Activated thrombin (factor IIa) prothrombin -> activated thrombin (factor IIa) + thrombin activation peptide (Xa catalyst) Authored: D'Eustachio, P, 2004-08-24 14:00:00 EC Number: 3.4.21 Membrane-bound factor Xa catalyzes the activation of small amounts of thrombin. The amino terminal portion of prothrombin is released as an activation peptide, which can be cleaved further by activated thrombin. Neither the full-length activation peptide nor its cleavage products have known functions. Pubmed14982929 Reactome Database ID Release 43140700 Reactome, http://www.reactome.org ReactomeREACT_1097