title: Synthesis of New Hyperbranched α-Glucans from Sucrose by Lactobacillus reuteri 180 Glucansucrase Mutants.
abstract: α-Glucans produced by glucansucrase enzymes of lactic acid bacteria attract strong attention as novel ingredients and functional biopolymers in the food industry. In the present study, α-helix 4 amino acid residues D1085, R1088, and N1089 of glucansucrase GTF180 of Lactobacillus reuteri 180 were targeted for mutagenesis both jointly and separately. Analysis of the mutational effects on enzyme function revealed that all D1085 and R1088 mutants catalyzed the synthesis of hyperbranched α-glucans with 15-22% branching (α1→3,6) linkages, compared to 13% in the wild-type GTF180. In addition, besides native (α1→6) and (α1→3) linkages, all of the mutations introduced a small amount of (α1→4) linkages (5% at most) in the polysaccharides produced. We conclude that α-helix 4 residues, especially D1085 and R1088, constituting part of the +2 acceptor binding subsite, are important determinants for the linkage specificity. The new hyperbranched α-glucans provide very interesting structural diversities and may find applications in the food industry.
authors.affiliation: Microbial Physiology and ‡Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen , Nijenborgh 7, 9747 AG Groningen, The Netherlands.
authors.forename: Xiangfeng
authors.initials: X
authors.lastname: Meng
authors.affiliation: Microbial Physiology and ‡Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen , Nijenborgh 7, 9747 AG Groningen, The Netherlands.
authors.forename: Justyna M
authors.initials: JM
authors.lastname: Dobruchowska
authors.affiliation: Microbial Physiology and ‡Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen , Nijenborgh 7, 9747 AG Groningen, The Netherlands.
authors.forename: Tjaard
authors.initials: T
authors.lastname: Pijning
authors.affiliation: Microbial Physiology and ‡Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen , Nijenborgh 7, 9747 AG Groningen, The Netherlands.
authors.forename: Gerrit J
authors.initials: GJ
authors.lastname: Gerwig
authors.affiliation: Microbial Physiology and ‡Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen , Nijenborgh 7, 9747 AG Groningen, The Netherlands.
authors.forename: Lubbert
authors.initials: L
authors.lastname: Dijkhuizen
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D005936:Glucans / Q000096:biosynthesis* / Q000737:chemistry*; D016695:Glycosyltransferases / Q000235:genetics / Q000378:metabolism*; D052200:Limosilactobacillus reuteri / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D015394:Molecular Structure; D016296:Mutagenesis; D009154:Mutation; D013395:Sucrose / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D005936:Glucans; D013395:Sucrose; D016695:Glycosyltransferases; C033837:alternansucrase
keywords: GTF180; Lactobacillus reuteri; enzyme mutation; glucansucrase; hyperbranched α-glucan; product specificity