Isolation and structural characterization of beta-D-glucosyluronic acid and 4-O-methyl beta-D-glucosyluronic acid-containing oligosaccharides from the cell-wall pectic polysaccharide, rhamnogalacturonan I.
Rhamnogalacturonan I (RG-I), a pectic polysaccharide isolated from the walls of suspension-cultured sycamore cells, was shown by glycosyl-residue composition analysis to contain D-glucosyluronic acid (GlcpA) residues (1 mol%) and 4-O-methyl-D-glucosyluronic acid (4-O-Me-GlcpA) residues (0.5 mol%). These monosaccharides were shown, by glycosyl-linkage analysis, to be present in RG-I as terminal nonreducing residues. The glycosyl sequences containing GlcpA and 4-O-Me-GlcpA were determined by structurally characterizing the acidic oligosaccharides released by partial acid hydrolysis of RG-I. Six acidic oligosaccharides were purified by semipreparative high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) and characterized by glycosyl-residue and glycosyl-linkage composition analyses, GLC-CIMS, GLC-EIMS, electrospray MS (ESMS), and 1H NMR spectroscopy. We propose that three of the acidic oligosaccharides characterized, 4-O-Me-beta-D-GlcpA-(1-->6)-D-Gal, beta-D-GlcpA-(1-->6)-D-Gal, and beta-D-GlcpA-(1-->4)-D-Gal, originate from the galactosyl-containing side chains of RG-I. The three other acidic oligosaccharides characterized, alpha-D-GalpA-(1-->2)-L-Rha, alpha-D-GalpA-(1-->2)-alpha-L-Rhap-(1-->4)-alpha-D-GalpA+ ++-(1-->2)-alpha-L-Rha, and alpha-D-GalpA-(1-->2)-alpha-L-Rhap-(1-->4)-alpha-D-GalpA+ ++-(1-->2)-alpha-L- Rhap-(1-->4)-alpha-D-GalpA-(1-->2)-alpha-L-Rha, were generated by partial hydrolysis of the RG-I backbone. No evidence was obtained for the presence of galactosyluronic acid in the side chains of RG-I.(ABSTRACT TRUNCATED AT 250 WORDS)
An
J
J
Complex Carbohydrate Research Center, University of Georgia, Athens 30602-4712.
O'Neill
M A
MA
Albersheim
P
P
Darvill
A G
AG
D002240:Carbohydrate Sequence; D002473:Cell Wall / Q000737:chemistry*; D005965:Glucuronates / Q000032:analysis*; D020723:Glucuronic Acid; D006027:Glycosides / Q000737:chemistry; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry / Q000302:isolation & purification; D010368:Pectins / Q000737:chemistry*; D014197:Trees / Q000737:chemistry*
D005965:Glucuronates; D006027:Glycosides; D009844:Oligosaccharides; C042491:rhamnogalacturonan I; C036035:4-O-methylglucuronic acid; D010368:Pectins; D020723:Glucuronic Acid