Enhancement of t-PA-mediated plasminogen activation by partially defucosylated glycosaminoglycans from the sea cucumber Stichopus japonicus.

Sea cucumber glycosaminoglycan (SC-GAG) was isolated from the body wall of the sea cucumber Stichopus japonicus. The SC-GAG consists of a chondroitin sulfate E-type core polymer with sulfated fucose branches attaching glycosidically to almost every disaccharide unit of the core polymer at the C-3 position of the GlcA or at C-4 and/or C-6 position(s) of GalNAc. SC-GAG was subjected to mild acid-hydrolysis, which cleaved selectively the glycosidic linkages between the core polymer and the fucose branches, resulting in two types of partially defucosylated SC-GAG derivatives. One type (type A), obtained by 3 h-hydrolysis, contained 33% of the fucose branches and the other type (type B), obtained by 6-h hydrolysis, contained 10% of the fucose branches. The molecular masses of types A and B were determined to be 8 and 4 kDa, respectively, by gel permeation HPLC. A chondroitinase ABC (Chase ABC)-digestion demonstrated that types A and B contained 46 and 66% of digestable disaccharide units, respectively, and both types contained 29% of E-type unsaturated disaccharide units bearing no fucose branches. Intact SC-GAG and types A and B were compared for t-PA-mediated plasminogen activation by an in vitro assay system. Although intact SC-GAG and type B exhibited rather weak activity at 6.25 microg/ml, type A exhibited 5 to 10-fold higher activity than intact SC-GAG and type B at the same concentration. The activity of type A was almost one-third that of purified chondroitin sulfate E (127 kDa containing 64.5% E-type disaccharide units) from squid cartilage at 6.25 microg/ml concentration. These results suggest that t-PA-mediated plasminogen activation requires the presence of E-type disaccharide units bearing no fucose branches and a molecular mass larger than 7.5 kDa in terms of the chondroitin sulfate E structure with or without fucose branching.