Biochemical characterization of two GH70 family 4,6-α-glucanotransferases with distinct product specificity from Lactobacillus aviarius subsp. aviarius DSM 20655

Xiangfeng Meng, Joana Gangoiti, Niels de Kok, Sander S van Leeuwen, Tjaard Pijning, Lubbert Dijkhuizen

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Abstract

Nine GtfB-like 4,6-α-glucanotransferases (4,6-α-GTs) (represented by GtfX of L. aviarius subsp. aviarius DSM 20655) were identified to show distinct characteristics in conserved motifs I-IV. In particular, the "fingerprint" Tyr in motif III of these nine GtfB-type 4,6-α-GTs was found to be replaced by a Trp. In L. aviarius subsp. aviarius DSM20655, a second GtfB-like protein (GtfY), containing the canonical GtfB Tyr residue in motif III, was located directly upstream of GtfX. Biochemical characterization revealed that both GtfX and GtfY showed GtfB-like 4,6-α-GT activity, cleaving (α1→4) linkages and catalyzing the synthesis of (α1→6) linkages. Nonetheless, they differ in product specificity; GtfY only synthesizes consecutive (α1→6) linkages, yielding linear α-glucan products, but GtfX catalyzes the synthesis of (α1→6) linkages predominantly at branch points (22%) rather than in linear segments (10%). The highly branched α-glucan produced by GtfX from amylose V is resistant to digestion by α-amylase, offering great potential as dietary fibers.

Original languageEnglish
Article numberj.foodchem.2018.01.154
Pages (from-to)236-246
Number of pages11
JournalFood Chemistry
Volume253
DOIs
Publication statusPublished - 1-Jul-2018

Keywords

  • alpha-glucan
  • 4,6-alpha-Glucanotransferase
  • Family GH70
  • Lactic acid bacteria
  • Glucansucrase
  • Polysaccharides
  • LACTIC-ACID BACTERIA
  • STRUCTURAL-CHARACTERIZATION
  • MOLECULAR CHARACTERIZATION
  • GLUCANSUCRASE GTF180
  • ACTIVE-SITE
  • REUTERI 121
  • ENZYMES
  • GLUCAN
  • STARCH
  • GTFB

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