Institute of Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 845 38, Bratislava, Slovakia.
Appl Microbiol Biotechnol. 2021 Jan;105(1):185-195. doi: 10.1007/s00253-020-11023-x. Epub 2020 Nov 20.
Typical bacterial GH30 xylanases are glucuronoxylanases requiring 4-O-methylglucuronic acid (MeGlcA) substitution of a xylan main chain for their action. They do not exhibit a significant activity on neutral xylooligosaccharides, arabinoxylan (AraX), or rhodymenan (Rho). In this work, the biochemical characterization of the bacterial Clocl_1795 xylanase from Hungateiclostridium (Clostridium) clariflavum DSM 19732 (HcXyn30A) is presented. Amino acid sequence analysis of HcXyn30A revealed that the enzyme does not contain amino acids known to be responsible for MeGlcA coordination in the -2b subsite of glucuronoxylanases. This suggested that the catalytic properties of HcXyn30A may differ from those of glucuronoxylanases. HcXyn30A shows similar specific activity on glucuronoxylan (GX) and Rho, while the specific activity on AraX is about 1000 times lower. HcXyn30A releases Xyl as the main product from the non-reducing end of different polymeric and oligomeric substrates. Catalytic properties of HcXyn30A resemble the properties of the fungal GH30 xylobiohydrolase from Acremonium alcalophilum, AaXyn30A. HcXyn30A is the first representative of a prokaryotic xylobiohydrolase. Its unique specificity broadens the catalytic diversity of bacterial GH30 xylanases. KEY POINTS: • Bacterial GH30 xylobiohydrolase from H. clariflavum (HcXyn30A) has been characterized. • HcXyn30A releases xylobiose from the non-reducing end of different substrates. • HcXyn30A is the first representative of bacterial xylobiohydrolase.
典型的 GH30 木聚糖酶是需要木聚糖主链 4-O-甲基葡萄糖醛酸（MeGlcA）取代才能发挥作用的葡萄糖醛酸酶。它们对中性木低聚糖、阿拉伯木聚糖（AraX）或罗得曼聚糖（Rho）没有显著的活性。在这项工作中，介绍了来自 Hungateiclostridium（Clostridium）clariflavum DSM 19732（HcXyn30A）的细菌 Clocl_1795 木聚糖酶的生化特性。HcXyn30A 的氨基酸序列分析表明，该酶不包含已知负责葡萄糖醛酸酶中木聚糖 -2b 亚位点 MeGlcA 配位的氨基酸。这表明 HcXyn30A 的催化特性可能与葡萄糖醛酸酶不同。HcXyn30A 在葡萄糖醛酸木聚糖（GX）和 Rho 上具有相似的比活性，而在 AraX 上的比活性低约 1000 倍。HcXyn30A 从不同聚合体和低聚物底物的非还原端释放 Xyl 作为主要产物。HcXyn30A 的催化特性类似于真菌 GH30 木糖苷水解酶 Acremonium alcalophilum 的 AaXyn30A。HcXyn30A 是原核木糖苷水解酶的第一个代表。它独特的特异性拓宽了细菌 GH30 木聚糖酶的催化多样性。 关键点： • 已对来自 H. clariflavum 的细菌 GH30 木糖苷水解酶（HcXyn30A）进行了表征。 • HcXyn30A 从不同底物的非还原端释放木二糖。 • HcXyn30A 是细菌木糖苷水解酶的第一个代表。
