Kinetics of the activation of bovine coagulation factor X by components of the extrinsic pathway. Kinetic behavior of two-chain factor VII in the presence and absence of tissue factor

S.A Silverberg,Y Nemerson,M Zur

doi:10.1016/s0021-9258(19)75245-4

Abstract

Kinetics of the activation of bovine coagulation factor X by components of the extrinsic pathway. Kinetic behavior of two-chain factor VII in the presence and absence of tissue factor

Highlights

A new assay for the activation of bovine coagulation Factor X by two-chain Factor VII is described
Comparison of the kinetic parameters obtained in 10 mM benzamidine in the presence and absence of tissue factor shows that the co-factor decreases the K, IO-fold and increases kc, 2,900-fold
In the presence of Factor VII, tissue factor, and Ca2+, Factor X is cleaved in the NH

Summary

Introduction

A new assay for the activation of bovine coagulation Factor X by two-chain Factor VII (cu-VIIa) is described. The sensitivity of the assay is great enough to detect hydrolysis of Factor X by cY-VIIa in the absence of tissue factor, which is 8,000-fold slower than with the cofactor present at a Factor X concentration of 100 pg/ml (1.8 pm). These experiments were performed using benzamidine to inhibit the feedback reactions of the product, Factor Xa. benzamidine inhibits cy-VIIa activity to some degree, which we show occurs with a mixed competitive and uncompetitive mechanism. In the presence of Factor VII, tissue factor, and Ca2+, Factor X is cleaved in the NH,-

Methods

Results

Conclusion