Abstract
Around 90% of chronic dermatophyte infections are caused by the fungi Trichophyton mentagrophytes and Trichophyton rubrum. One of the causes of the chronic infection resides in the immunosuppressive effects of the cell-wall components of these organisms. Therefore we have attempted to identify the chemical structure of galactomannan, one of the major cell-wall components. The cell-wall polysaccharides secreted by T. mentagrophytes and T. rubrum were isolated from the culture medium and fractionated into three subfractions by DEAE-Sephadex chromatography. Analysis of each subfraction by NMR indicated that there are two kinds of polysaccharides present, i.e. mannan and galactomannan. The mannan has a linear backbone consisting of α1,6-linked mannose units, with α1,2-linked mannose units as side chains. The core mannan moiety of the galactomannan was analysed by a sequential NMR assignment method after removing the galactofuranose units by acid treatment. The result indicates that the mannan moiety has a linear repeating structure of α1,2-linked mannotetraose units connected by an α1,6 linkage. The H-1 signals of the two intermediary α1,2-linked mannoses of the tetraose unit showed a significant upheld shift (Δδ = 0.05-0.08 p.p.m.), due to the steric effect of an α1,6-linked mannose unit. The attachment point of the galactofuranose units was determined at C-3 of the core mannan by the assignment of the downfield-shifted 13C signals of the galactomannan compared with those of the acid-modified product. In these galactomannans there were no polygalactofuranosyl chains which have been found in Penicillium charlesii and Aspergillus fumigatus.
Original language | English (US) |
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Pages (from-to) | 297-305 |
Number of pages | 9 |
Journal | Biochemical Journal |
Volume | 323 |
Issue number | 1 |
DOIs | |
State | Published - Apr 1 1997 |