title: The binding of calcium to fibrinogen: influence on the clotting process.
abstract: The influence of Ca2+ on the basic reaction between thrombin and fibrinogen was investigated. The results demonstrate that: (a) A Ca2+-dependent dimeric intermediate is formed during the early step of the clotting process. This dimeric intermeidate is shown to be formed by the association of an intact fibrinogen molecule and a fibrin monomer devoid in only the peptide A, (b) Ca2+ enhances the proteolytic step as illustrated by the measure of the kinetics of H+ release at pH 8.6. On the basis of these observations it is proposed that Ca2+ catalyses the proteolysis of fibrinogen by thrombin through the formation of a Ca2+-dependent dimer.
mesh_terms: D000818:Animals; D001777:Blood Coagulation / Q000187:drug effects; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D005340:Fibrinogen / Q000378:metabolism; D007700:Kinetics; D011485:Protein Binding; D013917:Thrombin / Q000378:metabolism
chemical_list: D005340:Fibrinogen; D013917:Thrombin; D002118:Calcium