Plasmin-mediated proteolysis of human factor IXa in the presence of calcium/phospholipid: Conversion of procoagulant factor IXa to a fibrinolytic enhancer.

Background: Factor (F) IX/IXa inactivation by plasmin has been studied; however, whether plasmin converts FIXa to a fibrinolytic enhancer is not known.

Objective: Investigate plasmin proteolysis site(s) in FIXa that inactivates and transforms it into a fibrinolytic enhancer.

Methods: NH -terminal sequencing, mass spectrometry analysis, and functional assays.