Structural characterization of the pectic polysaccharide, rhamnogalacturonan-II

Area of Science:

• Plant Biochemistry
• Carbohydrate Chemistry
• Structural Biology

Background:

• Rhamnogalacturonan-II (RG-II) is a complex pectic polysaccharide found in plant cell walls.
• Understanding RG-II structure is crucial for deciphering cell wall assembly and function.
• Previous studies have identified key oligosaccharide fragments within RG-II.

Purpose of the Study:

• To isolate and determine the structure of an octasaccharide released from sycamore cell wall RG-II.
• To investigate the O-acetylation patterns of the isolated octasaccharide and a related heptasaccharide.
• To contribute to the detailed structural elucidation of RG-II.

Main Methods:

• Selective acid hydrolysis to release the octasaccharide.
• Gel-permeation and high-performance anion-exchange chromatography for purification.
• Electrospray ionization tandem mass spectrometry (ESMSMS) for O-acetyl group localization.

Main Results:

• An octasaccharide (1) was purified from sycamore RG-II.
• Octasaccharide 1 contains a terminal arabinofuranosyl residue linked to a previously identified aceric acid-containing heptasaccharide (2).
• Both saccharides were found to be mono- or di-O-acetylated, with acetyl groups located on specific residues.

Conclusions:

• The study provides the detailed structure of a novel octasaccharide fragment of RG-II.
• The localization of O-acetyl groups offers insights into the modification of RG-II structures in sycamore cell walls.
• This work advances the understanding of complex plant cell wall polysaccharide architecture.