Glucosylation of raffinose via alternansucrase acceptor reactions |
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Authors: | Gregory L Côté Christopher A Dunlap |
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Institution: | a Bioproducts and Biocatalysis Research Unit, National Center for Agricultural Utilization Research, Agricultural Research Service, United States Department of Agriculture, 1815 N. University St., Peoria, IL 61604, USA†Mention of trade names or commercial products is solely for the purpose of providing specific information, and does not imply recommendation or endorsement by the US Department of Agriculture.† b Crop Bioprotection Research Unit, National Center for Agricultural Utilization Research, Agricultural Research Service, United States Department of Agriculture, 1815 N. University St., Peoria, IL 61604, USA c New Crops and Processing Technology Research Unit, National Center for Agricultural Utilization Research, Agricultural Research Service, United States Department of Agriculture, 1815 N. University St., Peoria, IL 61604, USA |
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Abstract: | The glucansucrase known as alternansucrase EC 2.4.1.140] can transfer glucosyl units from sucrose to raffinose to give good yields of oligosaccharides, which may serve as prebiotics. The main products were the tetrasaccharides α-d-Glcp-(1→3)-α-d-Galp-(1→6)-α-d-Glcp-(1↔2)-β-d-Fruf and α-d-Glcp-(1→4)-α-d-Galp-(1→6)-α-d-Glcp-(1↔2)-β-d-Fruf in ratios ranging from 4:1 to 9:1, along with lesser amounts of α-d-Glcp-(1→6)-α-d-Galp-(1→6)-α-d-Glcp-(1↔2)-β-d-Fruf. Ten unusual pentasaccharide structures were isolated. Three of these arose from glucosylation of the major tetrasaccharide product, two each from the minor tetrasaccharides, and three were the result of glucosylations of the fructose acceptor product leucrose or isomaltulose. The major pentasaccharide product arose from glucosylation of the major tetrasaccharide at position 4 of the fructofuranosyl unit, to give a subunit structure analogous to that of maltulose. A number of hexasaccharides and higher oligosaccharides were also produced. Unlike alternansucrase, dextransucrase EC 2.4.1.5] gave only a single tetrasaccharide product in low yield, and no significant amounts of higher oligosaccharides. The tetrasaccharide structure from dextransucrase was found to be α-d-Glcp-(1→4)-α-d-Galp-(1→6)-α-d-Glcp-(1↔2)-β-d-Fruf, which is at odds with the previously published structure. |
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Keywords: | Raffinose Oligosaccharides Alternansucrase Prebiotics Dextransucrase |
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