Which correspond to the backbone 1,6 linked OSI-420 EGFR inhibitor mannose residue substituted by an 1,2 linked mannose residue, and the absence of cross peak 5 were apparent. These results indicated that the long oligosaccharides consist of two side chain oligosaccharides and are connected by a backbone 1,6 linkage at each innermost mannose residue of the oligosaccharides as shown by the structure at the right of each panel. To confirm these structures, the oligosaccharides were digested with 2,3 mannosidase. As the enzyme reaction product, an 1,6 linked mannobiose was obtained from Man6 from the NBRC 0622 and Man5 from the S. cerevisiae mannans. On the other hand, Man5 from the NBRC 103857 mannan produced an 1,6 linkage containing mannotetraose as shown in Fig. 6. These results indicated that the long oligosaccharides consist of two side chain oligosaccharides, and support their 1H NMR assignment result. On the basis of these results, we proposethe possible chemical structures for the cell wall mannans of C. glabrata. The structure of the C. glabrata NBRC 0005 and 0622 mannans is similar to the S. cerevisiae mannan except for the presence of a small amount of the 1,2 linked mannose residue in the tetraose side chain and 1,2 linked mannobiose at the phosphodiester linked site. However, the C. glabrata NBRC 103857 mannan was significantly different from the other two mannans. The two former C. glabrata mannans possessed the 1,3 linkage containing tetraose side chain. On the other hand, the latter mannan did not contain the 1,3 linked mannose residue and the longest side chain was the 1,2 linkage containing triose. Furthermore, the amount of the 1,2 linked mannose residue was significantly greater in the latter mannan compared to the two former mannans. Antifungal drug resistance of C. glabrata strains C. glabrata isolates are known to be associated with higher minimum inhibitory concentrations of all the azoles and are innately less susceptible to all antifungal agents.
The significant difference in the structure of the mannan of the NBRC 103857 strain to that of the other strains led us to compare the susceptibility to the antifungal drugs, itraconazole and micafungin. Interestingly, the NBRC 103857 strain exhibited a significant susceptibility to these antifungal Syk inhibition drugs. Furthermore, relatively strong and moderate susceptibilities to hygromycin B, an inhibitor of protein biosynthesis, were also seen in the NBRC 103857 and NBRC 0005 strains, respectively. However, against the osmotic stress by NaCl, only the NBRC 0622 strain showed a weak susceptibility. Although we also tested the susceptibility to calcofluor white, a chitin and glucan binding reagent, there was no difference in the three strains. Discussion The C. glabrata and S. cerevisiae genomes show a high degree of synteny, and there is anaverage 65% amino acid identity between the orthologous proteins in the two species. In the medically important Candida species, only C. glabrata lacks the ability to produce the pseudohypha formation. C. glabrata and S. cerevisiae are phylogenetically closely related and are quite distinct from the other pathogenic Candida species. Accordingly, the length and the structure of the side chains of both mannans were similar except for the NBRC.