Plasma Lipoproteins Support Prothrombinase and Other Procoagulant Enzymatic Complexes

The prothrombinase complex (factor [F]Xa, FVa, calcium ions, and lipid membrane) converts prothrombin to thrombin (FIIa). To determine whether plasma lipoproteins could provide a physiologically relevant surface, we determined the rates of FIIa production by using purified human coagulation factors, and isolated fasting plasma lipoproteins from healthy donors. In the presence of 5 nmol/L FVa, 5 nmol/L FXa, and 1.4 [micro sign] mol/L prothrombin, physiological levels of very low density lipoprotein (VLDL) (0.45 to 0.9 mmol/L triglyceride, or 100 to 200 [micro sign] mol/L phospholipid) yielded rates of 2 to 8 nmol FIIa [center dot] L [center dot] s in a donor-dependent manner. Low density lipoprotein (LDL) and high density lipoprotein (HDL) also supported prothrombinase but at much lower rates (