Glucuronic acid directly linked to galacturonic acid in the rhamnogalacturonan backbone of beet pectins. |
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| Authors: | C M Renard M J Crépeau J F Thibault |
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| Affiliation: | Unité de Recherches sur de Polysaccharides, leurs Organisations et Interactions, Institut National de la Recherches Agronomique, Centre de Recherche Agro-Alimentaire de Nantes, France. crenard@rennes.inra.fr |
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| Abstract: | Sugar-beet pulp was de-esterified and submitted to 72 h hydrolysis by 0.1 M HCl at 80 degrees C. Oligomers containing a single glucuronic acid (GlcA) moiety in addition to n(>/= 2) repeats of the dimer -->4)-alpha-D-GalpA-(1-->2)-alpha-L-Rhap-(1--> were isolated from the hydrolysate by ion-exchange and gel-permeation. Glycosyl linkage composition analysis and 1H NMR studies indicated that the GlcA was attached to O-3 of a galacturonic acid (GalA) residue, as shown for the two pentamers beta-D-GlcpA-(1-->3)-alpha-D-GalpA-(1-->2)-alpha-L-Rhap-(1-->4)-alpha-D-GalpA-(1-->2)-L-Rhap and alpha-D-GalpA-(1-->2)-alpha-L-Rhap-(1-->4)-[beta-D-GlcpA-(1-->3)]-alpha-D-GalpA-(1-->2)-L-Rhap. Substitution by GlcA was estimated as occurring on one GalA residue out of 72 in the rhamnogalacturonan fraction of the backbone of beet pectins. |
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