Abstract
An anticoagulant protein was purified from the EDTA extract of human placental tissue. The purified protein had a molecular weight of 73, 000 on sodium dodecyl sulfate poly-acrylamide gel electrophoresis under both reducing and non-reducing conditions. Because this protein had the ability to bind phospholipids such as phosphatidylserine, phos-phatidylinositol, and cardiolipin in the presence of Ca2+, this protein was designatedas calphobindin II (CPB-II). CPB-II prolonged the clotting time of normal plasma when coagulation was induced by tissue factor, cephalin and ellagic acid or recalcification, but did not affect thrombin-initiated fibrin formation. CPB-II also inhibited the activation of prothrombin by the complete prothrombinase complex or factor Xa-phospholipid-Ca2+ but not that by phospholipid-free factor Xa. In addition, CPB-II had an inhibitory activity against nhosnholinase A2.
