Industrial Biotechnology & Biocatalysis Group, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, Athens, Greece.
Laboratory of Structural Biology and Biotechnology, Department of Chemical Engineering, University of Patras, Patras, Greece.
Carbohydr Polym. 2023 Apr 1;305:120527. doi: 10.1016/j.carbpol.2022.120527. Epub 2023 Jan 4.
Acetyl substitutions are common on the hemicellulosic structures of lignocellulose, which up until recently were known to inhibit xylanase activity. Emerging data, however, suggest that xylanases are able to accommodate acetyl side-groups within their catalytic site. In the present work, a fungal GH30 xylanase from Thermothelomyces thermophila, namely TtXyn30A, was shown to release acetylated xylobiose when acting on pretreated lignocellulosic substrate. The released disaccharides could be acetylated at the 2-OH, 3-OH or both positions of the non-reducing end xylose, but the existence of the acetylation on the reducing end cannot be excluded. The synergy of TtXyn30A with acetyl esterases indicates that particular subsites within its active site cannot tolerate acetylated xylopyranose residues. Molecular docking showed that acetyl group can be accommodated on the 2- or 3-OH position of the non-reducing end xylose, unlike the reducing-end xylose (subsite -1), where only 3-OH decoration can be accommodated. Such insight into the catalytic activity of TtXyn30A could contribute to a better understanding of its biological role and thus lead to a more sufficient biotechnological utilization.
乙酰取代基常见于木质纤维素的半纤维素结构中，这些结构在最近之前被认为会抑制木聚糖酶的活性。然而，新出现的数据表明，木聚糖酶能够在其催化位点容纳乙酰侧基。在本工作中，来自嗜热真菌Thermothelomyces thermophila 的真菌 GH30 木聚糖酶，即 TtXyn30A，当作用于预处理的木质纤维素底物时，被证明能够释放乙酰化的木二糖。释放的二糖可以在非还原端木糖的 2-OH、3-OH 或两个位置乙酰化，但不能排除还原端的乙酰化存在。TtXyn30A 与乙酰酯酶的协同作用表明，其活性位点内的特定亚位点不能耐受乙酰化的木吡喃糖残基。分子对接表明，乙酰基可以容纳在非还原端木糖的 2-OH 或 3-OH 位置，而不同于还原端木糖（亚位点-1），那里只能容纳 3-OH 修饰。对 TtXyn30A 催化活性的这种深入了解有助于更好地理解其生物学作用，从而导致更充分的生物技术利用。
