Pectic polysaccharides from xylem-differentiating zone of Cryptomeria japonica

Abstract

Pectin was extracted from the cell walls of xylem-differentiating zones of sugi ( Cryptomeria japonica) with the chelating agent, trans-1,2-cyclohexanediamine- N, N, N′, N′-tetraacetic acid at 20° and Na 2CO 3 solution at 1° and 20°. The extracted pectin fractions were purified by anion-exchange chromatography and digested with pure endo-polygalacturonase from Aspergillus niger. The hydrolysates were then fractionated by gel permeation chromatography into three or four fractions. Sugar composition and glycosyl linkage composition analyses of each fraction showed that the void volume fractions contained 2- and 2,4-linked rhamnosyl, 5-linked arabinosyl, terminal galactosyl and 4-linked galacturonic acid residues, indicating that they were rhamnogalacturonan I. The fractions obtained from the included volume had rare sugar residues, such as apiosyl, 2-O- methyl- l-fucosyl , traces of 3-O- methyl- l-fucosyl , 2-O- methyl- d-xylosyl residues aceric acid and thiobarbituric acid assay-positive sugar residues, showing that these fractions contained rhamnogalacturonan II-like polysaccharides. Several linear oligosaccharides composed of (1 → 4)-linked α- d-galacturonic acid residues were purified from the lowest M r regions and some oligogalacturonides were characterized by methylation analysis, FAB-mass spectrometry and NMR.