The opportunistic fungal pathogen Scedosporium prolificans: Carbohydrate epitopes of its glycoproteins

Isolated from the mycelium of Scedosporium prolificans were complex glycoproteins (RMP-Sp), with three structurally related components (HPSEC). RMP-Sp contained 35% protein and 62% carbohydrate with Rha, Ara, Man, Gal, Glc, and GlcNH2 in a 18:1:24:8:6:5 molar ratio. Methylation analysis showed mainly nonreducing end- of Galp (13%), nonreducing end- (9%), 2-O- (13%), and 3-O-subst. Rhap (7%), nonreducing end- (11%), 2-O- (10%), 3-O- (14%), and 2,6-di-O-subst. Manp units (13%). Mild reductive β-elimination of RMP-Sp gave α-l-Rhap-(1 → 2)-α-l-Rhap-(1 → 3)-α-l-Rhap-(1 → 3)-α-d-Manp-(1 → 2)-d-Man-ol, with Man-ol substituted at O-6 with β-d-Galp units, a related pentasaccharide lacking β-d-Galp units, and β-d-Galp-(1 → 6)-[α-d-Manp-(1 → 2)]-d-Man-ol in a 16:3:1 w/w ratio. Traces of Man-ol and Rha-ol were detected. ESI-MS showed HexHex-ol and Hex3–6Hex-ol components. Three rhamnosyl units were peeled off successively from the penta- and hexasaccharide by ESI-MS-MS. The carbohydrate epitopes of RMP-Sp differ from those of the glycoprotein of Pseudallescheria boydii, a related opportunistic pathogen.