title: Synthesis of a library of xylogluco-oligosaccharides for active-site mapping of xyloglucan endo-transglycosylase.
abstract: Complex oligosaccharides containing alpha-D-xylosyl-(1-->6)-beta-D-glucosyl residues and unsubstituted beta-(1-->4)-linked D-glucosyl units were readily synthesized using enzymatic coupling catalyzed by the Cel7B E197A glycosynthase from Humicola insolens. Constituting this library required four key steps: (1) preparing unprotected building blocks by chemical synthesis or enzymatic degradation of xyloglucan polymers; (2) generating the donor synthon in the enzymatic coupling by temporarily introducing a lactosyl motif on the 4-OH of the terminal glucosyl units of the xylogluco-oligosaccharides; (3) synthesizing the corresponding alpha-fluorides, followed by their de-O-acetylation and the glycosynthase-catalyzed condensation of these donors onto various acceptors; and (4) enzymatically releasing lactose or galactose from the reaction product, affording the target molecules in good overall yields. These complex oligosaccharides proved useful for mapping the active site of a key enzyme in plant cell wall biosynthesis and modification: the xyloglucan endo-transglycosylase (XET). We also report some preliminary enzymatic results regarding the efficiency of these compounds.
authors.affiliation: Centre de Recherche sur les Macromolécules Végétales (CERMAV-CNRS), BP53, 38041 Grenoble Cedex 9, France.
authors.forename: Régis
authors.initials: R
authors.lastname: Fauré
authors.forename: Marc
authors.initials: M
authors.lastname: Saura-Valls
authors.forename: Harry
authors.initials: H
authors.lastname: Brumer
authors.forename: Antoni
authors.initials: A
authors.lastname: Planas
authors.forename: Sylvain
authors.initials: S
authors.lastname: Cottaz
authors.forename: Hugues
authors.initials: H
authors.lastname: Driguez
mesh_terms: D001665:Binding Sites; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D020650:Combinatorial Chemistry Techniques; D016695:Glycosyltransferases / Q000737:chemistry*; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000138:chemical synthesis* / Q000737:chemistry; D013379:Substrate Specificity
chemical_list: D009844:Oligosaccharides; D016695:Glycosyltransferases; C073693:xyloglucan endotransglycosylase