Characterization, chemical modifications and in vitro anticoagulant properties of an exopolysaccharide produced by Alteromonas infernus

A new low-molecular-weight 'heparin-like' component was obtained from an ex opolysaccharide produced by a mesophilic strain found in deep-sea hydrother mal vents. Data concerning the structure of the native high-molecular-weigh t exopolysaccharide (10(6) g/mol, 10% sulfate content) are reported for the first time. Two depolymerization processes were used to obtain low-molecul ar-weight (24-35 x 10(3) g/mol) oversulfated fractions (sulfate content 20 or 40%), Nuclear magnetic resonance studies indicated that after sulfation (40%), the low-molecular-weight fraction obtained by free radical depolymer ization was less sulfated in the 6-O-position than the fraction depolymeriz ed by acid hydrolysis. The free radical depolymerized product also had sulf ated residues in the 4-O-position and disulfated ones in the 2,3-O-position s. Moreover, the compounds generated by the free radical process were more homogeneous with respect to molecular mass. Also for the first time, the an ticoagulant activity of the low-molecular-weight exopolysaccharide fraction s is reported. When the fractions obtained after sulfation and depolymeriza tion were compared with heparins, anticoagulant activity was detected in ov ersulfated fractions, but not in native exopolysaccharide. The free radical depolymerized fraction inhibited thrombin generation in both contact-activ ated and thromboplastin-activated plasma, showing a prolonged lag phase onl y in the contact-activated assay. Affinity co-electrophoresis studies sugge sted that a single population of polysaccharide chains binds to antithrombi n and that only a subpopulation strongly interacts with heparin cofactor II . (C) 2001 Elsevier Science B.V. All rights reserved.