Inter domain interactions influence the substrate affinity and hydrolysis product specificity of xylanase from Streptomyces chartreusis L1105

Ke Xiong,Le Gao,Jia Yun Liu,Bao Guo Sun,Peng Gang Pei,Lei Deng,Zi Xiang Yan

doi:10.1186/s13213-020-01560-1

Ke Xiong, Le Gao + Show 5 more

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https://doi.org/10.1186/s13213-020-01560-1

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Abstract

PurposeThis study investigated the influence of inter-domain interactions on the substrate affinity and hydrolysis product specificity of xylanase.MethodsGenes encoding a GH10 endo-xylanase from Streptomyces chartreusis L1105 xynA and its truncated derivative were cloned and expressed in Escherichia coli. The catalytic activities of the enzyme (xynA) and the derivative xynADCBM, lacking the carbohydrate binding module (CBM), were assessed to evaluate the role of CBM in xynA.ResultsRecombinant xynA (44 kDa) was found to be optimally active on beechwood xylan at 65 °C with pH 7.7, while xynADCBM (34 kDa) exhibited optimal activity at 65 °C with pH 7.2. Additionally, xynA and xynADCBM were found to be highly thermostable at 40–60 °C, each retaining 80% of their original activity after 30 min. The xynADCBM without the CBM domain was highly efficient at hydrolyzing xylan to produce xylobiose (over 67%), which may be because the CBM domain facilitates substrate binding with xylanase. Meanwhile, the xylan hydrolysis efficiency of xynADCBM was higher than that of xynA.ConclusionThese findings showed that the CBM domain with non-catalytic activity has no significant effect on the characteristics of the enzyme at optimum pH and pH tolerance. It has also been suggested that the derivative xynADCBM without CBM components can promote hydrolysis of xylan to yield xylooligosaccharides, which has great potential economic benefits.

Highlights

Xylan is the main carbohydrate in hemicellulose, which constitutes 30–35% of the biomass of lignocellulose (Sousa et al 2016)
The core sequence of the xylanase gene was analyzed using NCBI BLAST, and the results showed that the gene sequence was highly homologous with these gene sequences in GenBank (Accession numbers HE971709.1, AF194024, and AB110643.1)
XynA and xynADCBM both retained 80% activity at pH 6.2–10.3 at 50 °C for 30 min. These findings showed that the carbohydrate binding module (CBM) domain with no catalytic activity had no significant effect on the characteristics of enzymes at the optimum pH or the range of tolerated pH values (Fig. 3c, d)

Summary

Introduction

Xylan is the main carbohydrate in hemicellulose, which constitutes 30–35% of the biomass of lignocellulose (Sousa et al 2016). Xylan is essential in the subsequent conversion steps that yield other value-added products from hemicellulosic materials (Petzold-Welcke et al 2014). These steps require a series of hydrolytic enzymes to complete saccharification. Xylanase plays an important role in xylan hydrolysis by catalyzing the hydrolysis of 1,4-D xylosidic linkages in xylan to yield short xylooligosaccharides (XOS), which have great potential economic benefits. Xylooligosaccharides are oligomers containing 2–7 xylose molecules linked by β (1–4) glycosidic bonds (Bian et al 2013), which are obtained by the degradation of xylans via chemical, physical, and enzymatic degradation process. Xylooligosaccharides have a variety of biological activities, such as promoting the growth of beneficial intestinal bacteria (Samanta et al 2015), accelerating the metabolism of

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