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Glucan synthesis in the genus Lactobacillus: Isolation and characterization of glucansucrase genes, enzymes and glucan products from six different strains

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Author: Kralj, S. · Geel-Schutten, G.H. van · Dondorff, M.M.G. · Kirsanovs, S. · Maarel, M.J.E.C. van der · Dijkhuizen, L.
Type:article
Date:2004
Institution: TNO Voeding Centraal Instituut voor Voedingsonderzoek TNO
Source:Microbiology, 11, 150, 3681-3690
Identifier: 238069
doi: doi:10.1099/mic.0.27321-0
Keywords: Nutrition · Food technology · Amino acid · Bacterial enzyme · Dextransucrase · Glucan · Glucosyltransferase · Sucrase · Amino terminal sequence · Bacterial strain · Binding site · Carbohydrate synthesis · Controlled study · Enzyme analysis · Enzyme isolation · Gene isolation · Gene sequence · Genetic analysis · Lactobacillus · Lactobacillus fermentum · Lactobacillus reuteri · Lactobacillus sakei · Nonhuman · Nucleotide sequence · Priority journal · Protein structure · Amino Acid Motifs · Bacterial Proteins · Binding Sites · Catalytic Domain · Cloning, Molecular · DNA, Bacterial · Escherichia coli · Genes, Bacterial · Glucans · Glucosyltransferases · Glycosyltransferases · Lactobacillus · Molecular Sequence Data · Phylogeny · Protein Sorting Signals · Protein Structure, Tertiary · Recombinant Proteins · Repetitive Sequences, Amino Acid · Sequence Analysis, DNA · Sequence Homology, Amino Acid · Sucrase · Lactobacillus · Lactobacillus fermentum · Lactobacillus parabuchneri · Lactobacillus reuteri · Lactobacillus sakei · Leuconostoc · Streptococcus

Abstract

Members of the genera Streptococcus and Leuconostoc synthesize various α-glucans (dextran, alternan and mutan). In Lactobacillus, until now, the only glucosyltransferase (GTF) enzyme that has been characterized is gtfA of Lactobacillus reuteri 121, the first GTF enzyme synthesizing a glucan (reuteran) that contains mainly α-(1 → 4) linkages together with α-(1 → 6) and α-(1 → 4,6 linkages. Recently, partial sequences of glucansucrase genes were detected in other members of the genus Lactobacillus. This paper reports, for the first time, isolation and characterization of dextransucrase and mutansucrase genes and enzymes from various Lactobacillus species and the characterization of the glucan products synthesized, which mainly have α-(1 → 6)- and α-(1 → 3)-glucosidic linkages. The four GTF enzymes characterized from three different Lb. reuteri strains are highly similar at the amino acid level, and consequently their protein structures are very alike. Interestingly, these four Lb. reuteri GTFs have relatively large N-terminal variable regions, containing RDV repeats, and relatively short putative glucan-binding domains with conserved and less-conserved YG-repeating units. The three other GTF enzymes, isolated from Lactobacillus sakei, Lactobacillus fermentum and Lactobacillus parabuchneri, contain smaller variable regions and larger putative glucan-binding domains compared to the Lb. reuteri GTF enzymes. © 2004 SGM.