galactomannan and lignoceric-acid

Galactomannan is a characteristic polysaccharide of the human filamentous fungal pathogen Aspergillus fumigatus that can be used to diagnose invasive aspergillosis. In this study, we report the isolation of a galactomannan fraction associated to membrane preparations from A. fumigatus mycelium by a lipid anchor. Specific chemical and enzymatic degradations and mass spectrometry analysis showed that the lipid anchor is a glycosylphosphatidylinositol (GPI). The lipid part is an inositol phosphoceramide containing mainly C18-phytosphingosine and monohydroxylated lignoceric acid (2OH-C(24:0) fatty acid). GPI glycan is a tetramannose structure linked to a glucosamine residue: Manalpha1-2Manalpha1-2Manalpha1-6Manalpha1-4GlcN. The galactomannan polymer is linked to the GPI structure through the mannan chain. The GPI structure is a type 1, closely related to the one previously described for the GPI-anchored proteins of A. fumigatus. This is the first time that a fungal polysaccharide is shown to be GPI-anchored.

Topics: alpha-Mannosidase; Aspergillus fumigatus; Carbohydrates; Chromatography, Gas; Chromatography, Gel; Fabaceae; Fatty Acids; Galactose; Glucosamine; Glycosylphosphatidylinositols; Hydrolysis; Inositol; Lipid Metabolism; Lipids; Mannans; Mannose; Mass Spectrometry; Nitrous Acid; Polymers; Polysaccharides; Time Factors; Type C Phospholipases