A novel glycosaminoglycan from the brittlestar Trichaster palmiferus: structure and low-bleed anticoagulant-antithrombotic action.

Safe, potent, and low-bleeding anticoagulants remain an unmet medical need. Here we report a homogeneous glycosaminoglycan (GAG), designated TPG, isolated from the brittlestar Trichaster palmiferus. TPG (30.3 kDa, 32% sulfate) is composed of an almost equimolar ratio of L-Iduronic acid (IdoA) and N-acetyl-D-galactosamine (GalNAc) together with minor D-glucosamine (GlcN), D-galacturonic acid (GalA), and D-galactose (Gal). These physicochemical properties are distinct from heparin, dermatan sulfate, and chondroitin sulfate. Using one- and two-dimensional NMR of its desulfated derivative, free-radical depolymerized fragments, and oligosaccharide fractions generated by partial N-deacetylation-deamination cleavage, we established that the polymer backbone is built from four repeating disaccharides: L-IdoA2S3S-α-1,3-D-GalNAc4S/6S-β-1,4-, L-IdoA2S-α-1,3-D-GalNAc4S/6S-β-1,4-, D-GalA-α-1,3-D-GalNAc4S-β-1,4-, and D-GalNAc4S-β-1,4-GlcN0S/6S-α-1,3-. The IdoA2S3S and GalA residues and the D-GalNAc4S-β-1,4-GlcN0S/6S-α-1,3- unit are rare in natural GAGs, rendering TPG resistant to chondroitinase ABC. NMR detected terminal Gal in desulfated TPG and large oligosaccharide fragments, but its connection pattern remains unclear. TPG prolongs clotting times by simultaneously blocking intrinsic factor Xase and potentiating HCII-mediated thrombin inhibition, and it achieves potent antithrombotic efficacy in vivo with virtually no bleeding, an advantage over enoxaparin. These findings establish a brittlestar GAG whose unusual sulfation pattern defines a new class of high-efficacy, low-bleeding anticoagulants.