Synthesis of New Hyperbranched α-Glucans From Sucrose by Lactobacillus Reuteri 180 Glucansucrase Mutants

J Agric Food Chem. 2016 Jan 20;64(2):433-42. doi: 10.1021/acs.jafc.5b05161. Epub 2016 Jan 8.

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.

Keywords: GTF180; Lactobacillus reuteri; enzyme mutation; glucansucrase; hyperbranched α-glucan; product specificity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Glucans / biosynthesis*
  • Glucans / chemistry*
  • Glycosyltransferases / genetics
  • Glycosyltransferases / metabolism*
  • Lactobacillus reuteri / enzymology*
  • Lactobacillus reuteri / genetics
  • Lactobacillus reuteri / metabolism
  • Molecular Structure
  • Mutagenesis
  • Mutation
  • Sucrose / metabolism*

Substances

  • Bacterial Proteins
  • Glucans
  • Sucrose
  • Glycosyltransferases
  • alternansucrase