Cloning, expression, and characterization of a novel alkali-tolerant xylanase from alkaliphilic Bacillus sp SN5
Cloning, expression, and characterization of a novel alkali-tolerant xylanase from alkaliphilic Bacillus sp SN5
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DOI：
10.1002/bab.1265
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发表时间：
2015-03-01
影响因子：
2.8
通讯作者：
Ma, Yanhe
中科院分区：
文献类型：
--
作者：
Bai, Wenqin;Xue, Yanfen;Ma, Yanhe
从嗜碱芽孢杆菌基因组文库中克隆了木聚糖酶基因(Xyn11A)。SN5.该基因编码366个氨基酸的多肽，由11家族糖苷水解酶、短连接区和36家族糖结合模块(CBM)组成。在大肠杆菌BL21(DE3)中表达了完整的木聚糖酶Xyn11A和CBM连接子截短的Xyn11A-LC。Xyn11A的最适pH为7.5，而Xyn11A-LC的最适pH范围较宽(在pH 5.5-8.5时活性为80%)，最适pH为5.5和7.5-8.0。它们具有较高的耐碱性，在37℃、pH 8.5~11.0的条件下预孵育1h后，仍能保持80%以上的剩余活力。与Xyn11A相比，Xyn11A-LC具有更好的热稳定性、更低的亲和力和更低的催化活性，但其对可溶性山毛榉木聚糖的比活性(4,511.9U/mg)高于Xyn11A(3,136.4U/mg)。这些结果表明，Xyn11A的CBM可以改变酶的性质，并在降解不溶性木聚糖方面发挥作用。Xyn11A-LC是一种高比活力的11族耐碱性纤维素酶，具有潜在的工业应用前景，尤其是在造纸工业中。(C)2014年国际生物化学和分子生物学联合会。
A xylanase gene (xyn11A) was cloned from the genomic library of alkalophilic Bacillus sp. SN5. It encoded a polypeptide of 366 amino acids, consisting of a family 11 glycoside hydrolase, a short linker region, and a family 36 carbohydrate-binding module (CBM). The intact xylanase Xyn11A and the CBM-linker-truncated Xyn11A-LC were expressed in Escherichia coli BL21 (DE3). Both purified recombinant proteins exhibited the highest activity at 55 degrees C. The optimal pH for Xyn11A activity was 7.5, whereas Xyn11A-LC showed a broad pH profile (>80% activity at pH 5.5-8.5) with optimal activity at pH 5.5 and 7.5-8.0. They had high alkali tolerance, retaining over 80% residual activity after preincubation at pH 8.5-11.0 at 37 degrees C for 1H. Xyn11A-LC showed better thermal stability, lower affinity, and lower catalytic activity to insoluble xylan than Xyn11A, whereas its specific activity for soluble beechwood xylan (4,511.9U/mg) was greater than that of Xyn11A (3,136.4U/mg). These results implied that the CBM of Xyn11A could change the enzymatic properties and play a role in degrading insoluble xylan. Xyn11A-LC is a family 11 alkali-tolerant cellulase-free xylanase with high specific activity, which qualifies it as a potential candidate for industrial applications, especially in the paper industry. (C) 2014 International Union of Biochemistry and Molecular Biology, Inc.