Structure of cell wall mannan of Candida kefyr IFO 0586

Abstract

We conducted a structural analysis of the antigenic cell wall mannoprotein (mannan) isolated from Candida kefyr (formerly Candida pseudotropicalis) IFO 0586. The result of two-dimensional homonuclear Hartmann-Hahn analysis of this mannan indicates that the molecule is constructed from α-1,2- and α- 1,6-linked mannopyranose residues. Upon alkali treatment (β-elimination reaction), this mannan released two α-1,2-linked mannooligosaccharides, biose and triose. The structure of the alkali-stable mannan (outer chain) moiety was investigated by acetolysis. The structures of the resultant oligosaccharides, biose and triose, from the outer chain moiety were found to be the same as those of the alkali-released ones. Further, the treatment of the parent mannan with an Arthrobacter GJM-1 exo-α-mannosidase gave a linear mannan consisting solely of α-1,6-linked mannopyranose residues. These results indicate that the mannan forms the long backbone of the α-1,6 linkage, with a large number of short α-1,2-linked oligomannosyl side chains forming a comblike structure. Moreover, we investigated the serological properties of this mannan by performing an inhibition assay of a slide agglutination reaction with mannooligosaccharides and polyclonal factor sera (Candida Check; Iatron). The result indicates that the factor 1 serum preferentially recognizes the α-1,2-linked oligomannosyl side chains in this mannan. On the other hand, the fact that the mannan does not contain an antigenic determinant(s) corresponding to factor 8 suggests that the epitope(s) of this factor resides in other molecules on the cell surface of this strain.