Characterisation of fucomannopeptide and mannoprotein from Absidia cylindrospora

Abstract

Serologically active mannoprotein (MP, minor fraction) and weak or inactive fucomannopeptide (FMP, major fraction) from the mycelia of Absidia cylindrospora were characterised by methylation analysis and 1H-n.m.r. spectroscopy. MP contained a significant proportion of (1→2)-linked α- d-mannopyranosyl residues with mannopyranosyl non-reducing terminals, whereas FMP consisted of (1→6)-linked α- d-mannopyranosyl residues. MP did not contain a significant amount of mannose branch-units; when treated with 0.1 m NaOH, it was largely fragmented into mannobiose, mannotriose, mannotetraose, and higher oligosaccharides, as shown by gel-permeation chromatography. FMP released 10% of oligosaccharides on treatment by the same procedure. FMP gave a p.m.r. signal for O-acetyl (δ 2.2), its 13C- and 1H-n.m.r. data accorded with the results of the methylation analysis, and the fucopyranosyl residues were shown be α. Acetolysis of FMP gave large proportions of mannose and fucose, and small proportions of Fuc(Man) 3, Fuc(Man) 2, and Fuc-Man. Mild, acid hydrolysis of FMP released fucose and (1→6)-linked, linear α- d-mannosaccharides. Thus, FMP is composed of a (1→6)-linked α- d-mannan to which are attached single fucopyranosyl residues at O-3 of some mannosyl residues, and MP is composed of (1→2)-linked α- d-mannosaccharides which may be linked to the peptide via O-glycosylic linkages. Antibody-precipitating activity of MP with anti- A. cylindrospora serum was twice that of (1→6)-linked α- d-mannan and confirmed that the structure of the mannan moiety of FMP differs from that of serologically active MP.