Abstract
A series of heteropalysaccharides were isolated from the delipidated cell wall fraction of Spirulina maxima, by successive extractions with cold and hot water, and then with cold and hot alkali. These polysaccharides had similar carbohydrate compositions, containing L-rhamnose as the main component, and D-galactose, D-glucose, D-mannose and D-glucuronic acid, although the proportions of these com- ponents appeared to vary according to the extraction conditions employed. Methylation and Smith degradation studies indicated that they had essentially similar structural features, containing a backbone chain of α- (1→3) -linked L-rhamnose residues, some of which were substituted with other sugar residues at the C-2 and C-4 positions. The side-chains were shown to consist of (1→3) -, and (1→4) -linked D-glucose and D-mannose residues, and (1→4) -linked D-galactose residues; most of the D-glucuronic acid residues were found to be located at the terminal ends. A highly branched glycogen-type α-D-glucan was also isolated from the water extract of the crude cell wall preparation. Methylation and gel filtration studies, involving the action of debranching enzymes, showed that the lengths of the α- (1→4) -linked unit chains of the D-glucose residues were distributed in the range of DP 3 to 14. The insoluble residues remaining after hot alkali treatment of the cell wall contained D-glucosamine and muramic acid, in addition to several kinds of amino acids, suggesting the presence of a peptidoglycan, similar to that of bacterial cell walls.
