thrombokinase

from The Century Dictionary.

• noun A kinase found in the tissues and the formed elements of the blood, which in the presence of a calcium salt activates the proenzym of the fibrin ferment, thrombogen.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun biochemistry A proteolytic enzyme, that converts prothrombin into thrombin during the clotting of blood

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an enzyme liberated from blood platelets that converts prothrombin into thrombin as blood starts to clot