Effect of Divalent Cations on Proteolysis of Fibrinogen.

Abstract

The effects of various divalent cations on proteolysis of fibrinogen by trypsin and chymotrypsin were studied. Mg, Mn, Co, Zn, and Cd were approximately equally effective in reducing the rate of proteolysis by trypsin. At levels as low as 10-7 [image], Ca began to decrease the rate of proteolysis by either trypsin or chymotrypsin, and a 50% reduction of the rate occurred at about 1-3 [image]. The effects of Ca on both tryptic and chymotryptic digestion appeared to yield the kinetics of a competitive inhibition; and the suggestion is made that Ca acts to affect an equilibrium between two forms of fibrinogen, the one susceptible, the other inhibitory, to proteolysis.