Carbohydrate Research 337 (2002) 2231 – 2238 www.elsevier.com/locate/carres A 2-sulfated, 3-linked -L-galactan is an anticoagulant polysaccharide Mariana S. Pereira, a Ana-Cristina E.S. Vilela-Silva, a Ana-Paula Valente, b Paulo A.S. Moura ˜o a, * a Laborato ´rio de Tecido Conjuntio, Hospital Uniersita ´rio Clementino Fraga Filho and Departamento de Bioquı ´mica Me ´dica, Centro de Cie ˆncias da Sau ´de, Uniersidade Federal do Rio de Janeiro, Caixa Postal 68041, Rio de Janeiro RJ 21941 -590, Brazil b Centro Nacional de Ressona ˆncia Nuclear Magne ´tica de Macromole ´culas, Departamento de Bioquı ´mica Me ´dica, Uniersidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil Received 1 April 2002; accepted 11 June 2002 Dedicated to Professor Derek Horton on the occasion of his 70th birthday Abstract Marine alga is an abundant source of sulfated polysaccharides with potent anticoagulant activity. However, several attempts to identify the specific structural features in these compounds, which confer the biological activity, failed due to their complex, heterogeneous structure. We isolated and characterized several sulfated -L-galactans and sulfated -L-fucans from marine invertebrates. In contrast to the algal fucans and galactans, these invertebrate polysaccharides have a simple structure, composed of well-defined units of oligosaccharides. We employed two of these compounds to elucidate their structure – anticoagulant action relationship. Our results indicate that a 2-sulfated, 3-linked -L-galactan, but not an -L-fucan, is a potent thrombin inhibitor mediated by antithrombin or heparin cofactor II. The difference between the activities of these two polysaccharides is not very pronounced when factor Xa replaces thrombin. Thus, the anticoagulant activity of sulfated galactan and sulfated fucan is not merely a consequence of their charge density. The interaction of these polysaccharides with coagulation cofactors and their target proteases are specific. Identification of specific structural requirements in sulfated galactans and sulfated fucans necessary for interaction with coagulation cofactors is an essential step for a more rational approach to develop new anticoagulant and antithrombotic drugs. © 2002 Elsevier Science Ltd. All rights reserved. Keywords: Marine invertebrates; Anticoagulant activity; Sulfated polysaccharides; Sulfated galactans; Sulfated fucans 1. Introduction The anticoagulant activity of mammalian gly- cosaminoglycans is mediated by specific plasma cofac- tors, named antithrombin and heparin cofactor II. 1 In the case of heparin, a pentasaccharide sequence, with specific pattern of sugar composition and of sulfation pattern, is required for its interaction with an- tithrombin. 2,3 Dermatan sulfate is another gly- cosaminoglycan with anticoagulant activity, but in this case mediated exclusively by heparin cofactor II. A specific sequence of [4--L-IdUA-2(SO 4 )-1 3--D-Gal- NAc-4(SO 4 )-1] n , where n 3 is required for the binding of dermatan sulfate to the plasma cofactor. 4 One abundant source of new anticoagulant polysac- charides is marine alga. They contain a variety of sulfated fucans 5–9 and sulfated galactans 10–12 with anti- coagulant activity. These compounds are among the most abundant and widely studied of all the polysac- charides from non-mammalian origin. Several attempts to identify in these algal polysaccharides, specific struc- tural features necessary for their anticoagulant activity have been limited by the fact that algal fucans and galactans have complex, heterogeneous structures. 9,12 Their regular repeating sequences are not easily de- duced; even high-field NMR is at the limit of its * Corresponding author. Tel.: +55-21-22703443; fax: + 55-21-25622921/22708647 E -mail address: pmourao@hucff.ufrj.br (P.A.S. Moura ˜o). 0008-6215/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved. PII:S0008-6215(02)00215-X