A novel esterase from a soil metagenomic library displaying a broad substrate range

Jian Yao,Shaocheng Yin,Lun Gui

doi:10.1186/s13568-021-01198-5

Abstract

A novel esterase gene was isolated from a soil metagenomic library. The gene encoded a protein of 520 amino acids which contained a 21 aa signal peptide. Primary structure analysis of the protein sequence revealed that it contained a conserved active site motif (SxSxG) and a structural motif (CS-D-HC). Then the esterase gene was cloned and expressed in Escherichia coli BL21(DE3). SDS-PAGE analysis of the purified esterase showed that it was expressed in a highly soluble form and its molecular mass was estimated to be 55 kDa. Characterization of the esterase revealed that it exhibited high activity toward p-nitrophenyl esters with short acyl chains and especially p-nitrophenyl acetate, suggesting that it was a typical carboxylesterase rather than a lipase. With p-nitrophenyl acetate as substrate, the enzyme showed its optimal activity at pH 7.0 and 30 °C, and it was stable at a broad pH range from 4.5 to 10.0 and temperature not higher than 50 °C. Furthermore, the enzyme showed different substrate specificity from known esterase, it was not only hydrolyzing against p-nitrophenyl esters, but also hydrolyzing all hydroxybenzoic esters and hydroxycinnamic ester assayed. As it was an enzyme active on a broad range of phenolic esters, simultaneously possessing feruloyl esterase, chlorogenate esterase and tannase activities, it could serve as a valuable candidate for applications in biotechnology.

Highlights

Plant cell wall polysaccharides, the major reservoir of fixed carbon in nature, had been divided into three main groups: cellulose, hemicellulose and lignin (Kosugi et al 2001). In addition to these main groups, phenolic compounds were thought to be playing a key role in structure of the plant cell wall as they covalently cross-linked plant cell wall polysaccharides to each other by ester bonds (Ishii 1997; Nieter et al 2015)
Phenolic compounds, ubiquitous in plants were essential part of human diet, as they accounted for all most one-third of dietary phenols (Haminiuk et al 2012; Esteban-Torres et al 2015), which could be found in apple, artichoke, eggplant, grape, pear, potato and grape
It was interesting to find that Tan410 could hydrolyze methyl ferulate, methyl p-coumarate and methyl caffeate, but not methyl sinapate, indicating that Tan410 showed feruloyl esterase activity and concluding that Tan410 was a type B feruloyl esterase

Summary

Introduction

The major reservoir of fixed carbon in nature, had been divided into three main groups: cellulose, hemicellulose and lignin (Kosugi et al 2001) In addition to these main groups, phenolic compounds were thought to be playing a key role in structure of the plant cell wall as they covalently cross-linked plant cell wall polysaccharides to each other by ester bonds (Ishii 1997; Nieter et al 2015). Phenolic compounds were reported to protect plants from oxidative stress, UV radiation, invasion and infection (Jaleel et al 2009) These phenolic compounds influenced the rigidity and mechanical properties of the cell wall and played a role in plant defense (Nieter et al 2015; Cosgrove 2001).

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Conclusion