Some properties of tissue-type plasminogen activator reconstituted onto phospholipid and/or glycolipid vesicles

Porcine heart tissue-type plasminogen activator (t-PA) was reconstituted onto large multilamellar liposomes with various lipid compositions and the kinetics of plasminogen activation by free or the reconstituted t-PA were studied. Negatively charged lipids, sulfatide and phosphatidylserine (PS), lowered the Km values of t-PA for plasminogen activation (sulfatide, 20-fold; PS, 6-fold), whereas neutral lipid phosphatidylcholine raised the Km. On the other hand, these lipid environments did not affect the amidase parameters and fibrin-binding potency of t-PA. The present results suggest that t-PA could function as a cell-associated form and its plasminogen activation may be regulated by the net charge of the head group of membrane lipids.