Degradation of β1→6 Galactofuranoside Linkages in the Polysaccharide of Fusarium sp. M7-1 by Endo-β-galactofuranosidase from Bacillus sp

Abstract

A polysaccharide, in which the main part of the side chains were depleted, was prepared from the acidic polysaccharides of Fusarium sp. M7–1 by digestion with lyase of Cellulomonas sp. and mild acid treatment. This polysaccharide was degraded into several fragments, neutral oligosaccharides, neutral polysaccharide, and acidic polysaccharide, by an enzyme, endo-β -galactofuranosidase, produced by Bacillus sp. The main components of the oligosaccharides were isolated and identified as Galf β→6Gal, Glαxl→2Galfβ1→6Gal fβ1→ Glcxl →2Gal fβ1 →6Gal fβ1 →6Gal, Glcxl →2Galfβ 1 →6(Glcαl→2)Gal fβ1 →6Gal and Glcαl →2Ga fβ1 →6(Glcαl → 2)Gal fβ1 →6Galfβ1 →6Gal. The molecular mass of the neutral polysaccharide fragment was estimated to be about 6000 Da by gel filtration chromatography. The polysaccharide fragment consisted of an α1→6 linked mannan main chain to which various sugars, namely Glc, Man, and Rha were attached through α1→3 (or 2) linkages. The molecular mass of the acidic polysaccharide fragment was estimated to be about 6000 Da from the amounts of the reducing terminal galactose. The chemical structures of the oligosaccharides derived from the acidic polysaccharide fragment by mild acid hydrolysis were identified as reported structural units [Iwahara et al., J. Biochem., 112, 355–359 (1992)]. The structure of the mild-acid-resistant part of the acidic polysaccharide fragment was assumed to be a polyuronide to which various sugars such as Glc, Man, and GlcNAc are attached as the side chains. The linkage modes of each sugar are not clear. © 1996, Taylor & Francis Group, LLC. All rights reserved.