Herrmann M C, Vrsanska M, Jurickova M, Hirsch J, Biely P, Kubicek C P
Section Microbial Biochemistry, Institute of Biochemical Technology and Microbiology, Wien, Austria.
Biochem J. 1997 Jan 15;321 ( Pt 2)(Pt 2):375-81. doi: 10.1042/bj3210375.
An extracellular multifunctional beta-D-xylan xylohydrolase, previously described as beta-xylosidase, was purified from Trichoderma reesei RUT C-30 to physical homogeneity. The active enzyme was a 100 (+/-5) kDa glycosylated monomer that exhibited a pl of 4.7. Its activity was optimal at pH 4 and it was stable between pH 3 and 6. Its temperature-stability was moderate (70 degrees zero of activity remaining after 60 min at 50 degrees C) and optimal activity was observed at 60 degrees C. It is capable of hydrolysing beta-1.4-xylo-oligosaccharides [degree of polymerization (DP) 2-7], the apparent Vmax increasing with increasing chain length. The enzyme also attacked debranched beech-wood (Lenzing) xylan and 4-O-methylglucuronoxylan, forming xylose as the only end product. The K(m) for xylan was 0.7 g/l. For this reason we consider the enzyme to be a beta-D-xylan xylohydrolase. The enzyme also exhibits alpha-L-arabinofuranosidase activity on 4-nitrophenyl alpha-L-arabinofuranoside, and evidence is presented that this is not caused by an impurity in the enzyme preparation. The beta-D-xylan xylohydrolase exhibits glycosyltransferase activity with xylo-oligosaccharides and at high concentrations of 4-nitrophenyl beta-D-xylopyranoside (4-Nph-beta-Xyl). The enzyme hydrolyses beta-1, 4-linkages preferentially to beta-1,3-linkages, and beta-1,2-linked xylo-oligosaccharides are not hydrolysed at all. The enzyme liberates terminal beta-1,4-xylopyranose residues linked to a 2-O-substituted xylopyranose residue, but not that linked to a 3-O-substituted xylopyranose residue. The enzyme does not attack methyl, methyl 1-thio-benzyl or butyl l-thio-beta-D-xylopyranosides and 4-naphthyl, 2-naphthyl and phenyl beta-D-xylopyranosides.
一种细胞外多功能β-D-木聚糖木糖水解酶，先前被描述为β-木糖苷酶，从里氏木霉RUT C-30中纯化至物理纯。活性酶是一种100（±5）kDa的糖基化单体，其pI为4.7。其活性在pH 4时最佳，在pH 3至6之间稳定。其热稳定性适中（50℃下60分钟后剩余70%的活性），在60℃时观察到最佳活性。它能够水解β-1,4-木寡糖[聚合度（DP）2-7]，表观Vmax随链长增加而增加。该酶还作用于脱支的山毛榉木（伦茨木）木聚糖和4-O-甲基葡糖醛酸木聚糖，形成木糖作为唯一的终产物。木聚糖的K(m)为0.7 g/l。因此，我们认为该酶是一种β-D-木聚糖木糖水解酶。该酶对4-硝基苯基α-L-阿拉伯呋喃糖苷还表现出α-L-阿拉伯呋喃糖苷酶活性，并且有证据表明这不是由酶制剂中的杂质引起的。β-D-木聚糖木糖水解酶对木寡糖和高浓度的4-硝基苯基β-D-木吡喃糖苷（4-Nph-β-Xyl）表现出糖基转移酶活性。该酶优先水解β-1,4-键而非β-1,3-键，并且根本不水解β-1,2-连接的木寡糖。该酶释放与2-O-取代的木吡喃糖残基相连的末端β-1,4-木吡喃糖残基，但不释放与3-O-取代的木吡喃糖残基相连的末端β-1,4-木吡喃糖残基。该酶不作用于甲基、甲基1-硫代苄基或丁基1-硫代-β-D-木吡喃糖苷以及4-萘基、2-萘基和苯基β-D-木吡喃糖苷。
