Molecular structure and morphology of glycogen isolated from the cestode,Moniezia expansa

Abstract

SummaryA particulate polysaccharide was isolated by differential centrifugation and alkali extraction from homogenates of the cestodeMoniezia expansa. The polysaccharide had the structure of a glycogen. Its chemical properties, infra-red spectrum and optical rotation showed that it consisted of α-1, 4- and α-1, 6-linked glucopyranose units. Examination of the complex with iodine and the precipitate with concanavalin-A showed that the structure was highly branched. Oxidation with periodate and hydrolysis with α- and β-amylase were used to measure mean chain lengths. For the particulate preparation the average chain length was 12·9 glucose units and the exterior and interior chain lengths were 9·0 and 2·9 units respectively. The particulate preparation had a very high sedimentation constant (s20, w= 910) with a smaller component at abouts20, w= 600, but the alkali extracted material had ans20, w= 61 similar to that shown by alkali degradation of the particulate preparation. The morphology of the particulate material was similar to that of rat liver glycoge, α, β- and possible γ-particles being identified by electron microscopy. The α-particles were relatively stable under acidic conditions remaining intact down to pH 2·5. At pH 1·7 the α-particles dissociated into their constituent β-particles with a consequent decrease in the opalescence of the solution. The nitrogen content of 0·9% was high for a glycogen.