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Publication Abstract from PubMed

beta-1,2-Glucan is an extracellular cyclic or linear polysaccharide from Gram-negative bacteria, with important roles in infection and symbiosis. Despite beta-1,2-glucan's importance in bacterial persistence and pathogenesis, only a few reports exist on enzymes acting on both cyclic and linear beta-1,2-glucan. To this end, we purified an endo-beta-1,2-glucanase to homogeneity from cell extracts of the environmental species Chitinophaga arvensicola, and an endo-beta-1,2-glucanase candidate gene (Cpin_6279) was cloned from the related species Chitinophaga pinensis The Cpin_6279 protein specifically hydrolyzed linear beta-1,2-glucan with polymerization degrees of >/=5 and a cyclic counterpart, indicating that Cpin_6279 is an endo-beta-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-beta-1,2-Glc-beta-1,2-Glc) determined up to 1.7 A revealed that it has a large cavity appropriate for polysaccharide degradation and adopts an (alpha/alpha)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 beta-1,2-glucanases and represent a critical advance toward elucidating structure-function relationships of GH enzymes.

Biochemical and structural analyses of a bacterial endo-beta-1,2-glucanase reveal a new glycoside hydrolase family.,Abe 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 J Biol Chem. 2017 May 5;292(18):7487-7506. doi: 10.1074/jbc.M116.762724. Epub, 2017 Mar 7. PMID:28270506^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.