Wei Lin, Cao Hai-Yan, Zou Ruyi, Du Min, Zhang Qingdong, Lu Danrong, Xu Xiangyu, Xu Yingying, Wang Wenshuang, Chen Xiu-Lan, Zhang Yu-Zhong, Li Fuchuan
National Glycoengineering Research Center and Shandong Key Laboratory of Carbohydrate Chemistry and Glycobiology, State Key Laboratory of Microbial Technology, Shandong University, Qingdao, China.
MOE Key Laboratory of Evolution and Marine Biodiversity, Frontiers Science Center for Deep Ocean Multispheres and Earth System & College of Marine Life Sciences, Ocean University of China, Qingdao, China.
Elife. 2025 May 19;13:RP102422. doi: 10.7554/eLife.102422.
Recently, a new class of glycosaminoglycan (GAG) lyases (GAGases) belonging to PL35 family has been discovered with an ultrabroad substrate spectrum that can degrade three types of uronic acid-containing GAGs (hyaluronic acid, chondroitin sulfate and heparan sulfate) or even alginate. In this study, the structures of GAGase II from and GAGase VII from DSM 17393 were determined at 1.9 and 2.4 Å resolution, respectively, and their catalytic mechanism was investigated by the site-directed mutant of their crucial residues and molecular docking assay. Structural analysis showed that GAGase II and GAGase VII consist of an N-terminal (α/α) toroid multidomain and a C-terminal two-layered β-sheet domain with Mn. Notably, although GAGases share similar folds and catalytic mechanisms with some GAG lyases and alginate lyases, they exhibit higher structural similarity with alginate lyases than GAG lyases, which may present a crucial structural evidence for the speculation that GAG lyases with (α/α) toroid and antiparallel β-sheet structures arrived by a divergent evolution from alginate lyases with the same folds. Overall, this study not only solved the structure of PL35 GAG lyases for the first time and investigated their catalytic mechanism, especially the reason why GAGase III can additionally degrade alginate, but also provided a key clue in the divergent evolution of GAG lyases that originated from alginate lyases.
最近，人们发现了一类属于PL35家族的新型糖胺聚糖（GAG）裂解酶（GAGases），其具有超宽的底物谱，能够降解三种含糖醛酸的GAG（透明质酸、硫酸软骨素和硫酸乙酰肝素），甚至藻酸盐。在本研究中，分别以1.9 Å和2.4 Å的分辨率测定了来自[具体来源1]的GAGase II和来自DSM 17393的GAGase VII的结构，并通过对其关键残基进行定点突变和分子对接分析来研究它们的催化机制。结构分析表明，GAGase II和GAGase VII由一个N端（α/α）环形多结构域和一个C端双层β折叠结构域以及锰组成。值得注意的是，尽管GAGases与一些GAG裂解酶和藻酸盐裂解酶具有相似的折叠和催化机制，但它们与藻酸盐裂解酶的结构相似性高于GAG裂解酶，这可能为推测具有（α/α）环形和反平行β折叠结构的GAG裂解酶是由具有相同折叠的藻酸盐裂解酶通过趋异进化而来提供了关键的结构证据。总体而言，本研究不仅首次解析了PL35 GAG裂解酶的结构并研究了它们的催化机制，特别是GAGase III能够额外降解藻酸盐的原因，还为源自藻酸盐裂解酶的GAG裂解酶的趋异进化提供了关键线索。
