Hybrid reuteransucrase enzymes reveal regions important for glucosidic linkage specificity and the transglucosylation/hydrolysis ratio

The reuteransucrase enzymes of Lactobacillus reuteri strain 121 (GTFA) and L. reuteri strain ATCC 55730 (GTFO) convert sucrose into alpha-d-glucans (labelled reuterans) with mainly alpha-(1→4) glucosidic linkages (50% and 70%, respectively), plus alpha-(1→6) linkages. In the present study, we report a detailed analysis of various hybrid GTFA/O...

Rational transformation of Lactobacillus reuteri 121 reuteransucrase into a dextransucrase

Glucansucrase or glucosyltransferase (GTF) enzymes of lactic acid bacteria display high sequence similarity but catalyze synthesis of different α-glucans (e.g., dextran, mutan, alternan, and reuteran) from sucrose. The variations in glucosidic linkage specificity observed in products of different glucansucrase enzymes appear to be based on...

The Aspergillus niger MADS-box transcription factor RlmA is required for cell wall reinforcement in response to cell wall stress

In Aspergillus niger, the genes coding for glutamine:fructose-6-phosphate amidotransferase (gfaA) and α-1,3-glucan synthase (agsA) are induced in response to cell wall stress. In silico analysis of the promoter region of the two genes revealed the presence of putative DNA binding sites for transcription factors involved in stress responses,...

Expression of agsA, one of five 1,3-α-d-glucan synthase-encoding genes in Aspergillus niger, is induced in response to cell wall stress

1,3-α-d-Glucan is an important component of the cell wall of filamentous fungi. We have identified a family of five 1,3-α-d-glucan synthase-encoding genes in Aspergillus niger. The agsA gene was sequenced and the predicted protein sequence indicated that the overall domain structure of 1,3-α-d-glucan synthases is conserved in fungi. Using RT-PCR...

Highly hydrolytic reuteransucrase from probiotic Lactobacillus reuteri strain ATCC 55730

Lactobacillus reuteri strain ATCC 55730 (LB BIO) was isolated as a pure culture from a Reuteri tablet purchased from the BioGaia company. This probiotic strain produces a soluble glucan (reuteran), in which the majority of the linkages are of the alpha-(1→4) glucosidic type (∼70%). This reuteran also contains alpha-(1→6)-linked glucosyl units...

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

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...

Safety evaluation of an α-cyclodextrin glycosyltranferase preparation

Alpha-cyclodextrin glucosyltransferase (α-CGTase, EC 2.4.1.19) is an amylolytic enzyme used for the production of α-cyclodextrin (α-CD), a novel, soluble dietary fiber, from food-grade starch. The safety of an α-CGTase preparation obtained by batch fermentation from a recombinant strain of Escherichia coli K12 harboring the α-CGTase gene from...

Efficient screening methods for glucosyltransferase genes in Lactobacillus strains

Limited information is available about homopolysaccharide synthesis in the genus Lactobacillus. Using efficient screening techniques, extracellular glucosyltransferase (GTF) enzyme activity, resulting in α-glucan synthesis from sucrose, was detected in various lactobacilli. PCR with degenerate primers based on homologous boxes of known...

Localization of synthesis of β1,6-glucan in Saccharomyces cerevisiae

β1,6-Glucan is a key component of the yeast cell wall, interconnecting cell wall proteins, β1,3-glucan, and chitin. It has been postulated that the synthesis of β1,6-glucan begins in the endoplasmic reticulum with the formation of protein-bound primer structures and that these primer structures are extended in the Golgi complex by two putative...