Structural analysis of mannans from Candida albicans serotypes A and B and from Torulopsis glabrata by methylation gas chromatography mass spectrometry and exo-alpha-mannanase.

Abstract

Mannans of Candida albicans serotypes A and B and of Torulopsis glabrata were subjected to methylation analysis and the resulting monosaccharides were converted to the peracetylaldononitrile derivatives and subsequently analyzed by gas chromatography mass spectrometry. Serotype A differed from B in having more 1 leads to 2 linked mannosyl residues (46.2 vs 37.1 mol%) indicating longer oligomannosyl sidechains; mannosyl branch points linked through C-1, C-3 and C-6 were detected for the first time in C. albicans mannans and were more abundant in serotype B (9.2 vs 5.3 mol%). T. glabrata mannan differed from that of C. albicans in having virtually no (1.6 mol%) unsubstituted sugars in the linear backbone and less 1 leads to 2 linked mannosyl residues (33.1 mol%) interpreted as shorter oligomannosyl sidechains. Model building of a repeating unit for the outer chain region of these mannans was prevented by the large amount of nonreducing terminal mannosyl residues, 23.0 mol% for C. albicans A, that probably arise from the inner core region. These mannans were exposed to exo-alpha-mannanase and the percentage of digestion, measured as reducing sugar released, was 33.5% for C. albicans B; 27.4% for T. glabrata, and C. albicans A was refractory (5.4% digested).