Inactivation of factor Va by plasmin.

Area of Science:

• Biochemistry
• Hematology
• Molecular Biology

Background:

• Factor Va is a critical cofactor in the prothrombinase complex, essential for blood coagulation.
• Plasmin is a serine protease involved in fibrinolysis, the breakdown of blood clots.
• Understanding Factor Va inactivation is vital for regulating hemostasis and thrombosis.

Purpose of the Study:

• To investigate the inactivation of Factor Va by human plasmin.
• To determine the influence of phospholipid vesicles and calcium ions on this inactivation process.
• To characterize the cleavage patterns and products of Factor Va and its subunits upon plasmin degradation.

Main Methods:

• Polyacrylamide gel electrophoresis (PAGE) for analyzing cleavage patterns.
• Clotting assays to monitor Factor Va inactivation.
• Prothrombin activation measurements using a specific substrate.
• Examination of protective effects of prothrombin and Factor Xa.

Main Results:

• Human plasmin rapidly inactivates Factor Va.
• The rate of Factor Va inactivation by plasmin is significantly enhanced by phospholipid vesicles.
• Plasmin degradation of Factor Va heavy chain (D component) yields different products than activated protein C or Factor Xa.
• Plasmin degradation of Factor Va light chain (E component) produces fragments similar to those generated by activated protein C and Factor Xa.

Conclusions:

• Factor Va inactivation by plasmin is a rapid process, particularly when membrane-bound.
• The phospholipid environment plays a crucial role in accelerating Factor Va inactivation by plasmin.
• Plasmin exhibits distinct substrate specificity towards Factor Va subunits compared to other proteases involved in coagulation regulation.