Role of charged groups in factor XI/XIa activity.

K Morgan,S Schiffman

doi:10.1016/s0021-9258(18)33755-4

Abstract

To elucidate the role of charged groups in expression of factor XI coagulant activity, the charged groups of purified human blood coagulation factor XI/XIa containing 125I-XI/XIa were derivatized: free amino groups by succinylation, guanido groups of arginine by reaction with phenylglyoxal hydrate, and free carboxyl groups by reaction with ethylenediamine. The modified proteins were tested for: 1) ability to adsorb to glass, 2) ability to be cleaved by trypsin or factor XII-high molecular weight kininogen, 3) coagulant activity. The amino group-modified factor XI had a significantly decreased ability to bind to glass; modification of arginine or carboxyl groups did not affect adsorption. Trypsin cleaved factor XI with modified free amino, guanido, or carboxyl groups. Factor XII-high molecular weight kininogen could cleave only the arginine-modified factor XI. Amino group-modified factor XI and carboxyl group-modified factor XI lost all their factor XI assay activity, whereas arginine-modified factor XI retained 50% of the original activity. Amino group-modified factor XI could not be activated by trypsin, but arginine-modified and carboxyl group-modified factor XI could be activated by trypsin to 50% of the original activity. Succinylation of the amino groups of factor XIa destroyed all its factor XIa activity. Arginine-modified and carboxyl group-modified factor XIa retained 50% of their factor XIa activity. We conclude that epsilon-amino groups are essential for adsorption; activation by factor XII-high molecular weight kininogen requires free amino and carboxyl but not guanido groups; free amino, carboxyl, and guanido groups in factor XIa all appear to be critical for interaction of factor XIa with factor IX.

Highlights

Factor XIa in the presence of calcium ions catalyzes the activation of factor IX whichleads to subsequent clot formation [11, 17, 18].there are three separate steps in which factor XI in plasma participates in order to fully expressits coagulant activity: adsorptionat the activating surface, proteolyticcleavagetofactorXIa, and activation of factor IX by factorXIa
We evaluate the role of the charged groupsof lysine, aspartic and XIA. mino group-modified factor XI and carboxyl glutamic acids, andarginine in each of these aspects of factor group-modified factor XI lost all their factor XI assay XI activity
Amino group-modifiedfactor XI could not be activated by trypsin, but argininemodified and carboxyl group-modified factor XI could be activated by trypsin to 50% of the original activity

Summary

Kengathevy Morgan and Sandra Schiffman

From the Departments of Medicine and Biochemistry, University of Southern California School of Medicine, Los Angeles, California 90033. Factor XI-high molecular weight kininogen could cleave onltyhe arginine-modifiedfactor molecular weight of about 46,000 containing the surface adsorption sites [13] a n d a light chain of molecular weight of about 37,000 containing the active site [2,3]I.n the laboratory, activation cleavage can be catalyzed by trypsin in the absence of factor XII, HMWK’ or surface [1, 5, 15, 16]. Amino group-modifiedfactor XI could not be activated by trypsin, but argininemodified and carboxyl group-modified factor XI could be activated by trypsin to 50% of the original activity.

MATERIALS AND METHODS

Modification ofthe Free Amino Group of Lysine in Factor

Factor XII activation of factor XIor its derivatives was carried

Factor XI

Modification time rnin

Findings

DISCUSSION