Mapping sugar beet pectin acetylation pattern.
Homogalacturonan-derived partly methylated and/or acetylated oligogalacturonates were recovered after enzymatic hydrolysis (endo-polygalacturonase+pectin methyl esterase+side-chain degrading enzymes) of sugar beet pectin followed by anion-exchange and size exclusion chromatography. Around 90% of the GalA and 75% of the acetyl groups present in the initial sugar beet pectin were recovered as homogalacturonan-derived oligogalacturonates, the remaining GalA and acetyl belonging to rhamnogalacturonic regions. Around 50% of the acetyl groups present in sugar beet homogalacturonans were recovered as partly methylated and/or acetylated oligogalacturonates of degree of polymerisation 5 whose structures were determined by electrospray ionization ion trap mass spectrometry (ESI-IT-MSn). 2-O-acetyl- and 3-O-acetyl-GalA were detected in roughly similar amounts but 2,3-di-O-acetylation was absent. Methyl-esterified GalA residues occurred mainly upstream 2-O-acetyl GalA. Oligogalacturonates containing GalA residues that are at once methyl- and acetyl-esterified were recovered in very limited amounts. A tentative mapping of the distribution of acetyl and methyl esters within sugar beet homogalacturonans is proposed. Unsubstituted GalA residues are likely to be present in limited amounts (approximately 10% of total GalA residues), due to the fact that methyl and acetyl groups are assumed to be most often not carried by the same residues.
Ralet
Marie-Christine
MC
Unité Biopolymères, Interactions, Assemblages, INRA, Rue de la Géraudière, B.P. 71627, F-44316 Nantes Cedex 3, France. ralet@nantes.inra.fr
Cabrera
Juan Carlos
JC
Bonnin
Estelle
E
Quéméner
Bernard
B
Hellìn
Pilar
P
Thibault
Jean-François
JF
D000107:Acetylation; D027461:Beta vulgaris / Q000737:chemistry*; D002240:Carbohydrate Sequence; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D006868:Hydrolysis; D007700:Kinetics; D009844:Oligosaccharides / Q000737:chemistry* / Q000302:isolation & purification; D010368:Pectins / Q000737:chemistry*; D014783:Viscosity
D009844:Oligosaccharides; D010368:Pectins