Gene Cloning, Expression and Characterization of a Novel Xylanase from the Marine Bacterium, Glaciecola mesophila KMM241

Bing Guo,Xiu-Lan Chen,Xi-Ying Zhang,Sheng Dong,Ping-Yi Li,Wei-Xin Zhang,Xiao-Yan Song,Yu-Zhong Zhang,Bai-Cheng Zhou,Hui-Lin Zhao,Yong-Sheng Yue,Cai-Yun Sun

doi:10.3390/md11041173

Abstract

Marine xylanases are rather less studied compared to terrestrial xylanases. In this study, a new xylanase gene, xynB, was cloned from the marine bacterium, Glaciecola mesophila KMM241, and expressed in Escherichia coli. xynB encodes a multi-domain xylanase XynB of glycoside hydrolase (GH) family 8. The recombinant XynB comprises an N-terminal domain (NTD) with unknown function and a catalytic domain, which is structurally novel among the characterized xylanases of GH family 8. XynB has the highest identity (38%) to rXyn8 among the characterized xylanases. The recombinant XynB showed maximal activity at pH 6–7 and 35 °C. It is thermolabile and salt-tolerant. XynB is an endo-xylanase that demands at least five sugar moieties for effective cleavage and to hydrolyze xylohexaose and xylopentaose into xylotetraose, xylotriose and xylobiose. NTD was expressed in Escherichia coli to analyze its function. The recombinant NTD exhibited a high binding ability to insoluble xylan and avicel and little binding ability to chitosan and chitin. Since the NTD shows no obvious homology to any known carbohydrate-binding module (CBM) sequence in public databases, XynB may contain a new type of CBM.

Highlights

Xylan, which together with lignin and cellulose constitutes the major components of plant cell walls, is the most abundant hemicellulose in nature and represents an important type of renewable resource [1]
2739 bp, including an ATG start codon and a TAA stop codon. It encodes a protein of 912 amino acid residues with a calculated Mr of 100,502 Da, which was predicted to be a glycoside hydrolase (GH) family 8 xylanase
Gene xynB cloned from the marine bacterium, Glaciecola mesophila KMM241, encodes a multi-domain xylanase XynB of GH family 8, which has a low identity (38%) to the characterized xylanases

Summary

Introduction

Xylan, which together with lignin and cellulose constitutes the major components of plant cell walls, is the most abundant hemicellulose in nature and represents an important type of renewable resource [1]. Complete biodegradation of xylan requires synergy of a variety of xylanolytic enzymes. According to the amino acid sequences of catalytic domains, enzymes with xylanase activity can be categorized into glycoside hydrolase (GH) families 5, 7, 8, 10, 11, 16, 26, 43, 52 and 62. Only those sequences classified into families 5, 7, 8, 10, 11 and 43 contain truly distinct catalytic domains with a demonstrated endo-1,4-β-xylanase activity. Those enzymes classified into family 26 are endo-1,3-β-xylanases [2]

Methods

Results

Discussion

Conclusion