Isolation of side chain oligosaccharides from mannans of Candida albicans NIH B-792 (serotype B) and Candida parapsilosis IFO 1396 strains has been conducted by acetolysis under mild conditions. Structural study of these oligosaccharides by 1H and 13C NMR and methylation analyses indicated the presence of novel branched side chains with the following structures in C. albicans mannan. [sequence: see text] It was observed that the H-1 proton chemical shifts of the second and the third mannose units from the reducing terminus in each oligosaccharide are shifted upfield by substitution with an alpha-linked mannose unit at position 6 of the 3-O-substituted mannose unit. An agglutination inhibition assay between factor 4 serum and cells of Candida stellatoidea IFO 1397 lacking the beta-1,2-linked mannose unit, with oligosaccharides obtained from these mannans, indicated that only the branched oligosaccharides were active. This finding suggests that the branched oligosaccharides correspond to the epitope of antigenic factor 4. The presence of the branched structure in other mannans was detected by the characteristic H-1-H-2-correlated cross-peak of the alpha-1,2-linked mannose unit connected with the 3,6-di-O-substituted one by two-dimensional homonuclear Hartmann-Hahn spectroscopy.

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Acetolysis of the cell-wall mannan of Saccharomyces kluyveri under mild conditions, gave fragments with 1-6 mannose residues. The structures of mannopentaose and mannohexaose were determined to be Manal+3Manal-+2Manal+2Man 1 6 Manal and Manfil+2Manal+3Mannl+2Manal+2Man, FManal respectively, by two-dimensional homonuclear Hartmann-Hahn spectroscopy and a sequential NMR assignment method that combines 'H-I3C correlated spectroscopy, relayed coherence transfer spectroscopy, 'H-detected heteronuclear multiple-bond connectivity and methylation analysis. The HI proton chemical shift of a neighboring a-1,2-linked mannose unit of the 3-0-substituted structure was shifted upfield by the addition of a mannose unit to the adjacent 3-0-substituted unit by an a-1,6 linkage. The characteristic H1 -H2-correlated cross-peak of the a-1,3-linked mannose unit substituted by a B1,2 linkage, pl+2Mana1+3, in the mannan of S. kluyveri, as also found by twodimensional homonuclear Hartmann-Hahn spectroscopy in the rnannan of Cundidu guilliermondii, a pathogenic yeast in man.In a previous study, it was found that mannans of the pathogenic yeast, Candida albicans, strains NIH A-207 (serotype A), NIH B-792 (serotype B) and J-1012 (serotype A) all contained /3-1,2-linked mannose units [l -81. Furthermore, we defined that a P-1,2-linked mannose unit is linked to an a-1,2-linked unit, Manfil+2Manal+2Manal+ andManpl-+2Manpl+2Manal-+2Manal-+, and that these specific structures are present in serotype-A epitopes corresponding to antigenic factor 6 in C. albicans species [9]. The phosphodiesterified p-1,2-linked oligomannosyl residues, Man,!ll+(2Manpl+),2Man (n = 0-5), are common feaCorrespondence to S. Suzuh, The Second Department of Hygienic Chemistry, Tohoku College of Pharmacy, 4-4-1 Komatsushima, Sendai Aoba-ku, Miyagi, Japan 981 Abbreviations. 2D, two-dimensional; HOHAHA, homonuclear Hartmann-Hahn spectroscopy ; COSY, correlated spectroscopy ; relayed COSY, relayed coherence transfer spectroscopy; HMBC, 'Hdetected heteronuclear multiple-bond connectivity; Fr. S, alkalimodified mannan: SM,, mannooligosaccharide obtained after mild acetolysis, where x indicates number of mannose residues; SM,-e, a-rnannosidase-resistant hexaose; SM,-eH, NaBH,-reduction product of SM,-e. tures present in the mannans of strains of both serotypes A and €3, and correspond to antigenic factor 5 [lo].However, Zhang and Ballou [111 reported the presence of a fi-1,2-linked mannose unit, in the oligomannosyl moiety which can be /? eliminated, for the 0-glycosylated form. This unit is linked to serine and/or threonine in the peptide moiety of a mannoprotein of Saccharomyces kluyveri. In this study [l I], the structure of the oligomannosyl residue containing the p-1,2 linkage was determined to be Manpl+2Mana 1 +3Manal+2Manal+2Manal +Ser/Thr I6Manal .