Cloning of the gene encoding endo-1, 4-β-mannosidase from Bacillus subtilis HB002 and expression in Pichia pastoris
首发时间:2012-11-19
Abstract:Endo-1, 4-β-mannosidase (E.C. 3.2.1.78), which is also called mannanase, catalyzes the random hydrolysis of β-1, 4-mannosidic linkages in the main chain of mannan and its heteropolysaccharides. Therefore, mannanases are widely applied not only in researches, but also in industries. Mannanases can be produced by various organisms, including bacteria, fungi, plants, and as well as animals. Bacillus subtilis is a major source of this enzyme. A gene from Bacillus subtilis HB002 coding an endo-1, 4-β-mannosidase belonging to glycoside hydrolyase family 26 (GH26), was first cloned from the genome with shot-gun method and the enzyme was heterogenously expressed in Pichia pastoris GS115, driven by a mutant of AOX1 promoter, the d1+2x201 AOX1 and the MF4I signal peptide. The expression of this enzyme was confirmed by SDS-PAGE and plate assay. The molecular weight of the recombinant protein is about 42 kDa. The expression of target protein is up to 0.25mg/mL and the enzyme activity is about 222 U/mL. According to the analysis of enzyme characteristics, the optimal pH is between pH5.6-7.0 and the optimal temperature is 55 C when locust bean gum is used as substrate. This enzyme is fairly stable at various pH and temperature. Accordingly, it is still stable at pH5.0 to 7.0 after incubation at room temperature for 5h. The enzyme remains about 95% activity after 10h incubated at 50 C. In addition, it shows strong substrate specificity to galactomannans and konjac powder. The enzyme activity is strongly inhibited by Co2+ and Mn2+, but it is not sensitive to other ions. Analysis of hydrolytic products by thin layer chromatography (TLC) and MALDI-MS revealed that the degrees of polymerization of products are mostly less than 13, which indicated it's suitable for animal feed and industry. This study is the first report on the cloning, and heterogenous expression of an endo-1, 4-β-mannosidase from Bacillus subtilis HB002 in Pichia pastoris. In addition, the expression level of this endo-1, 4-β-mannosidase increases dramatically when the AOX1 promoter and α-mating factor signal of Sacchromyces cerevisiae in the Pichia pastoris expression system are replaced with the combination of d1+2x201 AOX1 promoter and the MF4I signal peptide coding sequence, respectively. This improvement implies a potential of its application in large-scale.
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来源于枯草芽孢杆菌HB002的内切-β-1,4-甘露糖苷酶编码基因在毕赤酵母中的克隆和蛋白表达
摘要:【背景】β-1,4-糖苷内切酶(E.C. 3.2.1.78)也被称为甘露聚糖酶,主要催化水解甘露糖和杂多糖主链中的β-1,4-糖苷键。因此,甘露聚糖酶不仅被广泛的应用于科学研究,也被应用于工业生产。很多生物都可以生产甘露聚糖酶,比如细菌、真菌、植物、动物。枯草芽孢杆菌是该酶的主要来源。来源于枯草芽孢杆菌HB002菌株的甘露聚糖酶属于水解酶类26族。【方法】编码该酶的基因首次被用基因枪法从基因组中克隆得到。该酶在AOX1启动子、d1+2x201 AOX1 启动子与 MF4I信号肽组合的调控下,在巴斯德毕赤酵母GS115中分别都实现了异源表达。【结果】该酶的表达主要通过SDS-PAGE检测和平板筛选。其分子量约为42 kDa,蛋白浓度为0.25 mg/mL,活性为222 U/mL。通过分子该酶的特性,采用刺槐豆胶作为底物,最适pH在5.6-7.0,最适温度为55 C。该酶在广泛的pH和温度范围内都能保持稳定,在pH 5.0-7.0条件下,室温孵育5小时,酶活仍然稳定;在50 C孵育10小时,仍有95%残余活性。并且,该酶对于半乳甘露糖和魔芋粉有很强的底物特异性。同时,该酶能被Co2+和 Mn2+强烈抑制,但对其他的金属离子不敏感。通过薄层层析(TLC)和基质辅助激光解吸电离质谱(MALDI-MS)检测数据表明,产物的聚合度低于13。该聚合度的产物适用于动物饲料工业。【结论】本研究首次实现了来源于枯草芽孢杆菌HB002菌株的β-1,4-糖苷内切酶在毕赤酵母中的异源表达。同时,用d1+2x201 AOX1 启动子和 MF4I 信号肽替换毕赤酵母表达系统中的AOX1启动子和酿酒酵母α因子信号肽之后,β-1,4-糖苷内切酶的表达水平得到了显著的提高。此改进,预示着β-1,4-糖苷内切酶的大规模应用存在一定的潜能。
关键词: β-1,4-糖苷内切酶 枯草芽孢杆菌HB002菌株 d1+2x201 AOX1 启动子 MF4I信号肽 毕赤酵母
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来源于枯草芽孢杆菌HB002的内切-β-1,4-甘露糖苷酶编码基因在毕赤酵母中的克隆和蛋白表达
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