烟曲霉FC2-2木聚糖酶基因的大肠杆菌表达产物的表征

Characterization of the Translated Product of a Xylanase Gene from Aspergillus fumigatus FC2-2 in Escherichia coli

本研究对烟曲霉FC2-2的一个木聚糖酶基因Afxyn A在大肠杆菌中的表达产物进行了表征。重组木聚糖酶r Afxyn A最适p H为7.0,在p H 3.0~11.0的范围内都能保持60%以上的酶活力。r Afxyn A最适温度为50℃,在55℃以及60℃时酶活力丧失较快。EDTA对r Afxyn A酶活力具有促进作用,SDS、Ag+及Cu2+对r Afxyn A具有强烈的抑制作用。r Afxyn A对桦木木聚糖的酶动力学参数Km为(2.55±0.10)mg/m L,Vmax为(2 563±115.3)U/mg蛋白。r Afxyn A能够水解木聚糖,形成以木二糖为主的水解产物。r Afxyn A能够水解木三糖、木四糖、木五糖、木六糖等,水解的效率随聚合度的增加而增加。木聚糖酶基因Afxyn A的表达产物的特性分析对于研究该基因的工业化应用具有重要的意义。

In this study, the translated product of the gene Afxyn A encoding a xylanase, cloned from Aspergillus fumigatus FC2-2, expressed in Escherichia coli was biochemically charactered. The optimum p H of recombinant xylanase r Afxyn A was p H 7.0, stable at p H 3.0~11.0 with residual activity over 60%. The optimum temperature was 50℃. SDS, Ag+and Cu2+could inhibit the activity of r Afxyn A. The Kmand Vmaxof r Afxyn A on birchwood xylan was(2.55±0.10) mg/m L and(2 563±115.3) U/mg of protein, respectively. r Afxyn A could hydrolyze xylan into mainly xylobiose. r Afxyn A could digest xylotriose, xylotetraose, xylopentaose, and xylohexaose, the hydrolysis rate increased along with the degree of polymerization. Characterization of the expressed xylanase is important for industrial application of this xylanase gene.