title: The occurrence of internal (1 --> 5)-linked arabinofuranose and arabinopyranose residues in arabinogalactan side chains from soybean pectic substances.
abstract: CDTA-extractable soybean pectic substances were subjected to enzymatic digestion with arabinogalactan degrading enzymes yielding a resistant polymeric pectic backbone and arabino-, galacto-, and arabinogalacto-oligomers. The complex digest was fractionated using size-exclusion chromatography. Monosaccharide composition analysis, HPAEC fractionation and MALDI-TOF MS analysis of the resulting fractions showed that each contained a mixture of oligosaccharides of essentially the same degree of polymerisation, composed of only arabinose and galactose. MALDI-TOF MS analysis was used for molecular mass screening of oligosaccharides in underivatised HPAEC fractions. The monosaccharide sequence and the branching pattern of oligosaccharides (degree of polymerisation from 4 to 8) were determined using linkage analysis and ES-CID tandem MS analysis of the per-O-methylated oligosaccharides in each of the HPAEC fractions. These analyses indicated the presence of common linear (1 --> 4)-linked galacto-oligosaccharides, and both linear and branched arabino-oligosaccharides. In addition, the results unambiguously showed the presence of oligosaccharides containing (1 --> 4)-linked galactose residues bearing an arabinopyranose residue as the non-reducing terminal residue, and a mixture of linear oligosaccharides constructed of (1 --> 4)-linked galactose residues interspersed with an internal (1 --> 5)-linked arabinofuranose residue. The consequences of these two new structural features of pectic arabinogalactan side chains are discussed.
authors.affiliation: Department of Food Technology and Nutritional Sciences, Wageningen University, The Netherlands.
authors.forename: M M
authors.initials: MM
authors.lastname: Huisman
authors.forename: L P
authors.initials: LP
authors.lastname: Brül
authors.forename: J E
authors.initials: JE
authors.lastname: Thomas-Oates
authors.forename: J
authors.initials: J
authors.lastname: Haverkamp
authors.forename: H A
authors.initials: HA
authors.lastname: Schols
authors.forename: A G
authors.initials: AG
authors.lastname: Voragen
mesh_terms: D001089:Arabinose / Q000737:chemistry; D002236:Carbohydrate Conformation; D002614:Chelating Agents; D002850:Chromatography, Gel; D004492:Edetic Acid / Q000031:analogs & derivatives*; D005685:Galactans / Q000737:chemistry*; D006026:Glycoside Hydrolases / Q000378:metabolism; D008958:Models, Molecular; D009844:Oligosaccharides / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D010368:Pectins / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D013025:Glycine max / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D002614:Chelating Agents; D005685:Galactans; D009844:Oligosaccharides; C005390:CDTA; D010368:Pectins; D004492:Edetic Acid; D001089:Arabinose; D006026:Glycoside Hydrolases; C005653:arabinogalactan