NMR study of the galactomannans of Trichophyton mentagrophytes and Trichophyton rubrum

• Published in: Biochemical journal Vol. 323; no. 1; pp. 297 - 305
• Main Authors: Ikuta, K, Shibata, N, Blake, J.S, Dahl, M.V, Nelson, R.D, Hisamichi, K, Kobayashi, H, Suzuki, S, Okawa, Y
• Format: Journal Article
• Language: English
• Published: England 01.04.1997
• Subjects: animal diseases; animal health; Carbohydrate Conformation; Carbohydrate Sequence; human health and safety; Magnetic Resonance Spectroscopy; Mannans - chemistry; medicine; Molecular Sequence Data; mycoses; plant biochemistry; plant physiology; Trichophyton - chemistry
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/bj3230297

Around 90 degrees 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 alpha1,6-linked mannose units, with alpha1,2-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 alpha1,2-linked mannotetraose units connected by an alpha1,6 linkage. The H-1 signals of the two intermediary alpha1,2-linked mannoses of the tetraose unit showed a significant upfield shift (delta delta = 0.05 0.08 p.p.m.). due to the steric effect of an alpha1,6-linked linked mannose unit. The attachment point of the galactose-furanose units was determined at C-3 of the core mannan by the assignment of the downfield-shifted 13C signals of the galactose-mannan 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.