title: Platelet factor XIII is activated by calpain.
abstract: The action of calpain (EC 3.4.22.17; Ca2+-dependent cysteine proteinase) on platelet factor XIII has been studied. Calpain I activated platelet factor XIII up to 76% of the maximum level observed with thrombin. Activation was accompanied by the limited proteolysis of the a subunit of platelet factor XIII to produce a 76 kDa fragment which was comparable to the proteolytic product by thrombin. Activation of platelet factor XIII by calpain was inhibited by EDTA, leupeptin, and endogenous calpain-specific inhibitor calpastatin. These findings suggest that calpain is responsible for the intracellular activation of platelet factor XIII.
mesh_terms: D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism; D002118:Calcium / Q000097:blood; D002135:Calcium-Binding Proteins / Q000494:pharmacology; D002154:Calpain / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D005176:Factor XIII / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007976:Leupeptins / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology; D011503:Transglutaminases / Q000097:blood
chemical_list: D002135:Calcium-Binding Proteins; D007976:Leupeptins; C033668:calpastatin; D005176:Factor XIII; D011503:Transglutaminases; D013917:Thrombin; D002154:Calpain; C032854:leupeptin; D002118:Calcium