A novel acidic glycogen extracted from the marine sponge Aplysina fulva (porifera-demospongiae)

Abstract

Polysaccharides were extracted from the marine sponge Aplysina fulva by papain digestion and precipitation with cetylpyridinium chloride. Eluted from an anion-exchange column with a pH gradient, the sponge polysaccharides yielded two distinct fractions, denoted S1 and S2. The S1 fraction, which was eluted at low pH, constitutes about 0.2% of the sponge dry weight, migrates as a single band on agarose gel electrophoresis, and has a simpler chemical composition than the S2 fraction, which is eluted at more alkaline pH. The S1 fraction was further purified by ion-exchange and gel-permeation chromatography. Methylation, 1H and 13C NMR, amyloglucosidase digestion, specific optical rotation, infrared spectroscopy and the reaction with iodine established that the sponge glucan is a form of glycogen. However, the sponge polysaccharide, unlike oyster and rabbit liver glycogen, has an acidic property that causes it to bind to a DEAE-cellulose column at low ionic strength (pH 5.0). Chemical composition and infrared spectroscopy revealed considerable amounts of sulfate esters (≈ 0.05 moles/mole of glucose) in the sponge molecule. Comparative methylation analysis of the intact and desulfated S1 fraction suggests that about 50% of the non-reducing ends of the sponge polysaccharide are sulfated d-glucose residues, perhaps at position O-4.