BACKGROUND A mesophilic xylanase PjxA from Penicillium janthinellum MA21601 has high specific activity under acidic condition and holds great potential for applications in the animal feed industry. To enhance the thermostability of xylanase PjxA, two mutation strategies in the N-terminal region were examined and then integrated into the xylanase to further improvement. The recombinant xylanase PTxA-DB (The meaning of DB is disulfide-bridge.) was constructed by replacement of five residues in the mutated region in TfxA (T10Y, N11H, N12D, Y15F, N30 L), combined with an additional disulfide bridge in the N-terminal region. RESULTS The Tm value of mutant PTxA-DB was improved from 21.3 °C to 76.6 °C, and its half-life was found to be 53.6 min at 60 °C, 107-fold higher than the wild type strain. The location of the disulfide bridge (T2C-T29C) was between the irregular loop and the β-strand A2, accounting for most of the improvement in thermostability of PjxA. Further analysis indicated T2C, T29C, N30 L and Y15F lead to increase N-terminal hydrophobicity. Moreover, the specific activity and substrate affinity of PTxA-DB were also enhanced under the acidic pH values. CONCLUSIONS These results indicated PTxA-DB could be a prospective additive to industrial animal feeds.

中文翻译：

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N末端残基的诱变赋予花青霉MA21601木聚糖酶热稳定性。

背景技术来自于青霉青霉MA21601的嗜温木聚糖酶PjxA在酸性条件下具有高的比活性，并且在动物饲料工业中具有巨大的应用潜力。为了增强木聚糖酶PjxA的热稳定性，研究了N末端区域的两种突变策略，然后将其整合到木聚糖酶中以进一步改进。重组木聚糖酶PTxA-DB（DB的含义是二硫桥）是通过替换TfxA突变区（T10Y，N11H，N12D，Y15F，N30 L）中的五个残基，并结合一个额外的二硫桥而构建的。 N末端区域。结果突变体PTxA-DB的Tm值从21.3°C提高到76.6°C，在60°C下的半衰期为53.6 min，比野生型菌株高107倍。二硫键（T2C-T29C）的位置在不规则环和β链A2之间，这是PjxA热稳定性提高的大部分原因。进一步的分析表明，T2C，T29C，N30 L和Y15F导致N端疏水性增加。此外，在酸性pH值下，PTxA-DB的比活和底物亲和力也得到增强。结论这些结果表明PTxA-DB可以作为工业动物饲料的前瞻性添加剂。