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

Abstract

A particulate polysaccharide was isolated by differential centrifugation and alkali extraction from homogenates of the cestode Moniezia expansa. The polysaccharide had the structure of a glycogen. Its chemical properties, infra-red spectrum and optical rotation showed that it consisted of alpha-1,4- and alpha-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 alpha- and beta-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 about s20, w = 600, but the alkali extracted material had an s20, 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 glycogen, alpha, beta- and possible gamma-particles being identified by electron microscopy. The alpha-particles were relatively stable under acidic conditions remaining intact down to pH 2-5. At pH 1-7 the alpha-particles dissociated into their constituent beta-particles with a consequent decrease in the opalescence of the solution. The nitrogen content of 0-9% was high for a glycogen.