Heparin from marine mollusks: Occurrence, structure, and biological role

Several invertebrate species contain variable amounts of one or more types of sulfated glycosaminoglycans (GAGs). At present it is well known the existence of a species-specific sulfated GAGs composition based on the relative amount and type of chondroitin sulfates, heparan sulfate and heparin. Heparin is a sulfated polysaccharide belonging to the family of GAGs with numerous important biological activities, such as anticoagulant and antithrombotic properties that derive from its interaction with diverse proteins. Unusual heparin samples for molecular mass, fine structural organization and anticoagulant activity, are isolated and characterized from molluscs. Variable presence of the trisulfated disaccharide [DUA2S(1->4)-a-D-GlcN2S6S] and significant modifications of the disaccharides bearing non-sulfated iduronic and glucuronic acids, [->4)-a-L-IdoA(1->4)-a-DGlcNAc6S( 1-> and ->4)-a-L-IdoA(1->4)-a-D-GlcN2S6S(1->] and [->4)-b-D-GlcA(1->4)-a-DGlcN2S6S( 1->], and oligosaccharide sequences bearing part of the ATIII-binding region, [DUA2S(1->4)-a-D-GlcN2S6S(1->4)-b-D-GlcA(1->4)-a-D-GlcN2S3S6S] and [DUA2S (1->4) -a-DGlcN2S6S (1->4)-a-L-IdoA (1->4)-a-D-GlcNAc6S (1->4)-b-D-GlcA (1->4)-a-D-GlcN2S3S6S], are detected and measured in heparin samples derived from different clam species. This review more specifically deals with structural and biologically important aspects of heparin in invertebrates with special emphasis on the heparin from molluscs. Furthermore, the fine characterization of heparin from Tapes phylippinarum and Callista chione is reported.