BINDING OF CALCIUM TO FIBRINOGEN - INFLUENCE ON THE CLOTTING PROCESS

The influence of Ca2+ on the basic reaction between thrombin and fibrinogen was investigated. The results demonstrate that: 1. (a)|A Ca2+-dependent dimeric intermediate is formed during the early step of the clotting process. This dimeric intermediate is shown to be formed by the association of an intact fibrinogen molecule and a fibrin monomer devoid in only the peptide A, 2. (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. © 1979.