A branched (1→3)-β- d-glucan from a water extract of Dictyophora indusiata Fisch

Abstract

A water-soluble, (1→6)-branched, (1→3)-β- d-glucan (T-3-G), [α] D 27 +40.8° ( c 0.123, water), was isolated from a hot-water extract of the fruit bodies of Dictyophora indusiata Fisch. T-3-G was homogeneous as judged by ultracentrifugal analysis, Tiselius-type electrophoresis, and gel filtration. By gel filtration on Sepharose CL-2B, with 0.25 m sodium hydroxide as the eluant, the molecular weight ( M w) of T-3-G was estimated to be ∼5.1 × 10 5. From the results of methylation analysis, periodate oxidation, Smith degradation, and enzymic hydrolysis, it was concluded that T-3-G has a main chain composed of β-(1→3)-linked d-glucopyranosyl residues, and two single, β-(1→6)-linked d-glucopyranosyl groups attached as side chains to, on average, every five sugar residues of the main chain. In addition, the results of enzymic hydrolysis indicated that the branching of T-3-G occurs regularly at O-6 of the β-(1→3)-linked backbone. The results of optical rotatory measurements and complex-formation with Congo Red suggested that T-3-G probably takes a triple-helical conformation.