Fathallah Walid, Puchart Vladimír
Institute of Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 845 38, Bratislava, Slovakia.
Faculty of Science, Beni-Suef University, Beni-Suef, 625 11, Egypt.
AMB Express. 2024 Jul 20;14(1):83. doi: 10.1186/s13568-024-01738-9.
Bifidobacterium adolescentis gene BAD_1527 has previously been suggested to code for a β-xylosidase (Kobayashi et al., Mar Drugs 18:174, 2020). Our detailed investigation of the substrate specificity of the GH43_22 protein using a wide spectrum of natural and artificial substrates showed that the enzyme hydrolyzed neither linear xylooligosaccharides nor glucuronoxylan. Xylose was released only from the artificial 4-nitrophenyl β-D-xylopyranoside (1.58 mU/mg). The corresponding α-L-arabinofuranoside was by three orders of magnitude better substrate (2.17 U/mg). Arabinose was the only monosaccharide liberated from arabinoxylan and α-1,3- or α-1,2-singly arabinosylated xylooligosaccharides. Moreover, the enzyme efficiently debranched sugar beet arabinan and singly arabinosylated α-1,5-L-arabinooligosaccharides, although short linear α-1,5-L-arabinooligosaccharides were also slowly degraded. On the other hand, debranched arabinan, arabinogalactan as well as 2,3-doubly arabinosylated main chain residues of arabinan and arabinoxylan did not serve as substrates. Thus, the enzyme encoded by the BAD_1527 gene is a typical α-L-arabinofuranosidase of AXH-m specificity.
青春双歧杆菌基因BAD_1527此前被认为编码一种β-木糖苷酶（Kobayashi等人，《海洋药物》18:174，2020年）。我们使用多种天然和人工底物对GH43_22蛋白的底物特异性进行了详细研究，结果表明该酶既不水解线性木寡糖，也不水解葡糖醛酸木聚糖。仅从人工合成的4-硝基苯基β-D-吡喃木糖苷中释放出木糖（1.58 mU/mg）。相应的α-L-阿拉伯呋喃糖苷是一种更好的底物，活性高三个数量级（2.17 U/mg）。阿拉伯糖是从阿拉伯木聚糖和α-1,3-或α-1,2-单阿拉伯糖基化木寡糖中释放出的唯一单糖。此外，该酶能有效地使甜菜阿拉伯聚糖和单阿拉伯糖基化的α-1,5-L-阿拉伯寡糖去分支，尽管短的线性α-1,5-L-阿拉伯寡糖也会缓慢降解。另一方面，去分支的阿拉伯聚糖、阿拉伯半乳聚糖以及阿拉伯聚糖和阿拉伯木聚糖的2,3-双阿拉伯糖基化主链残基都不是底物。因此，BAD_1527基因编码的酶是一种典型的具有AXH-m特异性的α-L-阿拉伯呋喃糖苷酶。
