Characterization of a 4,6-a-glucanotransferase from Lactobacillus reuteri E81 and production of malto-oligosaccharides with immune-modulatory roles

Authors: ISPIRLI, HÜMEYRA - Yildiz Technical University; SIMSEK, ÖMER - Pamukkale University; Skory, Christopher - Chris; SAGDIC, OSMAN - Yildiz Technical University; DERTLI, ENES - Bayburt University

Submitted to: International Journal of Biological Macromolecules
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/3/2018
Publication Date: 12/5/2018
Citation: Ispirli, H., Simsek, Ö., Skory, C.D., Sagdic, O., Dertli, E. 2018. Characterization of a 4,6-a-glucanotransferase from Lactobacillus reuteri E81 and production of malto-oligosaccharides with immune-modulatory roles. International Journal of Biological Macromolecules. 124:1213-1219. https://doi.org/10.1016/j.ijbiomac.2018.12.050.
DOI: https://doi.org/10.1016/j.ijbiomac.2018.12.050

Interpretive Summary: Certain bacteria used in fermented foods produce enzymes called glucansucrases that synthesize polymers of glucose called glucans, from cane or beet sugars, which contribute to the quality of many types of these foods. These same enzymes are also capable of producing short sugar chains, called oligosaccharides that are used as prebiotics for improved intestinal health. In this study, we identified a novel glucansucrase-like enzyme, called GtfB-E81, from a Lactobacillus bacterium isolated from a traditional Turkish sourdough and showed that it produces glucans in a unique manner. As a result, it is possible to synthesize new oligosaccharides for prebiotic applications that were not possible with traditional glucansucrase enzymes. Several of these new oligosaccharides were shown to illicit an anti-inflammatory immune response in cell cultures. These findings show the potential of these types of enzymes with synthesis of novel glucans and oligosaccharides with potentially important roles in the food industry as food stabilizing agents or prebiotics.

Technical Abstract: A wide number of Lactic Acid Bacteria (LAB) species produce a-glucans with their ability to synthesize glucansucrases (GS) which use sucrose as substrate for the glucan production. Recently another group of enzymes in LAB gained special interest for their ability to produce a-glucans targeting the substrates containing a1-4-linkages and synthesizing new (a1-6) or (a1-3)–linkages as a -glucanotransferases. In this study, a putative 4,6-a-glucanotransferase (GTFB) from sourdough isolate Lactobacillus reuteri E81 was identified and expressed in Escherichia coli. The biochemical characterization of the GTFB-E81 confirmed its function as it cleaved the a1-4-linkages in different substrates and produced new gluco-oligomers/polymers containing a1-6 linkages together with the a1-4-linkages detected by NMR analysis. GTFB-E81 produced malto-oligosaccharides targeting maltose and maltoheptaose as substrates with up to DP 8 detected by TLC and ESI-MS/MS analysis. The functional roles of these malto-oligosaccharides were determined by testing their immune-modulatory functions in HT29 cells and they triggered the production of anti-inflammatory 1L-4 and pro-inflammatory IL-12 cytokines.