Chemical structure of the cell-wall mannan of Candida albicans serotype A and its difference in yeast and hyphal forms

Abstract

The structure of the cell-wall mannan from the J-1012 (serotype A) strain of the polymorphic yeast Candida albicans was determined by acetolysis under mild conditions followed by HPLC and sequential NMR experiments. The serotype A mannan contained β-1,2-linked mannose residues attached to α-1,3-linked mannose residues and α-1,6-linked branching mannose residues. Using a β-1,2-mannosyltransferase, we synthesized a three-β-1,2-linkage-containing mannoheptaose and used it as a reference oligosaccharide for 1H-NMR assignment. On the basis of the results obtained, we derived an additivity rule for the 1H-NMR chemical shifts of the β-1,2-linked mannose residues. The morphological transformation of Candida cells from the yeast form to the hyphal form induced a significant decrease in the phosphodiesterified acid-labile β-1,2-linked manno-oligosaccharides, whereas the amount of acid-stable β-1,2 linkage-containing side chains did not change. These results suggest that the Candida mannan in candidiasis patients contains β-1,2-linked mannose residues and that they behave as a target of the immune system.