title: Role of asparagine 1134 in glucosidic bond and transglycosylation specificity of reuteransucrase from Lactobacillus reuteri 121.
abstract: Glucansucrases from lactic acid bacteria convert sucrose into various alpha-glucans that differ greatly with respect to the glucosidic bonds present (e.g. dextran, mutan, alternan and reuteran). This study aimed to identify the structural features of the reuteransucrase from Lactobacillus reuteri 121 (GTFA) that determine its reaction specificity. We here report a detailed mutational analysis of a conserved region immediately next to the catalytic Asp1133 (putative transition-state stabilizing) residue in GTFA. The data show that Asn1134 is the main determinant of glucosidic bond product specificity in this reuteransucrase. Furthermore, mutations at this position greatly influenced the hydrolysis/transglycosylation ratio. Changes in this amino acid expands the range of glucan and gluco-oligosaccharide products synthesized from sucrose by mutant GTFA enzymes.
authors.affiliation: Centre for Carbohydrate Bioprocessing (CCB), TNO-University of Groningen, Haren, The Netherlands.
authors.forename: Slavko
authors.initials: S
authors.lastname: Kralj
authors.forename: Wieger
authors.initials: W
authors.lastname: Eeuwema
authors.forename: Tom H
authors.initials: TH
authors.lastname: Eckhardt
authors.forename: Lubbert
authors.initials: L
authors.lastname: Dijkhuizen
mesh_terms: D001216:Asparagine / Q000502:physiology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017124:Conserved Sequence; D004926:Escherichia coli / Q000235:genetics; D005960:Glucosides / Q000737:chemistry*; D006031:Glycosylation; D016695:Glycosyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007534:Isomaltose / Q000378:metabolism; D052200:Limosilactobacillus reuteri / Q000201:enzymology* / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D009844:Oligosaccharides / Q000096:biosynthesis; D013057:Spectrum Analysis; D013379:Substrate Specificity; D013395:Sucrose / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D005960:Glucosides; D009844:Oligosaccharides; D013395:Sucrose; D007534:Isomaltose; D001216:Asparagine; D016695:Glycosyltransferases; C033837:alternansucrase