1. An enzyme (proteinase), formed in shed blood, which converts fibrinogen into fibrin by hydrolyzing peptides (and amides and esters) of L-arginine; formed from prothrombin by the action of prothrombinase.
  2. A sterile protein substance prepared from prothrombin of bovine origin through interaction with thromboplastin in the presence of calcium; causes clotting; used as a topical hemostatic for capillary bleeding in general and plastic surgical procedures.
Synonyms
Factor IIa