Composition of a methylated, acidic polysaccharide associated with coccoliths of Emiliania huxleyi (Lohmann) Kamptner

Abstract

The water-soluble, acidic polysaccharide isolated from the coccoliths of the alga Emiliania huxleyi (Lohmann) Kamptner contains residues of the following sugars: L-galactose, D-glucose, D-mannose, L-mannose, L-rhamnose, L-arabinose, D-ribose, D-xylose, 6-O-methyl-D-mannose, 6-O-methyl-L-mannose, 2,3-di-O-methyl-L-rhamnose, 3-O-methyl-D-xylose, and D-galacturonic acid. L-Mannose, 6-O-methyl-D-mannose, 6-O-methyl-L-mannose, and 2,3-di-O-methyl-L-rhamnose are novel constituents of a polysaccharide. In addition, the presence of sulphate groups was found. Galacturonic acid and sulphate in the polysaccharide bind Ca2+ ions apparently in a ratio of one mol of Ca2+ per mol of acidic residue. This feature is relevant for the proposed matrix function of the polysaccharide in the formation of the calcified cell-wall plates (coccoliths) of the alga.