Faculty of Chemistry, Biotechnology, and Food Science, Norwegian University of Life Sciences (NMBU), Ås, Norway.
Department of Biological Sciences and K. G. Jebsen Centre for Deep Sea Research, University of Bergen, Bergen, Norway.
Appl Environ Microbiol. 2019 Mar 6;85(6). doi: 10.1128/AEM.02970-18. Print 2019 Mar 15.
A two-domain GH10 xylanase-encoding gene () was discovered from a metagenomic data set, generated after incubation of a lignocellulosic substrate in hot sediments on the sea floor of the Arctic Mid-Ocean Ridge (AMOR). AMOR_GH10A comprises a signal peptide, a carbohydrate-binding module belonging to a previously uncharacterized family, and a catalytic glycosyl hydrolase (GH10) domain. The enzyme shares the highest sequence identity (42%) with a hypothetical protein from a bacterium, and its GH10 domain shares low identity (24 to 28%) with functionally characterized xylanases. Purified AMOR_GH10A showed thermophilic and halophilic properties and was active toward various xylans. Uniquely, the enzyme showed high activity toward amorphous cellulose, glucomannan, and xyloglucan and was more active toward cellopentaose than toward xylopentaose. Binding assays showed that the N-terminal domain of this broad-specificity GH10 binds strongly to amorphous cellulose, as well as to microcrystalline cellulose, birchwood glucuronoxylan, barley β-glucan, and konjac glucomannan, confirming its classification as a novel CBM (CBM85). Hot springs at the sea bottom harbor unique biodiversity and are a promising source of enzymes with interesting properties. We describe the functional characterization of a thermophilic and halophilic multidomain xylanase originating from the Arctic Mid-Ocean Ridge vent system, belonging to the well-studied family 10 of glycosyl hydrolases (GH10). This xylanase, AMOR_GH10A, has a surprisingly wide substrate range and is more active toward cellopentaose than toward xylopentaose. This substrate promiscuity is unique for the GH10 family and could prove useful in industrial applications. Emphasizing the versatility of AMOR_GH10A, its N-terminal domain binds to both xylans and glycans, while not showing significant sequence similarities to any known carbohydrate-binding module (CBM) in the CAZy database. Thus, this N-terminal domain lays the foundation for the new CBM85 family.
从海洋中洋脊海底热沉积物木质纤维素底物发酵的宏基因组数据集中，发现了一个具有两个结构域的 GH10 木聚糖酶编码基因 ()。AMOR_GH10A 包括一个信号肽、一个属于尚未鉴定的家族的碳水化合物结合模块和一个催化糖苷水解酶 (GH10) 结构域。该酶与一种假定的细菌蛋白具有最高的序列同一性 (42%)，其 GH10 结构域与功能鉴定的木聚糖酶具有低同一性 (24 至 28%)。纯化的 AMOR_GH10A 表现出嗜热和嗜盐特性，对各种木聚糖具有活性。独特的是，该酶对无定形纤维素、葡甘露聚糖和木葡聚糖表现出高活性，对纤维五糖的活性比对木五糖的活性更高。结合实验表明，该宽特异性 GH10 的 N 端结构域与无定形纤维素以及微晶纤维素、桦木木聚糖、大麦 β-葡聚糖和魔芋葡甘露聚糖强烈结合，证实其分类为新型 CBM (CBM85)。海底温泉拥有独特的生物多样性，是具有有趣特性的酶的有前途的来源。我们描述了一种源自北极中洋脊喷口系统的嗜热和嗜盐多结构域木聚糖酶的功能特征，该酶属于研究充分的糖苷水解酶 10 家族 (GH10)。这种木聚糖酶，AMOR_GH10A，具有令人惊讶的广泛底物范围，对纤维五糖的活性比对木五糖的活性更高。这种底物的混杂性是 GH10 家族所特有的，在工业应用中可能很有用。强调 AMOR_GH10A 的多功能性，其 N 端结构域与木聚糖和聚糖结合，而与 CAZy 数据库中任何已知的碳水化合物结合模块 (CBM) 没有显著的序列相似性。因此，这个 N 端结构域为新的 CBM85 家族奠定了基础。
