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嗜碱芽孢杆菌(Bacillus halodurans)C-125菌株的基因组中,一个编码木糖苷酶的基因(BH1068)被克隆并在大肠杆菌中获得高效表达。通过全面分析纯化蛋白,确证了它的木糖苷酶功能。该酶在pH4～9的范围内保持稳定,最适pH值为中性,有较宽的最适温度(35°C～45°C),且能在45°C范围内保持稳定。这些特性使得该酶可在较为宽广的条件下对木聚糖进行酶促降解。该酶对人工合成底物对硝基苯-β-木糖苷(p-nitrophenyl-β-xylose,pNPX)的比活力为174mU/mg蛋白质,且木糖对其反馈抑制较弱(抑制常数Ki为300mmol/L)。结果显示该酶是活性较高且较耐木糖抑制的细菌源木糖苷酶。该酶与商品化的木聚糖酶一起水解山毛举木聚糖(Beechwood xylan)时显示了增效作用,且水解率可获40%。该酶最适pH为中性,对木糖耐受等特性与大多数来源于真菌、最适pH为酸性、对木糖敏感的木糖苷酶将有较好的互补。结果表明该酶在木聚糖或含木聚糖多糖的单糖化过程可能发挥重要作用。
In the genome of Bacillus halodurans C-125 strain, a gene encoding xylosidase (BH1068) was cloned and highly expressed in E. coli. Through a comprehensive analysis of the purified protein, confirmed its xylosidase function. The enzyme is stable in the pH range of 4 to 9, with optimal pH neutrality, a wide optimum temperature (35 ° C ~ 45 ° C) and stable at 45 ° C. These properties allow the enzyme to enzymatically degrade xylan under a wide range of conditions. The specific activity of the enzyme on synthetic substrate p-nitrophenyl-β-xylose (pNPX) was 174mU / mg protein, and the inhibition of xylose to it was weak 300 mmol / L). The results show that the enzyme is a more active and xylose-resistant bacterial source xylosidase. This enzyme shows synergism when hydrolyzed with Beechwood xylan with a commercial xylanase with a 40% hydrolysis rate. The optimum pH of the enzyme is neutral, tolerance to xylose and other characteristics and most derived from fungi, the optimum pH is acidic, xylose-sensitive xylosidase will have better complementarity. The results show that the enzyme may play an important role in the monosaccharide of xylan or xylan-containing polysaccharides.