Fonsecaea pedrosoi is the main etiologic agent of chromoblastomycosis, usually occurring in tropical and subtropical areas. The cell wall components of pathogenic microorganisms behave as an antigen and/or ligand of the innate immune response. The cells of F. pedrosoi reacted with the α-galactopyranose-binding lectin (Griffonia simplicifolia lectin 1B4 isolectin, GSL 1B4), as well as the α-mannose-binding lectin, concanavalin A. The cell wall glycoprotein was isolated from conidial cells of F. pedrosoi, and its structure was analyzed by (1)H-nuclear magnetic resonance (NMR) and (13)C-NMR experiments. The N-linked polysaccharide moiety consists of a backbone β-1,6-linked galactofuranose and α-1,6-linked mannose polymers, both of which are substituted with α-1,2-linked glucose side-chains. Furthermore, the glycoprotein contained a large amount of O-linked oligosaccharides, especially a hexaose that constituted approximately 20% of the glycoprotein. Unexpectedly, the hexaose had a highly branched structure which consisted of galactofuranose, galactopyranose, glucose and mannose residues as follows: aDGlcp(1-2)bDGalf(1-6)[aDGalp(1-3),aDGalp(1-2)]aDManp(1-2)?DManp. An anti-F. pedrosoi antibody specifically reacted with the cells of F. pedrosoi, whereas other fungal cells that contain galactofuranose residues did not react. The reactivity of the antibody was strongly inhibited by the branched hexaose, suggesting that the characteristic structure of the O-linked hexaose involves the antigenic specificity of the cells.

oligosaccharide, polysaccharide, NMR spectroscopy, Galactomannan, β-elimination

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
2,2	aDGalp	101.77	69.54	70.26	70.26	?	62.17
2,3	aDGalp	101.77	69.54	70.26	70.26	?	62.17
2,6,2	aDGlcp	99.08	72.01	73.74	70.26	73.17	61.44
2,6	bDGalf	107.02	87.65	76.15	83.02	71.38	63.77
2	aDManp	101.53	79.50	78.35	67.49	?	67.49
	aDManp	93.46	80.24	70.84	68.00	?	61.91


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
2,2	aDGalp	5.287	3.850	3.998	4.091	?	?
2,3	aDGalp	5.225	3.801	3.883	4.029	?	?
2,6,2	aDGlcp	5.059	3.584	3.715	3.451	3.781	3.878
2,6	bDGalf	5.160	4.133	4.253	4.021	3.853	3.672-3.724
2	aDManp	5.332	4.219	4.034	3.755	?	?
	aDManp	5.366	3.915	3.929	3.780	?	?


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
2,2	aDGalp	101.77/5.287	69.54/3.850	70.26/3.998	70.26/4.091	?/?	62.17/?
2,3	aDGalp	101.77/5.225	69.54/3.801	70.26/3.883	70.26/4.029	?/?	62.17/?
2,6,2	aDGlcp	99.08/5.059	72.01/3.584	73.74/3.715	70.26/3.451	73.17/3.781	61.44/3.878
2,6	bDGalf	107.02/5.160	87.65/4.133	76.15/4.253	83.02/4.021	71.38/3.853	63.77/3.672-3.724
2	aDManp	101.53/5.332	79.50/4.219	78.35/4.034	67.49/3.755	?/?	67.49/?
	aDManp	93.46/5.366	80.24/3.915	70.84/3.929	68.00/3.780	?/?	61.91/?

The spectrum also has 4 signals at unknown positions (not plotted).

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

OC[C@@H](O)[C@@H]1O[C@@H](OC[C@H]2O[C@H](O[C@@H]3[C@@H](O)O[C@H](CO)[C@@H](O)[C@@H]3O)[C@@H](O[C@H]3O[C@H](CO)[C@H](O)[C@H](O)[C@H]3O)[C@@H](O[C@H]3O[C@H](CO)[C@H](O)[C@H](O)[C@H]3O)[C@@H]2O)[C@H](O[C@H]2O[C@H](CO)[C@@H](O)[C@H](O)[C@H]2O)[C@H]1O

990.861 g/mol (C₃₆H₆₂O₃₁)