title: The structural basis for catalysis and specificity of the Pseudomonas cellulosa alpha-glucuronidase, GlcA67A.
abstract: Alpha-glucuronidases, components of an ensemble of enzymes central to the recycling of photosynthetic biomass, remove the alpha-1,2 linked 4-O-methyl glucuronic acid from xylans. The structure of the alpha-glucuronidase, GlcA67A, from Pseudomonas cellulosa reveals three domains, the central of which is a (beta/alpha)(8) barrel housing the catalytic apparatus. Complexes of the enzyme with the individual reaction products, either xylobiose or glucuronic acid, and the ternary complex of both glucuronic acid and xylotriose reveal a "blind" pocket which selects for short decorated xylooligosaccharides substituted with the uronic acid at their nonreducing end, consistent with kinetic data. The catalytic center reveals a constellation of carboxylates; Glu292 is poised to provide protonic assistance to leaving group departure with Glu393 and Asp365 both appropriately positioned to provide base-catalyzed assistance for inverting nucleophilic attack by water.
authors.affiliation: Structural Biology Laboratory, Department of Chemistry, The University of York, Heslington, United Kingdom.
authors.forename: Didier
authors.initials: D
authors.lastname: Nurizzo
authors.forename: Tibor
authors.initials: T
authors.lastname: Nagy
authors.forename: Harry J
authors.initials: HJ
authors.lastname: Gilbert
authors.forename: Gideon J
authors.initials: GJ
authors.lastname: Davies
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D006026:Glycoside Hydrolases / Q000737:chemistry* / Q000378:metabolism*; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D011549:Pseudomonas / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D008024:Ligands; D006026:Glycoside Hydrolases; C096734:alpha-glucuronidase