Is the Action of Calcium in the Coagulation of Blood Stoichiometric or Catalytic?

Abstract

By determining the amt. of thrombin formed from known amts. of Ca, it can be detd. whether the action of the latter is catalytic or stoichiometric. The Ca cone, is controlled accurately by adding known amts. to plasma obtained from blood decalcified by passage through Amberlite. Thrombin is estimated by allowing plasma to clot and then finding the amt. of prothrombin remaining. The relation of Ca cone, to thrombin production is stoichiometric. When the CaCl2 cone, in plasma is 0.00015 [image] or lower, very little prothrombin is converted to thrombin in an hr., although other conditions are optimum. The small amt. of thrombin formed coagulates all the fibrinogen because it acts enzymatically. If Ca acted catalytically, it would similarly change all the prothrombin to thrombin. The findings suggest that the reactions which produce thrombin are chemical and not enzymatic.