6jeb
crystal structure of a beta-N-acetylhexosaminidase
Structural highlights
FunctionH2018_AKKM8 Hydrolyzes terminal GlcNAc residues from terminally unbranched N-glycans and from chitobiose. Hydrolyzes beta-1,6-linked N-acetylglucosamine and beta-1,4-linked N-acetylgalactosamine from pNP-alpha-GalNAc[beta1,3Gal]beta1,6GlcNAc and pNP-beta-GlcNAc-beta1,4-GalNAc substrates, respectively, as well as beta-1,2-linked N-acetylglucosamine units from the non-reducing end of N-glycans. Hydrolyzes GlcNAc residues linked to alpha1,3- or alpha1,6-mannose branch, but has low activity on substrates with more than one GlcNAc residue on one of the mannose branches. Releases terminal GlcNAc moieties from the N-glycopeptide Gly-Glu-Asn-(GlcNAc2Man3GlcNAc2)-Arg with high efficiency. Has moderate hydrolytic activity on the chitobiose moiety of N-glycopeptide substrate Gly-Glu-Asn-(GlcNAc2)-Arg. Does not hydrolyze GlcNAc residues from N-glycan structures bearing a bisecting GlcNAc moiety (beta1,4-linked GlcNAc to the beta1,4-linked core mannose) (PubMed:29304441). Potentially capable of cleaving the specific glycoside linkages in the process of mucin degradation in human intestinal tract (Probable). Hydrolyzes synthetic substrate pNP-beta-GlcNAc with high activity and pNP-beta-GalNAc to a lesser extent (PubMed:29304441, PubMed:30846208). Does not hydrolyze pNP-beta-glucose, pNP-beta-galactose, pNP-alpha-glucose, pNP-alpha-galactose, pNP-alpha-GlcNAc or pNP-alpha-fucose (PubMed:29304441).[1] [2] Publication Abstract from PubMedbeta-N-acetylhexosaminidases from Akkermansia muciniphila was reported to perform the crystal structure with GlcNAc complex, which proved to be the substrate of Am2301. Domain II of Am2301 is consisted of amino acid residues 111-489 and is folded as a (beta/alpha)8 barrel with the active site combined of the glycosyl hydrolases. Crystallographic evidence showed that Asp-278 and Glu-279 could be the catalytic site and Tyr-373 may plays a role on binding the substrate. Moreover, Am2301 prefers to bind Zn ion, which similar to other GH 20 family. Enzyme activity and kinetic parameters of wild-type Am2301 and mutants proved that Asp-278 and Glu-279 are the catalytic sites and they play a critical role on the catalytic process. Overall, our results demonstrate that Am2301 and its complex with GlcNAC provide obvious structural evidence for substrate-assisted catalysis. Obviously, this expands our understanding on the mode of substrate-assisted reaction for this enzyme family in Akkermansia muciniphila. Crystallographic evidence for substrate-assisted catalysis of beta-N-acetylhexosaminidas from Akkermansia muciniphila.,Chen X, Wang J, Liu M, Yang W, Wang Y, Tang R, Zhang M Biochem Biophys Res Commun. 2019 Apr 16;511(4):833-839. doi:, 10.1016/j.bbrc.2019.02.074. Epub 2019 Mar 4. PMID:30846208[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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