The beta-D-xylosidase of Trichoderma reesei is a multifunctional beta-D-xylan xylohydrolase
The beta-D-xylosidase of Trichoderma reesei is a multifunctional beta-D-xylan xylohydrolase
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DOI：
10.1042/bj3210375
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发表时间：
1997-01-15
影响因子：
4.1
通讯作者：
Kubicek, CP
中科院分区：
文献类型：
--
作者：
Herrmann, MC;Vrsanska, M;Kubicek, CP
从里氏木霉RUT C-30中纯化了一种细胞外多功能β - d -木聚糖木糖水解酶，以前称为β -木糖苷酶。活性酶为100 (+/-5)kDa糖基化单体，pI为4.7。其活性在pH为4时最优，在pH为3 ~ 6时稳定。它的温度稳定性中等（在50℃下60 min后仍有70%的活性），在60℃下活性最佳。它能水解β -1,4-低聚木糖[聚合度（DP） 2-7]，表观V-max随链长增加而增加。该酶还攻击脱支山毛榉木聚糖和4- o -甲基葡萄糖醛酸氧聚糖，形成木糖作为唯一的最终产物。木聚糖的K-m为0.7 g/l。因此，我们认为这种酶是一种β - d -木聚糖木水解酶。该酶对4-硝基- l -阿拉伯糖醛酸苷也表现出α - l -阿拉伯糖醛酸苷酶活性，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低聚木糖和高浓度的4-硝基苯- d -木pyranoside （4- nph - β -xyl）具有糖基转移酶活性。该酶水解- 1,4键优先于-1,3键，而-1,2键的低聚木糖根本不被水解。该酶能释放末端与2- o取代木吡喃糖残基相连的-1,4-木吡喃糖残基，但不能释放与3- o取代木吡喃糖残基相连的末端-1,4-木吡喃糖残基。该酶不攻击甲基、甲基1-硫代、苄基或丁基1-硫代- d -木pyrano苷和4-萘基、2-萘基和苯基- d -木pyrano苷。
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 pI 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% 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-xylooligosaccharides [degree of polymerization (DP) 2-7], the apparent V-max 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 xylooligosaccharides 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 1-thio-beta-D-xylopyranosides and 4-naphthyl, 2-naphthyl and phenyl beta-D-xylopyranosides.