2 RHAMNOGALACTURONIDE TETRASACCHARIDES ISOLATED FROM SEMI-RETTED FLAXFIBERS ARE SIGNALING MOLECULES IN RUBUS-FRUTICOSUS L. CELLS

Water extraction of semi-retted flax (Linum usitatissimum L.) fiber bu ndles yielded a mixture of pectic oligosaccharides and two acidic rham nogalacturonide tetrasaccharides that were separated by size-exclusion chromatography. One- and two-dimensional nuclear magnetic resonance s tudies and fast atom bombardment-mass spectrometry experiments indicat ed that the two tetrasaccharides have a common primary structure, i.e. alpha-D-Delta ap(1-->4)-alpha-D-GalpA-(1-->2)-L-alpha,beta-Rhap, with a rhamnopyranose as terminal reducing end, and a 4-deoxy-beta-L-threo -hex-4-eno-pyranosiduronic acid at the nonreducing end. However, the t wo tetrasaccharides differ by an acetyl group located at the O-3 posit ion of the internal galacturonic acid residue. These two tetrasacchari des induce the activation of D-glycohydrolases of Rubus fructicosus L. cells or protoplasts within minutes.