Title: Glucosylation of Raffinose via Glucansucrase Acceptor Reactions Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: August 20, 2009
Publication Date: August 20, 2009
Citation: Cote, G.L., Dunlap, C.A., Vermillion, K. 2009. Glucosylation of raffinose via glucansucrase acceptor reactions [abstract]. American Chemical Society. Paper ID 1271382. Technical Abstract: The trisaccharide raffinose (a-D-galactopyranosyl-(1-6)-a-D-glucopyranosyl-(1-2)-ß-D-fructofuranoside) occurs in the seeds of many plants, especially legumes, along with its galactosylated homologues stachyose and verbascose. The glucansucrase known as alternansucrase [EC 18.104.22.168] transfers glucosyl units from sucrose to raffinose to give good yields of oligosaccharides which may serve as prebiotics. The main products were the tetrasaccharides a-D-glucopyranosyl-(1-3)-a-D-galactopyranosyl-(1-6)-a-D-glucopyranosyl-(1-2)-ß-D-fructofuranoside and a-D-glucopyranosyl-(1'4)-a-D-galactopyranosyl-(1'6)-a-D-glucopyranosyl-(1-2)-ß-D-fructofuranoside in ratios ranging from 4:1 to 9:1, along with lesser amounts of a-D-glucopyranosyl-(1-6)-a-D-galactopyranosyl-(1-6)-a-D-glucopyranosyl-(1-2)-ß-D-fructofuranoside. 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 products leucrose or isomaltulose. The major pentasaccharide products arose from glucosylation of the major tetrasaccharides at position 4 of the fructofuranosyl unit. A number of hexasaccharides and higher oligosaccharides were also produced but their structures were not determined. The yields of oligosaccharides were much higher using alternansucrase than with dextransucrase [EC 22.214.171.124]. The main product of the dextransucrase-catalyzed glucosylation was a-D-glucopyranosyl-(1-4)-a-D-galactopyranosyl-(1-6)-a-D-glucopyranosyl-(1-2)-ß-D-fructofuranoside, which is at odds with the previously published structure.