黑曲霉A3木聚糖酶酶学性质研究*

黑曲霉A3（AspergillusnigerA3）的固体培养物浸出液，经过多步分离纯化后，获得三个组份的木聚糖酶，称为xⅠ、xⅡ和xⅢ。经7％凝胶浓度的盘状电泳分析均为单一组份。经等电聚焦电泳测xⅠ、xⅡ和xⅢ的等电点分别为6.8、5．5和6.1。SDS－PAGE测得亚基分子量（Da）分别为xⅠ，42000；xⅡ，20000；xⅢ，3000。三个酶组份的最适反应温度分别为xⅠ，40℃i；xⅡ，50℃；xⅢ，50℃。最适反应pHxⅠ，3．5；xⅢ，4．5；xⅢ，5．0。保温一个小时后，酶的半失活温度分别为xⅠ，55.6℃；xⅡ，54.8℃；xⅢ，46.6℃。金属离子Ag+、Hg2+、Ni2+和脲对不同的酶组份具有一定的影响。

STUDIES ON THE PROPERTIES OF XYLANASES OF ASPERGILLUS NIGER A3

Three xylanases named x Ⅰ, xⅡ and xⅢ in the filtrate of solid state culture medium of Aspergillus niger were purifled by (NH4)2 SO4, alchol frachonahon, and Sephadex G-100 gel filtration and DEAE-Sephadex A-50 Ion exchange, and were homogeneous on disc PAGE. The isoelectric points of xⅠ, xⅡ and xⅢ were6.8, 5.5 and 6.1 respectively estimated by PAGIF and their molecular weighs were 42 000, 20000and 31000 Da respechvely eshmated by SDS-gel electrophoresis.x Ⅰ, xⅡ and xⅢ showed optimal activity at 40, 50 and 50℃ and pH 3.5, 4.5 and 5.0, respectively. The temperature for loss half achvity (t1/2) in 1h is 55.6℃ for xⅠ,54.8℃ for xⅡ and 46.6℃ for xⅢ. Ag+, Hg2+ and Ni2+ ion and urea showedrelative effect on the different group of xylanases.