链霉菌Z18中一种木聚糖酶(XynA)的纯化和性质

Purification and Properties of A Xylanase(XynA) Produced by Streptomyces sp. Z18

研究了链霉菌Z18中一种低分子质量木聚糖酶（XynA）的纯化和性质。粗酶液经过20％-50％硫酸铵沉淀和S-300凝胶过滤两步纯化得到电泳纯的XynA，分子质量为22ku，最适pH值为7．0，pH值稳定范围在5．0-8．0之间；最适温度为60℃，稳定温度为50℃。XynA对不同木聚糖表现出较高的活力，对其它所试底物无活性。XynA水解桦木木聚糖的主要产物为木二糖和木三糖，无木糖生成，说明它适合应用于低聚木糖的生产。

A low-molecular xylanase （XynA） produced by Streptomyces sp. Z18 was purified and characterized in this study. XynA was purified by 20 % -50 % ammonium sulfate precipitation and Sephacryl S-300 gel filtration chromatography. The denatured molecular weight of XynA was 22 ku. The optimal temperature and pH value for xylanase activity were 60℃ and 7.0, respectively. The xylanase was stable within pH value 5.0-8.0 and up to 50℃. XynA exhibited high specificity toward different xylans and low or no activity toward other substrates tested. The hydrolysis of birehwood xylan yielded mainly xylobiose and xylotriose, no xylose was detected by TLC. Therefore, XynA may be suitable for production of xylooligosaecharides.