What serine protease proteolytically degrades both fibrin in clots and native fibrinogen in the circulation into a series of well-characterized end-products collectively known as fibrin/fibrinogen degradation products?

Plasmin

Explanation:

Plasmin is a serine protease found in the blood that is responsible for the degradation of blood plasma proteins such as fibrin and fibrinogen. This process of degradation is referred to as fibrinolysis.

Plasmin degrades fibrin by cleaving specific peptide bonds at several sites located on the fibrin molecules, which results to the dissolution of blood clot and hence the release of degradation end - products called fibrin/fibrinogen degradation products.

The major function of the plasmin enzyme is the lysing of fibrin blood clot and also restoration of the normal flow of blood.