title: Structural characterisation of xyloglucan secreted by suspension-cultured cells of Nicotiana plumbaginifolia.
abstract: Linkage analysis of a xyloglucan from the extracellular medium of suspension cultures of Nicotiana plumbaginifolia showed mostly 4-Glcp and 4,6-Glcp, terminal Xylp and 2-Xylp, and terminal Araf, along with approximately 10% (w/w) O-acetyl groups, equivalent to approximately 0.28 mol acetyl per mol of glycosyl residue. Methylation with methyl trifluoromethanesulfonate under neutral conditions, followed by re-methylation with CD3I under basic conditions, and conversion into partially methylated alditol acetates showed that O-acetyl groups were primarily attached to C-6 of approximately 44% of the 4-Glcp backbone not substituted with Xylp residues and to C-5 of approximately 15% of the terminal Araf residues. These positions of the O-acetyl groups were confirmed by 1H-NMR. Oligosaccharides generated by digestion of native xyloglucan with endo-(1-->4)-beta-glucanase were separated by a combination of gel-filtration chromatography and anion-exchange HPLC, and analysed by glycosyl linkage analysis and by electrospray ionisation-mass spectrometry (ESI-MS). The major oligosaccharide subunits were Glc4Xyl2 and Glc5Xyl2, of which 50-60% are substituted with one terminal Araf residue attached to O-2 of a Xylp residue, and a further 20-25% are substituted with two terminal Araf residues attached to O-2 of the Xylp residues. ESI-MS showed that many of the oligosaccharide subunits carried one, two, and, occasionally three O-acetyl groups.
authors.affiliation: Cooperative Research Centre for industrial Plant Biopolymers, School of Botany, University of Melbourne, Victoria, Australia.
authors.forename: I M
authors.initials: IM
authors.lastname: Sims
authors.forename: S L
authors.initials: SL
authors.lastname: Munro
authors.forename: G
authors.initials: G
authors.lastname: Currie
authors.forename: D
authors.initials: D
authors.lastname: Craik
authors.forename: A
authors.initials: A
authors.lastname: Bacic
mesh_terms: D000107:Acetylation; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002473:Cell Wall / Q000737:chemistry; D002478:Cells, Cultured; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D005936:Glucans; D005959:Glucosidases / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009005:Monosaccharides / Q000032:analysis; D009844:Oligosaccharides / Q000032:analysis / Q000737:chemistry; D010947:Plants, Toxic; D011134:Polysaccharides / Q000737:chemistry* / Q000302:isolation & purification; D014026:Nicotiana / Q000737:chemistry*; D014990:Xylans
chemical_list: D005936:Glucans; D009005:Monosaccharides; D009844:Oligosaccharides; D011134:Polysaccharides; D014990:Xylans; C029353:xyloglucan; D005959:Glucosidases; D006026:Glycoside Hydrolases; C019713:alpha-N-arabinofuranosidase