Highly acidic glycans from sea cucumbers

The body wall of the sea cucumber contains high amounts of sulfated glycans, which differ in structure from glycosaminoglycans of animal tissues and also from the fucose‐rich sulfated polysaccharides isolated from marine algae and from the jelly coat of sea urchin eggs. In Ludwigothurea grisea , glycans can be separated into three fractions which differ in molecular mass and chemical composition. The fraction containing a high‐molecular‐mass component has a high proportion of fucose and small amounts of amino sugars, whereas another fraction contains primarily a sulfated fucan. The third fraction, which represents the major portion of the sea cucumber polysaccharides, contains besides fucose, approximately equimolar proportions of glucuronic acid and amino sugars, and has a sulfate content higher than that in the other two fractions. Both D and L‐isomers of fucose are found in these polysaccharides, and the sulfate is linked to the O‐3 position of the fucose residues. The attachment position of the sulfate groups to the glucuronic acid units and amino sugars is still undetermined. It is possible that these compounds are involved in maintaining the integrity of the sea cucumber's body wall, in analogy with the role of other macromolecules in the vertebrate connective tissue.