title: Digital screening methodology for the directed evolution of transglycosidases.
abstract: Engineering of glycosidases with efficient transglycosidases activity is an alternative to glycosyltransferases or glycosynthases for the synthesis of oligosaccharides and glycoconjugates. However, the engineering of transglycosidases by directed evolution methodologies is hampered by the lack of efficient screening systems for sugar-transfer activity. We report here the development of digital imaging-based high-throughput screening methodology for the directed evolution of glycosidases into transgalactosidases. Using this methodology, we detected transglycosidase mutants in intact Escherichia coli cells by digital imaging monitoring of the activation of non- or low-hydrolytic mutants by an acceptor substrate. We screened several libraries of mutants of beta-glycosidase from Thermus thermophilus using this methodology and found variants with up to a 70-fold overall increase in the transglycosidase/hydrolysis activity ratio. Using natural disaccharide acceptors, these transglycosidase mutants were able to synthesise trisaccharides, as a mixture of two regioisomers, with up to 76% yield.
authors.affiliation: Biotechnologie, Biocatalyse, Biorégulation, Faculté des Sciences et des Techniques, Université de Nantes, UMR CNRS 6204, 2, rue de la Houssinière, BP 92208, Nantes, F-44322 France.
authors.forename: Fankroma M T
authors.initials: FM
authors.lastname: Koné
authors.forename: Mickaël
authors.initials: M
authors.lastname: Le Béchec
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Sine
authors.forename: Michel
authors.initials: M
authors.lastname: Dion
authors.forename: Charles
authors.initials: C
authors.lastname: Tellier
mesh_terms: D020134:Catalytic Domain; D019020:Directed Molecular Evolution / Q000379:methods*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D006026:Glycoside Hydrolases / Q000737:chemistry* / Q000235:genetics; D006868:Hydrolysis; D007700:Kinetics; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000235:genetics; D009154:Mutation; D010957:Plasmids; D015202:Protein Engineering / Q000379:methods*; D016963:Thermus thermophilus / Q000201:enzymology* / Q000235:genetics; D014166:Transferases / Q000737:chemistry* / Q000235:genetics
chemical_list: D009097:Multienzyme Complexes; C023176:transglycosidase enzyme system; D014166:Transferases; D006026:Glycoside Hydrolases