title: Structural analysis of enzyme-resistant isomaltooligosaccharides reveals the elongation of α-(1→3)-linked branches in Weissella confusa dextran.
abstract: Weissella confusa VTT E-90392 is an efficient producer of a dextran that is mainly composed of α-(1→6)-linked D-glucosyl units and very few α-(1→3) branch linkages. A mixture of the Chaetomium erraticum endodextranase and the Aspergillus niger α-glucosidase was used to hydrolyze W. confusa dextran to glucose and a set of enzyme-resistant isomaltooligosaccharides. Two of the oligosaccharides (tetra- and hexasaccharide) were isolated in pure form and their structures elucidated. The tetrasaccharide had a nonreducing end terminal α-(1→3)-linked glucosyl unit (α-D-Glcp-(1→3)-α-D-Glcp-(1→6)-α-D-Glcp-(1→6)-α-D-Glc), whereas the hexasaccharide had an α-(1→3)-linked isomaltosyl side group (α-D-Glcp-(1→6)[α-D-Glcp-(1→6)-α-D-Glcp-(1→3)]-α-D-Glcp-(1→6)-α-D-Glcp-(1→6)-α-D-Glc). A mixture of two isomeric oligosaccharides was also obtained in the pentasaccharide fraction, which were identified as (α-D-Glcp-(1→6)-α-D-Glcp-(1→3)-α-D-Glcp-(1→6)-α-D-Glcp-(1→6)-α-D-Glc) and (α-D-Glcp-(1→6)[α-D-Glcp-(1→3)]-α-D-Glcp-(1→6)-α-D-Glcp-(1→6)-α-D-Glc). The structures of the oligosaccharides indicated that W. confusa dextran contains both terminal and elongated α-(1→3)-branches. This is the first report evidencing the presence of elongated branches in W. confusa dextran. The (1)H and (13)C NMR spectroscopic data on the enzyme-resistant isomaltooligosaccharides with α-(1→3)-linked glucosyl and isomaltosyl groups are published here for the first time.
authors.affiliation: Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland. henry.maina@helsinki.fi
authors.forename: Ndegwa Henry
authors.initials: NH
authors.lastname: Maina
authors.forename: Liisa
authors.initials: L
authors.lastname: Virkki
authors.forename: Henna
authors.initials: H
authors.lastname: Pynnönen
authors.forename: Hannu
authors.initials: H
authors.lastname: Maaheimo
authors.forename: Maija
authors.initials: M
authors.lastname: Tenkanen
mesh_terms: D001234:Aspergillus niger / Q000201:enzymology; D002236:Carbohydrate Conformation; D002597:Chaetomium / Q000201:enzymology; D003910:Dextranase / Q000037:antagonists & inhibitors / Q000378:metabolism; D003911:Dextrans / Q000737:chemistry*; D065089:Glycoside Hydrolase Inhibitors; D006868:Hydrolysis; D056584:Leuconostocaceae / Q000737:chemistry*; D009844:Oligosaccharides / Q000737:chemistry* / Q000494:pharmacology; D000520:alpha-Glucosidases / Q000378:metabolism
chemical_list: D003911:Dextrans; D065089:Glycoside Hydrolase Inhibitors; D009844:Oligosaccharides; D003910:Dextranase; D000520:alpha-Glucosidases