ANTICOAGULANT ACTIVITY OF A HEPARIN FROM ASCIDIAN

ANTICOAGULANT ACTIVITY OF A HEPARIN FROM ASCIDIAN PHALLUSIA
NIGRA (CHORDATA: TUNICATA)
Christiane F. Sobral, Eliene O. Kozlowski and Mauro S. G. Pavão
from Laboratório de Tecido Conjuntivo, Hospital Universitário Clementino Fraga
Filho and Instituto de Bioquímica Médica, UFRJ
Heparin is a well-known glycosaminoglycan for its ability to prevent blood
coagulation. Although heparin from mammalian origin is clinically used as an
anticoagulant drug, the appearance of bovine prion diseases and the haemorragic
effect of high doses of heparin have limited its use. Therefore to look for new
sources of heparin-like compounds is an important goal of glycobiologists. In this
work, a heparin-like glycan was extracted from ascidian Phallusia nigra and
purified using anion-exchange chromatography on a DEAE-cellulose and MONOQ/FPLC columns. The ascidian heparin has a low molecular weight glycan (~12
KDa), as determined by PAGE in barbital buffer. The anticoagulant activity was
meansured by the aPTT assay, in which it showed a ~60-fold lower anticoagulant
activity (3 units/mg) then bovine heparin (180 units/mg). Ascidian heparin is able to
inhibit factor Xa via antithrombin (IC 50 = 3.14 µg/mL), but thrombin inhibition was
very lower (IC 50 = 0.74 µg/mL), as comparing with mammalian heparin (IC 50 =
0.143 µg/mL and IC 50 = 0.90 ng/mL, respectively). Taken together, these results
point to a selective activity of the ascidian heparin as a factor Xa inhibitor. A
detailed study about the structure of this heparin is being performed to establish a
correlation among the low molecular weight, structural features and anticoagulant
activity.
Key words: ascidian, anticoagulant, glycosaminoglycan, heparin
Financial support: CAPES, CNPq, FAPERJ, NIH-FIC (R03TW05775)