Prothrombinase acceleration by oxidatively damaged phospholipids

The optimally efficient production of thrombin by the prothrombinase comple x relies on suitable positioning of its component factors and substrate on phosphatidylserine-containing lipid membranes. The presence of oxidatively damaged phospholipids in a membrane disrupts the normal architecture of a l ipid bilayer and might therefore be expected to interfere with prothrombina se activity. To investigate this possibility we prepared phosphatidylserine -containing lipid vesicles containing oxidized arachidonoyl lipids, and we examined their ability to accelerate thrombin production by prothrombinase. Oxidized arachidonoyl chains caused dose-dependent increases in prothrombi nase activity up to 6-fold greater than control values. These increases wer e completely attenuated by the presence of alpha-tocopherol, gamma-tocopher ol, or ascorbate. Over the course of a 300-min oxidation, the ability of ar achidonoyl lipids to accelerate prothrombinase peaked at 60 min and then de clined to base-line levels. These results suggest that instead of being imp eded by oxidative membrane damage, prothrombinase activity is enhanced by o ne or more products of nonenzymatic lipid oxidation.