Department of Biochemistry, Faculty of Medicine, Srinakharinwirot University, 114 Sukhumvit 23, Bangkok 10110, Thailand.
Mol Biotechnol. 2013 May;54(1):37-46. doi: 10.1007/s12033-012-9541-8.
We have previously described two forms of an endo-β-1,4-xylanase (XynSW2A and XynSW2B) synthesized by thermotolerant Streptomyces sp. SWU10. Here, we describe another xylanolytic enzyme, designated XynSW1. The enzyme was purified to homogeneity from 2 L of culture filtrate. Its apparent molecular mass was 24 kDa. The optimal pH and temperature were pH 5.0 and 40 °C, respectively. The enzyme was stable in a wide pH ranges (pH 1-11), more than 80 % of initial activity remained at pH 2-11 after 16 h of incubation at 4 °C and stable up to 50 °C for 1 h. Xylobiose and xylotriose were the major xylooligosaccharides released from oat spelt xylan by the action of XynSW1, indicating of endo-type xylanase. The complete xynSW1 gene contains 1,011 bp in length and encode a polypeptide of 336 with 41 amino acids of signal peptide. The amino acid sequence analysis revealed that it belongs to glycoside hydrolase family 11 (GH11). The mature xynSW1 gene without signal peptide sequence was overexpressed in Pichia pastoris KM71H. The recombinant XynSW1 protein showed higher molecular mass due to the differences in glycosylation levels at the six N-glycosylation sites in the amino acid sequence and exhibited better physicochemical properties than those of the native enzyme including higher optimal temperature (60 °C), and specific activity, but lower optimal pH (4.0). Because of their stability in a wide pH ranges, both of native and recombinant enzymes of XynSW1, may have potential application in several industries including food, textile, biofuel, and also waste treatment.
我们之前描述了耐热链霉菌 SWU10 合成的两种内切 β-1,4-木聚糖酶（XynSW2A 和 XynSW2B）。在这里，我们描述了另一种木聚糖酶，命名为 XynSW1。该酶从 2 L 培养滤液中纯化为均相。其表观分子量为 24 kDa。最适 pH 值和温度分别为 pH5.0 和 40°C。该酶在较宽的 pH 范围内（pH1-11）稳定，在 4°C 孵育 16 小时后，超过 80%的初始活性保持在 pH2-11，并且在 50°C 下稳定 1 小时。木二糖和木三糖是 XynSW1 作用于燕麦斯佩尔特木聚糖释放的主要木寡糖，表明其为内切型木聚糖酶。完整的 xynSW1 基因长 1011bp，编码一个 336 个氨基酸的多肽，其中包含 41 个氨基酸的信号肽。氨基酸序列分析表明它属于糖苷水解酶家族 11（GH11）。成熟的 xynSW1 基因没有信号肽序列，在毕赤酵母 KM71H 中过表达。重组 XynSW1 蛋白由于氨基酸序列中六个 N-糖基化位点的糖基化水平不同，显示出更高的分子量，并且表现出比天然酶更好的物理化学性质，包括更高的最适温度（60°C）和比活，但更低的最适 pH 值（4.0）。由于它们在较宽的 pH 范围内稳定，天然和重组的 XynSW1 酶都可能在包括食品、纺织、生物燃料和废物处理在内的几个行业中具有潜在应用。
