PcMulGH9, a novel glycoside hydrolase family 9 (GH9) from Paenibacillus curdlanolyticus B-6, was successfully expressed in Escherichia coli. It is composed of a catalytic domain of GH9, two domains of carbohydrate-binding module family 3 (CBM3) and two domains of fibronectin type 3 (Fn3). The PcMulGH9 enzyme showed broad activity towards the β-1,4 glycosidic linkages of cellulose, mannan and xylan, including cellulose and xylan contained in lignocellulosic biomass, which is rarely found in GH9. The enzyme hydrolysed substrates with bifunctional endo-/exotypes cellulase, mannanase and xylanase activities, but predominantly exhibited exo-activities. This enzyme released cellobiose as a major product from cellohexaose, while mannotriose and xylotriose were major hydrolysis products from mannohexaose and xylohexaose, respectively. Moreover, PcMulGH9 could hydrolyse untreated corn hull and rice straw into xylo- and cello-oligosaccharides. Enzyme kinetics, site-directed mutagenesis and molecular docking revealed that Met394, located at the binding subsite + 2, was involved in broad substrate specificity of PcMulGH9 enzyme. This study offers new knowledge of the multifunctional cellulase/mannanase/xylanase in GH9. The PcMulGH9 enzyme showed a novel function of GH9, which increases its potential for saccharification of lignocellulosic biomass into value-added products, especially oligosaccharides.

中文翻译：

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一种新的多功能GH9酶，来自解脂巴氏芽孢杆菌B-6，具有纤维素酶，甘露聚糖酶和木聚糖酶活性的内/外功能。

PcMulGH9是一种新的糖苷水解酶家族9（GH9），它来自于Padenbacillus curdlanolyticus B-6，已在大肠杆菌中成功表达。它由GH9的催化结构域，碳水化合物结合模块家族3的两个结构域（CBM3）和纤连蛋白3型的两个结构域（Fn3）组成。PcMulGH9酶对纤维素，甘露聚糖和木聚糖的β-1,4糖苷键具有广泛的活性，包括木质纤维素生物质中所含的纤维素和木聚糖，这在GH9中很少见。该酶水解具有双功能内切/外切型纤维素酶，甘露聚糖酶和木聚糖酶活性的底物，但主要表现出外切活性。该酶释放纤维二糖作为纤维六糖的主要产物，而甘露三糖和木三糖分别是甘露六糖和木六糖的主要水解产物。此外，PcMulGH9可以将未经处理的玉米壳和稻草水解为木糖和纤维寡糖。酶动力学，定点诱变和分子对接表明，位于结合亚位点+2的Met394与PcMulGH9酶的广泛底物特异性有关。这项研究提供了GH9中多功能纤维素酶/甘露聚糖酶/木聚糖酶的新知识。PcMulGH9酶显示出GH9的新功能，增加了其将木质纤维素生物质糖化成增值产品（尤其是低聚糖）的潜力。这项研究提供了GH9中多功能纤维素酶/甘露聚糖酶/木聚糖酶的新知识。PcMulGH9酶显示出GH9的新功能，增加了其将木质纤维素生物质糖化成增值产品（尤其是低聚糖）的潜力。这项研究提供了GH9中多功能纤维素酶/甘露聚糖酶/木聚糖酶的新知识。PcMulGH9酶显示出GH9的新功能，增加了其将木质纤维素生物质糖化成增值产品（尤其是低聚糖）的潜力。