectivity between the different enantiomers
Cloning and sequence analysis of the esterase gene The total DNA was extracted from strain Brevundimonas sp

Summary

Introduction

A member of the diphenylether herbicides, has high activity and is commonly used to control broadleaf weeds. As a post-emergent herbicide, it is directly released to the environment, and caused the pollution This herbicide is degraded in soil mainly by microbial activity, but the functional enzyme involved in the biodegradation of lactofen is still not clear now. Enantiomers of a chiral compound exhibit identical physical and chemical properties [2]. Their toxicities, biological activities and environmental fates vary because biological processes usually show high enantioselectivity [3, 4]. When one enantiomer is preferentially degraded, the enantiomeric ratio [ER, the ratio of the concentration of (+)-enantiomers to (−)-enantiomers] deviates from the original value [2, 8] The occurrence of such selective degradation involves the mediation of bacteria, enzymes, or other biological entities

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Conclusion