A novel fungal GH30 xylanase with xylobiohydrolase auxiliary activity
A novel fungal GH30 xylanase with xylobiohydrolase auxiliary activity
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DOI：
10.1186/s13068-019-1455-2
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发表时间：
2019-05-11
影响因子：
6.3
通讯作者：
Topakas, Evangelos
中科院分区：
文献类型：
--
作者：
Katsimpouras, Constantinos;Dedes, Grigorios;Topakas, Evangelos
半纤维素的主要代表是木聚糖，通常是修饰的-1,4-连接的d-木糖聚合物，由木聚糖酶水解。木聚糖的高效利用和完全水解需要了解木聚糖降解酶的作用方式。糖苷水解酶家族30 （GH30）木聚糖酶是一类研究较少的此类酶，真菌和细菌GH30木聚糖酶在底物识别方面存在差异。除了利用木质纤维素生物质作为生物能源外，由于它们的底物特异性，这些酶还可以用于定制生产益生元低聚木糖（XOS）。结果通过在毕赤酵母中表达嗜热热霉菌（Thermothelomyces thermophila, Sporotrichum thermophila）中推测的GH30_7木聚糖酶，产生并分离出一种具有独特催化性能的新型木聚糖酶。这种新酶被命名为TtXyn30A，表现出类似于细菌GH30木聚糖酶的内切模式，需要4- o-甲基-d-葡萄糖醛酸（MeGlcA）修饰，与大多数特征的真菌木聚糖酶形成对比。然而，TtXyn30A也表现出外显作用的催化行为，通过从XOS的非还原端释放双糖木糖糖。山毛榉木葡萄糖醛酸酶解产物为MeGlcA取代XOS和木糖糖。经过较长时间的培养，TtXyn30A主要的糖醛酸裂解产物是醛三醛酸和醛四醛酸，这表明TtXyn30A也能裂解木聚糖和糖醛酸的线性部分。结论本研究报道了一种新型真菌GH30木聚糖酶的异种生产和生化特性，该酶具有内、外木聚糖酶活性。迄今为止，考虑到其新颖的催化特性，TtXyn30A与大多数表征的真菌和细菌GH30木聚糖酶存在差异。发现木质素生物水解酶的作用模式为真菌酶系统提供了新的见解，用于木质纤维素生物质的利用。重组木聚糖酶可用于葡萄糖醛酸氧化酶生产X2和UXOS，作为具有多种健康益处的益生元。
BackgroundThe main representatives of hemicellulose are xylans, usually decorated -1,4-linked d-xylose polymers, which are hydrolyzed by xylanases. The efficient utilization and complete hydrolysis of xylans necessitate the understanding of the mode of action of xylan degrading enzymes. The glycoside hydrolase family 30 (GH30) xylanases comprise a less studied group of such enzymes, and differences regarding the substrate recognition have been reported between fungal and bacterial GH30 xylanases. Besides their role in the utilization of lignocellulosic biomass for bioenergy, such enzymes could be used for the tailored production of prebiotic xylooligosaccharides (XOS) due to their substrate specificity.ResultsThe expression of a putative GH30_7 xylanase from the fungus Thermothelomyces thermophila (synonyms Myceliophthora thermophila, Sporotrichum thermophile) in Pichia pastoris resulted in the production and isolation of a novel xylanase with unique catalytic properties. The novel enzyme designated TtXyn30A, exhibited an endo- mode of action similar to that of bacterial GH30 xylanases that require 4-O-methyl-d-glucuronic acid (MeGlcA) decorations, in contrast to most characterized fungal ones. However, TtXyn30A also exhibited an exo-acting catalytic behavior by releasing the disaccharide xylobiose from the non-reducing end of XOS. The hydrolysis products from beechwood glucuronoxylan were MeGlcA substituted XOS, and xylobiose. The major uronic XOS (UXOS) were the aldotriuronic and aldotetrauronic acid after longer incubation indicating the ability of TtXyn30A to cleave linear parts of xylan and UXOS as well.ConclusionsHereby, we reported the heterologous production and biochemical characterization of a novel fungal GH30 xylanase exhibiting endo- and exo-xylanase activity. To date, considering its novel catalytic properties, TtXyn30A shows differences with most characterized fungal and bacterial GH30 xylanases. The discovered xylobiohydrolase mode of action offers new insights into fungal enzymatic systems that are employed for the utilization of lignocellulosic biomass. The recombinant xylanase could be used for the production of X2 and UXOS from glucuronoxylan, which in turn would be utilized as prebiotics carrying manifold health benefits.