Galactose-containing polysaccharides from the human pathogens Sporothrix schenckii and Ceratocystis stenoceras

Abstract

Galactose-containing polysaccharides from three strains of Sporothrix schenckii and one strain of Ceratocystis stenoceras were isolated, and their structures were paritally characterized by chemical analysis and 13C-nuclear magnetic resonance spectroscopy (13C-NMR). S. schenckii polysaccharide preparations from all strains were not precipitated by Fehling solution and contained galactomannan (or a mixture of galactan and galactomannan), amylose, and minor amounts of rhamnomannan. C. stenoceras polysaccharide contained galactomannan and a smaller proportion of amylose. Conventional chemical techniques and 13C-NMR spectroscopy showed that the structures of the two preparations were closely related. The core of the galactomannan consisted principally of nonreducing end units and 2-O-, 2,6-di-O-, and perhaps 2,3-di-O-substituted alpha-D-mannopyranosyl units. The core was substituted by beta-D-galactofuranosyl chains; the units are interlinked (1 leads to 6). 13C-NMR evidence shows that the alpha-D-mannopyranosyl units are substituted in the two positions by the beta-D-galactofuranosyl residues. Galactomannans present at the cell surface of S. schenckii represent other potential fungal antigens in addition to the already recognized rhamnomannans and their peptide complexes.