title: Activation of coagulation factor V by calcium-dependent proteinase.
abstract: Factor V is a key coagulation cofactor, regulating the rate of Factor Xa-catalyzed prothrombin conversion. Activation of Factor V markedly accelerates coagulation. This study describes a new class of Factor V activators, sulfhydryl proteinases. Of the enzymes studied, calcium-dependent proteinase was the most effective activator. Activation of Factor V by this enzyme was associated with cleavage of 125I-labeled Factor V to peptides distinct from those generated by previously described activators. Calcium-dependent proteinase-activated Factor Va peptides with molecular weights of 114,000 and 93,000 bound both to Factor Xa and to cultured endothelial cells. Calcium-dependent proteinase was identified in vascular endothelial cells, a tissue that also synthesizes Factor V. These findings suggest a previously unknown mechanism for cellular regulation of coagulation.
mesh_terms: D000818:Animals; D002154:Calpain / Q000494:pharmacology*; D002645:Chickens; D003546:Cysteine Endopeptidases; D010450:Endopeptidases / Q000494:pharmacology; D004727:Endothelium / Q000378:metabolism; D005165:Factor V / Q000378:metabolism*; D015943:Factor Va; D005170:Factor X / Q000378:metabolism; D015951:Factor Xa; D006801:Humans; D008970:Molecular Weight; D013917:Thrombin / Q000494:pharmacology
chemical_list: D015943:Factor Va; D005165:Factor V; D005170:Factor X; D010450:Endopeptidases; D013917:Thrombin; D015951:Factor Xa; D002154:Calpain; D003546:Cysteine Endopeptidases