A fucosylated glycosaminoglycan (AmFG) was extracted from the sea cucumber Acaudina molpadioides. And a series of oligosaccharides were purified from the size-homogeneous fractions, which were prepared from the β-eliminative depolymerized AmFG. According to "bottom-up" strategy, the precise structure of AmFG was elucidated by analyzing the structures of these purified oligosaccharides, combining with NMR analysis of its free-radical depolymerized product. It contained a CS-E-like backbone, and each GlcUA was branched with a mono- or di-sulfated fucose (Fuc) at O-3. Intriguingly, besides two types of monosaccharide branches, Fuc2S4S (60 %) and Fuc4S (25 %), that were common in FG, AmFG also contained an unusual disaccharide branch GalNAc-α1,2-Fuc3S4S (15 %); this is the first report of such a structure in a glycosaminoglycan. Biological assays indicated that native AmFG and its oligosaccharides had potent anticoagulant and intrinsic tenase (iXase) inhibitory activities in a chain length-dependent manner. For these oligosaccharides, octasaccharide was the minimum structural fragment for potent anti-iXase activity, and the disaccharide branch might enhance this activity.
Keywords: Anticoagulant; Disaccharide branch; Fucosylated glycosaminoglycan; Intrinsic tenase; Oligosaccharide.
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