Department of Chemistry, University of California, Davis, CA, USA.
Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.
FEBS Lett. 2020 Feb;594(3):439-451. doi: 10.1002/1873-3468.13618. Epub 2019 Oct 8.
While multiple α 1-2-mannosidases are necessary for glycoprotein N-glycan maturation in vertebrates, a single bacterial α1-2-mannosidase can be sufficient to cleave all α1-2-linked mannose residues in host glycoprotein N-glycans. We report here the characterization and crystal structure of a new α1-2-mannosidase (EfMan-I) from Enterococcus faecalis, a Gram-positive opportunistic human pathogen. EfMan-I catalyzes the cleavage of α1-2-mannose from not only oligomannoses but also high-mannose-type N-glycans on glycoproteins. Its 2.15 Å resolution crystal structure reveals a two-domain enzyme fold similar to other CAZy GH92 mannosidases. An unexpected potassium ion was observed bridging two domains near the active site. These findings support EfMan-I as an effective catalyst for in vitro N-glycan modification of glycoproteins with high-mannose-type N-glycans.
虽然脊椎动物中多种 α 1-2-甘露糖苷酶对于糖蛋白 N-聚糖的成熟是必需的，但单个细菌 α 1-2-甘露糖苷酶就足以切割宿主糖蛋白 N-聚糖中所有的 α1-2 连接的甘露糖残基。本文报道了来自粪肠球菌的新型 α 1-2-甘露糖苷酶（EfMan-I）的特性和晶体结构，粪肠球菌是一种革兰氏阳性机会性病原体。EfMan-I 不仅可以催化寡甘露糖，还可以催化糖蛋白上高甘露糖型 N-聚糖中 α1-2-甘露糖的切割。其 2.15 Å 分辨率的晶体结构揭示了一种类似于其他 CAZy GH92 甘露糖苷酶的双结构域酶折叠。在靠近活性位点的地方观察到一个意想不到的钾离子桥接两个结构域。这些发现支持 EfMan-I 作为有效催化剂，用于体外修饰具有高甘露糖型 N-聚糖的糖蛋白。
