Existence of novel branched side chains containing β-1,2 and α-1,6 linkages corresponding to antigenic factor 9 in the mannan of Candida guilliermondii

Isolation of β-linkage-containing side chain oligosaccharides from the mannan of Candida gilliermondii IFO 10279 strain has been conducted by acetolysis under mild conditions. A structural study of these oligosaccharides by one- and two-dimensional NMR and methylation analyses indicated the presence of extended oligosaccharide side chains with two consecutive β-1,2-linked mannose units at the nonreducing terminal of α- linked oligosaccharides. The linkage sequence present in this mannan, Manβ1→2Manα1→3Manα→, has also been found in the mannan of Saccharomyces kluyveri but not in the mannan of Candida species. Furthermore, these oligosaccharides are branched at position 6 of the 3-O- substituted mannose units. The H-1 signals of the mannose units substituted by a 3,6-di-O-substituted unit showed a significant upfield shift (Δδ = 0.04-0.08 ppm) due to a steric effect. The inhibition of an enzyme-linked immunosorbent assay between the mannan of C. guilliermondii and factor 9 serum with oligosaccharides obtained from several mannans indicated that only the oligosaccharides with the above structure were active, suggesting that these correspond to the epitope of antigenic factor 9.