Identification and Characterization of a Novel, Cold-Adapted d-Xylobiose- and d-Xylose-Releasing Endo-β-1,4-xylanase from an Antarctic Soil Bacterium, Duganella sp. PAMC 27433.

Do Young Kim,Bon-Hwan Ku,Yung Mi Lee,Dong-Ha Shin,Jonghoon Kim,Kwang-Hee Son,Jong Suk Lee,Ho-Yong Park

doi:10.3390/biom11050680

Abstract

Endo-β-1,4-xylanase is a key enzyme in the degradation of β-1,4-d-xylan polysaccharides through hydrolysis. A glycoside hydrolase family 10 (GH10) endo-β-1,4-xylanase (XylR) from Duganella sp. PAMC 27433, an Antarctic soil bacterium, was identified and functionally characterized. The XylR gene (1122-bp) encoded an acidic protein containing a single catalytic GH10 domain that was 86% identical to that of an uncultured bacterium BLR13 endo-β-1,4-xylanase (ACN58881). The recombinant enzyme (rXylR: 42.0 kDa) showed the highest beechwood xylan-degrading activity at pH 5.5 and 40 °C, and displayed 12% of its maximum activity even at 4 °C. rXylR was not only almost completely inhibited by 5 mM N-bromosuccinimide or metal ions (each 1 mM) including Hg2+, Ca2+, or Cu2+ but also significantly suppressed by 1 mM Ni2+, Zn2+, or Fe2+. However, its enzyme activity was upregulated (>1.4-fold) in the presence of 0.5% Triton X-100 or Tween 80. The specific activities of rXylR toward beechwood xylan, birchwood xylan, oat spelts xylan, and p-nitrophenyl-β-d-cellobioside were 274.7, 103.2, 35.6, and 365.1 U/mg, respectively. Enzymatic hydrolysis of birchwood xylan and d-xylooligosaccharides yielded d-xylose and d-xylobiose as the end products. The results of the present study suggest that rXylR is a novel cold-adapted d-xylobiose- and d-xylose-releasing endo-β-1,4-xylanase.

Highlights

Endo-β-1,4-xylanase is a key enzyme in the degradation of β-1,4-D-xylan polysaccharides through hydrolysis
The biological recycling of such polysaccharides is primarily performed by various microorganisms including bacteria, yeasts, and filamentous fungi, which produce exo- and endo-type β-1,4-D-xylan-degrading glycoside hydrolases (GHs) [2]
We suggest that rXylR is a novel, cold-adapted glycoside hydrolase family 10 (GH10) endo-β-1,4-xylanase showing distinct biocatalytic activities and substrate specificities, different from the known GH10 functional homologs

Summary

Introduction

Endo-β-1,4-xylanase is a key enzyme in the degradation of β-1,4-D-xylan polysaccharides through hydrolysis. 1. Introduction β-1,4-D-xylan is a primary hemicellulosic polysaccharide in hardwood trees. Introduction β-1,4-D-xylan is a primary hemicellulosic polysaccharide in hardwood trees It is constituted of D-xylose molecules linked by β-1,4-D-xylosidic bonds in the backbone of the polysaccharide chains. These D-xylose-based hemicelluloses are often found in a specific form with different side-chain substitutions such as either acetyl, glucuronopyranosyl, α-L-arabinofuranosyl, 4-O-methyl-D-glucuronopyranosyl, feruloyl, p-coumaroyl groups, or in combination [1]. The biological recycling of such polysaccharides is primarily performed by various microorganisms including bacteria, yeasts, and filamentous fungi, which produce exo- and endo-type β-1,4-D-xylan-degrading glycoside hydrolases (GHs) [2]

Methods

Results

Conclusion