Manin C, Shareek F, Morosoli R, Kluepfel D
Centre de recherche en microbiologie appliquée, Institut Armand-Frappier, Université du Québec, Laval-des-Rapides.
Biochem J. 1994 Sep 1;302 ( Pt 2)(Pt 2):443-9. doi: 10.1042/bj3020443.
The gene encoding an alpha-L-arabinofuranosidase (abfA) was homologously cloned in Streptomyces lividans and its DNA sequence was determined. The enzyme was purified from the cytoplasm of the hyperproducing clone S. lividans IAF116. Its M(r) was estimated by gel filtration and found to be approx. 380,000. Since SDS/PAGE indicated a native protein of M(r) 69,000, it can be concluded that the native protein consists of several subunits of that size. The pI value was 4.6. The kinetic constants determined with p-nitrophenyl alpha-L-arabinofuranoside as substrate were a Vmax of 180 units/mg of protein and a Km of 0.6 mM. The specific activity of the purified enzyme on this substrate was 153 units/mg of protein. Optimal enzyme activity was obtained at 60 degrees C and pH 6.0. The enzyme cleaved p-nitrophenyl alpha-L-arabinofuranoside, but had no activity on a variety of other p-nitrophenyl glycosides, except on p-nitrophenyl beta-D-xylopyranoside. The enzyme showed no activity on oat-spelts (Avena sativa) xylan or arabinogalactan, but acted on beet (Beta) arabinan or arabinoxylan. Hydrolysis occurred on arabino-oligoxylosides obtained from oat-splets xylan after digestion with xylanases. Since S. lividans normally does not secrete arabinofuranosidase, this enzyme may play a role in the assimilation of arabinose moieties from arabinose-containing xylo-oligosaccharides generated by beta-xylosidases or xylanases.
编码α-L-阿拉伯呋喃糖苷酶（abfA）的基因在淡紫链霉菌中进行了同源克隆，并测定了其DNA序列。该酶从高产克隆淡紫链霉菌IAF116的细胞质中纯化得到。通过凝胶过滤估计其相对分子质量（M(r)）约为380,000。由于SDS/PAGE显示其天然蛋白的M(r)为69,000，因此可以得出结论，天然蛋白由几个该大小的亚基组成。其等电点（pI）值为4.6。以对硝基苯基α-L-阿拉伯呋喃糖苷为底物测定的动力学常数为：最大反应速度（Vmax）为180单位/毫克蛋白，米氏常数（Km）为0.6 mM。纯化酶对该底物的比活性为153单位/毫克蛋白。在60℃和pH 6.0时可获得最佳酶活性。该酶能切割对硝基苯基α-L-阿拉伯呋喃糖苷，但对多种其他对硝基苯基糖苷无活性，除了对硝基苯基β-D-吡喃木糖苷。该酶对燕麦麸（燕麦）木聚糖或阿拉伯半乳聚糖无活性，但作用于甜菜（甜菜）阿拉伯聚糖或阿拉伯木聚糖。在用木聚糖酶消化燕麦麸木聚糖后得到的阿拉伯低聚木糖苷上会发生水解。由于淡紫链霉菌通常不分泌阿拉伯呋喃糖苷酶，该酶可能在同化由β-木糖苷酶或木聚糖酶产生的含阿拉伯糖的木寡糖中的阿拉伯糖部分时发挥作用。
