RHAMNOGALACTURONAN-I FROM XYLEM DIFFERENTIATING ZONES OF CRYPTOMERIA-JAPONICA

Rhamnogalacturonan I (RG-I) was isolated from the pectin of the cell w all of xylem differentiating zones of sugi (Cryptomeria japonica D. Do n, gymnosperm) by digesting with endo-alpha-1,4-polygalacturonase foll owed by gel-permeation chromatography. Structure of RG-I was character ized by glycosyl composition and glycosyl linkage analyses, partial ac id hydrolysis, and lithium (Li)-treatment in ethylenediamine. The olig osaccharides produced by partial acid hydrolysis showed the backbone o f RG-I to be a disaccharide repeating unit of --> 4)-alpha-D-GalpA-(1 --> ,2)-alpha-L-Rhap-(1 -->. Arabinan and oligogalactosyl side chains were attached at O-4 of rhamnosyl residues of the backbone. Glycosyl c omposition and glycosyl linkage analyses suggested that the structures and/or the distribution of the arabinan sidechains of sugi RG-I were different from those of sycamore (angiosperm) RG-I. (C) 1997 Elsevier Science Ltd. All rights reserved.