Fractionation and partial characterization of the sulphated polysaccharide of Porphyridium

The carbohydrate composition of the extracellular sulphated polysaccharide obtained from cultures of the unicellular red alga Porphyridium was determined. The polysaccharide was separated by anion-exchange chromatography into eight fractions. The major carbohydrate-containing fractions, accounting for ca 89% of the total carbohydrates, were the 0.5, 1.0 and 2.0 M NaCl fractions and the hot urea fraction. The NaCl-eluted fractions showed very similar neutral sugar compositions, with some differences in the contents of sulphate and uronic acid, which increased from the 0.5 M to the 2 M NaCl fraction. The hot urea fraction was apparently a xylan (about 86% xylose) and accounted for about 72% of the protein found in the whole polysaccharide. These findings indicate the presence of at least two different polysaccharides, one of which seems to be a proteoglycan. Amino acid analysis of the latter fraction was performed.