Vardakou Maria, Katapodis Petros, Samiotaki Martina, Kekos Dimitris, Panayotou George, Christakopoulos Paul
Biotechnology Laboratory, Chemical Engineering Department, National Technical University of Athens, 5 Iroon Polytechniou Str., Zografou Campus, 15700 Athens, Greece.
Int J Biol Macromol. 2003 Nov;33(1-3):129-34. doi: 10.1016/s0141-8130(03)00077-1.
Microbial endo-beta-1,4-xylanases (EXs, EC 3.2.1.8) belonging to glycanase families 10 and 11 differ in their action on water-unextractable arabinoxylan (WU-AX). WU-AX was incubated with different levels of a Thermoascus aurantiacus family 10 and a Sporotrichum thermophile family 11 endoxylanases. At 10 g l(-1) arabinoxylan, enzyme concentrations (KE values) needed to obtain half-maximal hydrolysis rates (V(max) values) were 4.4 nM for the xylanase from T. aurantiacus and 7.1 nM for the xylanase from S. thermophile. Determination of Vmax/KE revealed that the family 10 enzyme hydrolysed two times more efficiently WU-AX than the family 11 enzyme. Molecular weights of the products formed were assessed and separation of feruloyl-oligosaccharides was achieved by anion-exchange and size-exclusion chromatography (SEC). The main difference between the feruloylated products by xylanases of family 10 and 11 concerned the length of the products containing feruloyl-arabinosyl substitution. The xylanase from T. aurantiacus liberated from WU-AX a feruloyl arabinoxylodisaccharide (FAX2) as the shortest feruloylated fragment in contrast with the enzyme from S. thermophile, which liberated a feruloyl arabinoxylotrisaccharide (FAX3). These results indicated that different factors govern WU-AX breakdown by the two endoxylanases.
属于聚糖酶家族10和11的微生物内切β-1,4-木聚糖酶（EXs，EC 3.2.1.8）对水不溶性阿拉伯木聚糖（WU-AX）的作用不同。将WU-AX与不同水平的嗜热栖热菌家族10内切木聚糖酶和嗜热侧孢霉家族11内切木聚糖酶一起孵育。在10 g l(-1)阿拉伯木聚糖浓度下，获得最大水解速率一半（V(max)值）所需的酶浓度（KE值），嗜热栖热菌木聚糖酶为4.4 nM，嗜热侧孢霉木聚糖酶为7.1 nM。Vmax/KE的测定表明，家族10的酶水解WU-AX的效率是家族11酶的两倍。对形成产物的分子量进行了评估，并通过阴离子交换和尺寸排阻色谱（SEC）实现了阿魏酰寡糖的分离。家族10和11的木聚糖酶产生的阿魏酰化产物之间的主要差异在于含有阿魏酰-阿拉伯糖基取代的产物长度。嗜热栖热菌的木聚糖酶从WU-AX中释放出阿魏酰阿拉伯木二糖（FAX2）作为最短的阿魏酰化片段，而嗜热侧孢霉的酶释放出阿魏酰阿拉伯木三糖（FAX3）。这些结果表明，两种内切木聚糖酶分解WU-AX受不同因素控制。
