title: 4,3-α-Glucanotransferase, a novel reaction specificity in glycoside hydrolase family 70 and clan GH-H.
abstract: Lactic acid bacteria possess a diversity of glucansucrase (GS) enzymes that belong to glycoside hydrolase family 70 (GH70) and convert sucrose into α-glucan polysaccharides with (α1 → 2)-, (α1 → 3)-, (α1 → 4)- and/or (α1 → 6)-glycosidic bonds. In recent years 3 novel subfamilies of GH70 enzymes, inactive on sucrose but using maltodextrins/starch as substrates, have been established (e.g. GtfB of Lactobacillus reuteri 121). Compared to the broad linkage specificity found in GSs, all GH70 starch-acting enzymes characterized so far possess 4,6-α-glucanotransferase activity, cleaving (α1 → 4)-linkages and synthesizing new (α1 → 6)-linkages. In this work a gene encoding a putative GH70 family enzyme was identified in the genome of Lactobacillus fermentum NCC 2970, displaying high sequence identity with L. reuteri 121 GtfB 4,6-α-glucanotransferase, but also with unique variations in some substrate-binding residues of GSs. Characterization of this L. fermentum GtfB and its products revealed that it acts as a 4,3-α-glucanotransferase, converting amylose into a new type of α-glucan with alternating (α1 → 3)/(α 1 → 4)-linkages and with (α1 → 3,4) branching points. The discovery of this novel reaction specificity in GH70 family and clan GH-H expands the range of α-glucans that can be synthesized and allows the identification of key positions governing the linkage specificity within the active site of the GtfB-like GH70 subfamily of enzymes.
authors.affiliation: Microbial Physiology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands.
authors.forename: Joana
authors.initials: J
authors.lastname: Gangoiti
authors.affiliation: Microbial Physiology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands.
authors.forename: Sander S
authors.initials: SS
authors.lastname: van Leeuwen
authors.affiliation: Microbial Physiology, 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: Nestlé Research Center, Vers-Chez-Les-Blanc, Lausanne, Switzerland.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Duboux
authors.affiliation: Nestlé Research Center, Vers-Chez-Les-Blanc, Lausanne, Switzerland.
authors.forename: Christina
authors.initials: C
authors.lastname: Vafiadi
authors.affiliation: 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, 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 / Q000737:chemistry / Q000378:metabolism*; D019143:Evolution, Molecular; D005936:Glucans / Q000737:chemistry / Q000378:metabolism; D005964:Glucosyltransferases / Q000737:chemistry / Q000378:metabolism*; D006004:Glycogen Debranching Enzyme System / Q000737:chemistry / Q000378:metabolism*; D006027:Glycosides / Q000737:chemistry / Q000378:metabolism; D052197:Limosilactobacillus fermentum / Q000201:enzymology*; D052200:Limosilactobacillus reuteri / Q000201:enzymology*; D010802:Phylogeny; D011134:Polysaccharides / Q000737:chemistry / Q000378:metabolism; D013379:Substrate Specificity; D013395:Sucrose / Q000737:chemistry / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D005936:Glucans; D006004:Glycogen Debranching Enzyme System; D006027:Glycosides; D011134:Polysaccharides; D013395:Sucrose; C008315:maltodextrin; C036655:1,3-alpha-D-glucan synthase; D005964:Glucosyltransferases; C020569:4 alpha-glucanotransferase