aguA, the gene encoding an extracellular α-glucuronidase from Aspergillus tubingensis, is specifically induced on xylose and not on glucuronic acid
aguA, the gene encoding an extracellular α-glucuronidase from Aspergillus tubingensis, is specifically induced on xylose and not on glucuronic acid
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DOI：
10.1128/jb.180.2.243-249.1998
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发表时间：
1998-01-01
影响因子：
3.2
通讯作者：
Visser, J
中科院分区：
文献类型：
--
作者：
de Vries, RP;Poulsen, CH;Visser, J
从市售曲霉属制剂和塔宾曲霉的培养滤液中纯化并表征了胞外α-葡糖醛酸酶。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳测定该酶的分子量为107 kDa，质谱测定的分子量为112 kDa，测定的pI略低于5.2，在pH6.0下长期稳定。该酶的最适pH为4.5 - 6.0，最适温度为70 ℃。α-葡糖醛酸糖苷酶主要对小的取代的木低聚物有活性，但也能从桦木木聚糖中释放少量的4-O-甲基葡糖醛酸。该酶在木聚糖的水解中与内切木聚糖酶和β-木糖苷酶协同作用。该酶是N-糖基化的，含有14个推定的N-糖基化位点。该基因编码的α-葡萄糖醛酸酶（aguA）是从A. tubingensis）。它由一个2，523 bp的开放阅读框组成，不含内含子。该基因编码841个氨基酸的蛋白质，包含20个氨基酸的真核信号序列。成熟蛋白的预测分子量为91，790 Da，计算的pi为5.13。将该基因的多个拷贝导入A. tubingensis，并在高度过量生产的转化体中研究表达。aguA基因在木糖、木二糖和木聚糖上表达，类似于编码内切木聚糖酶的基因，提示木聚糖酶和α-葡糖醛酸糖苷酶的表达的协调调节。葡萄糖醛酸不诱导aguA的表达，也不调节木糖上的表达。添加葡萄糖阻止了aguA在木聚糖上的表达，但仅降低了在木糖上的表达。
An extracellular alpha-glucuronidase was purified and characterized from a commercial Aspergillus preparation and from culture filtrate of Aspergillus tubingensis. The enzyme has a molecular mass of 107 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 112 kDa as determined by mass spectrometry, has a determined pI just below 5.2, and is stable at pH 6.0 for prolonged times. The pH optimum for the enzyme is between 4.5 and 6.0, and the temperature optimum is 70 degrees C. The a-glucuronidase is active mainly on small substituted xylo-oligomers but is also able to release a small amount of 4-O-methylglucuronic acid from birchwood xylan. The enzyme acts synergistically with endoxylanases and beta-xylosidase in the hydrolysis of xylan. The enzyme is N glycosylated and contains 14 putative N-glycosylation sites. The gene encoding this a-glucuronidase (aguA) was cloned from A. tubingensis. It consists of an open reading frame of 2,523 bp and contains no introns. The gene codes for a protein of 841 amino acids, containing a eukaryotic signal sequence of 20 amino acids. The mature protein has a predicted molecular mass of 91,790 Da and a calculated pi of 5.13. Multiple copies of the gene were introduced in A. tubingensis, and expression was studied in a highly overproducing transformant. The aguA gene was expressed on xylose, xylobiose, and xylan, similarly to genes encoding endoxylanases, suggesting a coordinate regulation of expression of xylanases and a-glucuronidase. Glucuronic acid did not induce the expression of aguA and also did not modulate the expression on xylose. Addition of glucose prevented expression of aguA on xylan but only reduced the expression on xylose.