Oligosaccharides from depolymerized fucosylated glycosaminoglycan: Structures and minimum size for intrinsic factor Xase complex inhibition

Fucosylated glycosaminoglycan (FG), a structurally complex glycosaminoglycan found up to now exclusively in sea cucumbers, has distinct anticoagulant properties, notably a strong inhibitory activity of intrinsic factor Xase complex (FXase). Knowledge of the FG structures could facilitate the development of a clinically effective intrinsic FXase inhibitor for anticoagulant drugs. Here, a new fucosylated glycosaminoglycan was obtained from the widely traded sea cucumber Bohadschia argus. The precise structure was deduced as {→4)-[l-Fuc3S4S-α-(1→3)-]-d-GlcA-β-(1→3)-d-GalNAc4S6S-β-(1} through analysis of its chemical properties and homogeneous oligosaccharides purified from its β-eliminative depolymerized products. The B. argus FG with mostly 3,4-di-O-sulfated fucoses expands our knowledge on FG structural types. This β-elimination process, producing oligosaccharides with well-defined structures, is a powerful tool for analyzing the structure of complex FGs. Among these oligosaccharides, an octasaccharide displayed potent FXase inhibitory activity. Compared with oligosaccharides with various degrees of polymerization (3n and 3n − 1), our analyses reveal that the purified octasaccharide is the minimum structural unit responsible for the potent selective FXase inhibition, because the d-talitol in the nonsaccharide is unnecessary. The octasaccharide with 2,4-di-O-sulfated fucoses is more potent than that of one with 3,4-di-O-sulfated fucoses. Thus, sulfation patterns can play an important role in the inhibition of intrinsic factor Xase complex.