Inhibition of Recombinant Human Blood Coagulation Factor VIIa Amidolytic and Proteolytic Activity by Zinc Ions

Abstract

Although it is well established that calcium is an essential cofactor in blood coagulation, recent experimental evidence suggests that zinc may also play an important role in hemostasis. In the present study, we have examined the effect of zinc ions on the amidolytic and proteolytic activity of recombinant factor VIIa in the presence of physiological levels of calcium ions. The amidolytic activity of factor VIIa was inhibited half-maximally by 20 microM zinc. The amidolytic activity of a derivative of factor VIIa lacking the gamma-carboxyglutamic acid domain was also inhibited half-maximally by 20 microM zinc, suggesting that the mechanism of zinc inhibition of factor VIIa amidolytic activity did not involve its gamma-carboxyglutamic acid residues. The amidolytic activity of a complex of recombinant tissue factor and factor VIIa was inhibited half-maximally by 70 microM zinc. In contrast to the results obtained with factor VIIa, the amidolytic activities of other human vitamin K-dependent coagulation proteases including factor Xa, thrombin and activated protein C were not appreciably affected by 50-100 microM zinc. The proteolytic activation of factor X by a complex of factor VIIa and relipidated tissue factor apoprotein was inhibited half-maximally by 40 microM zinc, whereas activation of factor IX in this system was inhibited half-maximally by 70 microM zinc ions. Considerably higher levels of zinc (approximately 100 microM) were required to inhibit half-maximally the rate of factor X activation by a complex of factor VIIa and functional tissue factor on the surface of either a human bladder carcinoma cell line, J82, or stimulated human umbilical vein endothelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)