Rhamnogalacturonan II from cell walls of Cryptomeria japonica

Abstract

Rhamnogalacturonan II (RG-II) was isolated from cell walls of sugi ( Cryptomeria japonica). The oligosaccharides which could not be generated from sycamore ( Acer psuedoplatanus, angiosperm) RG-II were produced from sugi RG-II by lithium treatment. The structure of sugi RG-II is supposed to be partially different from that of sycamore RG-II. The pectic polysaccharides isolated from cell walls of xylem-differentiating zones of sugi (Cryptomeria japononica) were degraded with endo- α-(1 → 4)-polygalacturonase and the polysaccharides, composed mainly of rhamnogalacturonan II (RG-II), were obtained from the degradation products. These polysaccharides consisted of rhamnosyl, fucosyl, arabinosyl, xylosyl, galactosyl, glucosyl, galacturonic acid, glucuronic acid and the characteristic sugars of RG-II, namely, 2- O-methylfucose, 2- O-methylxylose, apiose, aceric acid and thiobarbituric acid assay-positive glycosyl {probably, 3-deoxy- d- manno-2-octulosonic acid (Kdo) and 3-deoxy- d- lyxo-heptulosaric acid (Dha)}. The polysaccharides contained the glycosyl residues of RG-II, besides small amounts of the glycosyl linkages of RG-I. The RG-II was structurally analysed by partial acid hydrolysis and lithium treatment in ethylenediamine. The glycosyl sequences of three compounds generated by partial hydrolysis were not identical to the partial structure of the sycamore ( Acer pseudoplatanus) RG-I and RG-II structures previously proposed by Albersheim et al. Furthermore, five novel glycosyl sequences were detected in the products from lithium treatment. The results suggest that the structure of sugi RG-II is somewhat different from that of sycamore RG-II.