Carbohydrate structures of three novel phosphoinositol-containing sphingolipids from the yeast Histoplasma capsulatum

From the yeast phase of the human pathogen Histoplasma capsulatum, three novel glycolipids were isolated, shown to react with sera from histoplasmosis patients, and partially characterized: compound V, ceramide-P-inositol-[mannose2]; compound VI, ceramide-P-inositol-[mannose2, galactose]; compound VIII, an isomer of compound VI [Barr, K., & Lester, R.L. (1984) Biochemistry (preceding paper in this issue)]. Ammonolysis of these lipids has yielded all the carbohydrate (oligosaccharides V, VI, and VIII) as novel, intact oligosaccharides suitable for characterization. Anomeric configurations were determined by specific glycosidase digestion and by the stability of peracetylated saccharides to CrO3 oxidation. Linkages were established by methylation analysis. These experiments yielded the following structural assignments: (formula; see text) The occurrence of galactofuranose is novel for glycosphingolipids, and it is noteworthy that compound VI is immunoreactive.