Biochemical and structural analyses of a bacterial endo-beta-1,2-glucanase reveal a new glycoside hydrolase familyAbe, K., Nakajima, M., Yamashita, T., Matsunaga, H., Kamisuki, S., Nihira, T., Takahashi, Y., Sugimoto, N., Miyanaga, A., Nakai, H., Arakawa, T., Fushinobu, S., Taguchi, H.
(2017) J Biol Chem 292: 7487-7506
- PubMed: 28270506
- DOI: 10.1074/jbc.M116.762724
- Primary Citation of Related Structures:
- PubMed Abstract:
β-1,2-Glucan is an extracellular cyclic or linear polysaccharide from Gram-negative bacteria, with important roles in infection and symbiosis. Despite β-1,2-glucan's importance in bacterial persistence and pathogenesis, only a few reports exist on en ...
β-1,2-Glucan is an extracellular cyclic or linear polysaccharide from Gram-negative bacteria, with important roles in infection and symbiosis. Despite β-1,2-glucan's importance in bacterial persistence and pathogenesis, only a few reports exist on enzymes acting on both cyclic and linear β-1,2-glucan. To this end, we purified an endo -β-1,2-glucanase to homogeneity from cell extracts of the environmental species Chitinophaga arvensicola , and an endo -β-1,2-glucanase candidate gene ( Cpin_6279 ) was cloned from the related species Chitinophaga pinensis The Cpin_6279 protein specifically hydrolyzed linear β-1,2-glucan with polymerization degrees of ≥5 and a cyclic counterpart, indicating that Cpin_6279 is an endo -β-1,2-glucananase. Stereochemical analysis demonstrated that the Cpin_6279-catalyzed reaction proceeds via an inverting mechanism. Cpin_6279 exhibited no significant sequence similarity with known glycoside hydrolases (GHs), and thus the enzyme defines a novel GH family, GH144. The crystal structures of the ligand-free and complex forms of Cpin_6279 with glucose (Glc) and sophorotriose (Glc-β-1,2-Glc-β-1,2-Glc) determined up to 1.7 Å revealed that it has a large cavity appropriate for polysaccharide degradation and adopts an (α/α) 6 -fold slightly similar to that of GH family 15 and 8 enzymes. Mutational analysis indicated that some of the highly conserved acidic residues in the active site are important for catalysis, and the Cpin_6279 active-site architecture provided insights into the substrate recognition by the enzyme. The biochemical characterization and crystal structure of this novel GH may enable discovery of other β-1,2-glucanases and represent a critical advance toward elucidating structure-function relationships of GH enzymes.
the Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510.