NMR study of the galactomannans of Trichophyton mentagrophytes and Trichophyton rubrum.
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 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 (Deltadelta=0.05-0.08 p.p.m.), due to the steric effect of an alpha1,6-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.
Ikuta
K
K
Second Department of Hygienic Chemistry, Tohoku College of Pharmacy, 4-4-1 Komatsushima, Aoba-ku, Sendai, Miyagi 981, Japan.
Shibata
N
N
Blake
J S
JS
Dahl
M V
MV
Nelson
R D
RD
Hisamichi
K
K
Kobayashi
H
H
Suzuki
S
S
Okawa
Y
Y
D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D005690:Galactose / Q000031:analogs & derivatives; D009682:Magnetic Resonance Spectroscopy; D008351:Mannans / Q000737:chemistry*; D008969:Molecular Sequence Data; D014249:Trichophyton / Q000737:chemistry*
D008351:Mannans; C012990:galactomannan; D005690:Galactose