1hp5 | pdb_00001hp5

STREPTOMYCES PLICATUS BETA-N-ACETYLHEXOSAMINIDASE COMPLEXED WITH INTERMEDIATE ANALOUGE NAG-THIAZOLINE

spinqualitylabelsall models 1hp5, resolution 2.10Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1hp5 is a 1 chain structure with sequence from Atcc 25483. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: CL, GOL, NGT, SO4 Related: 1hp4 Activity: Beta-N-acetylhexosaminidase, with EC number 3.2.1.52 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed beta-Hexosaminidase, a family 20 glycosyl hydrolase, catalyzes the removal of beta-1,4-linked N-acetylhexosamine residues from oligosaccharides and their conjugates. Heritable deficiency of this enzyme results in various forms of GalNAc-beta(1,4)-[N-acetylneuraminic acid (2,3)]-Gal-beta(1,4)-Glc-ceramide gangliosidosis, including Tay-Sachs disease. We have determined the x-ray crystal structure of a beta-hexosaminidase from Streptomyces plicatus to 2.2 A resolution (Protein Data Bank code ). beta-Hexosaminidases are believed to use a substrate-assisted catalytic mechanism that generates a cyclic oxazolinium ion intermediate. We have solved and refined a complex between the cyclic intermediate analogue N-acetylglucosamine-thiazoline and beta-hexosaminidase from S. plicatus to 2.1 A resolution (Protein Data Bank code ). Difference Fourier analysis revealed the pyranose ring of N-acetylglucosamine-thiazoline bound in the enzyme active site with a conformation close to that of a (4)C(1) chair. A tryptophan-lined hydrophobic pocket envelopes the thiazoline ring, protecting it from solvolysis at the iminium ion carbon. Within this pocket, Tyr(393) and Asp(313) appear important for positioning the 2-acetamido group of the substrate for nucleophilic attack at the anomeric center and for dispersing the positive charge distributed into the oxazolinium ring upon cyclization. This complex provides decisive structural evidence for substrate-assisted catalysis and the formation of a covalent, cyclic intermediate in family 20 beta-hexosaminidases. Crystallographic evidence for substrate-assisted catalysis in a bacterial beta-hexosaminidase.,Mark BL, Vocadlo DJ, Knapp S, Triggs-Raine BL, Withers SG, James MN J Biol Chem. 2001 Mar 30;276(13):10330-7. Epub 2000 Dec 21. PMID:11124970 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Beta-Hexosaminidase Beta-Hexosaminidase 3D structures

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