Institution: | a Departamento de Bioquímica, Universidade Federal do Paraná, Cx.P. 19046, 81531-990, Curitiba, Paraná, Brazil b Departamento de Genética, Universidade Federal do Paraná, Cx.P. 19071, 81531-990, Curitiba, Paraná, Brazil c Istituto di Chimica e Biochimica G. Ronzoni, Milan, Italy |
Abstract: | Guignardia citricarpa is a phytopathogenic fungus and the causal agent of citrus black spot. Incubation in a semi-defined media resulted in formation of exopolysaccharides EPS(s)]. A medium containing glucose gave rise to a (1→6)-linked β-glucan (200 kD), pustulan, which was characterized by NMR and methylation analysis. A sucrose-containing medium provided a homogalactan (376 kD) and methylation analysis showed nonreducing end- (20%), 6-O- (53%) and 5,6-di-O-substituted Galf units (27%). An HMQC spectrum of the homogalactan showed C-1/H-1 signals at δ 108.2/4.820, 108.3/4.820 and 107.1/5.079, corresponding to three types of β-
-Galf units. A DEPT analysis showed inverted signals (CH2) at δ 67.8 and 67.2, corresponding to 6-O-substituted β-
-Galf units, whereas a C-5 signal at δ 77.0 suggests 5-O-substitution, confirming a novel structure for a β-galactofuranan. |