Cell wall mannan of human pathogen Candida dubliniensis

Abstract

Cell wall mannan isolated and purified from the human pathogen yeast Candida dubliniensis CCY 29-177-1 has been characterized. The polysaccharide of M w = 35,000 was composed of d-mannose and trace amount of d-glucose residues. Compositional and methylation analyses of the polymer, acetolysis as well as 1H and 13C NMR measurements pointed to a highly branched structure of C. dubliniensis mannan. Its backbone was composed of α-1,6-linked mannose residues branched at O-2 by side mannose residues as single stubs, as well as side oligosaccharide chains of d.p. 2–7, mostly in the form of tri-, di- and tetramers. Longer side chains, penta, hexa- and heptamers, were found in lesser amounts. NMR spectra showed that oligosaccharide side chains were formed by α-1,2- and α-1,3-linked mannose residues. In addition, the presence of higher quantity of oligosaccharides with terminal Manβ(1 → 2)Manβ(1 → fragment was deduced on the basis of characteristic signals in the HSQC spectrum of polymer mannan.