Effect of active site-modified thrombin on the hydrolysis of platelet-
associated glycoprotein V by native thrombin
CL Knupp and GC White
To determine the relationship between equilibrium binding of thrombin to
sites on the platelet surface and the cleavage of membrane glycoprotein V
(GPV) by thrombin, we examined the effect of active site- modified thrombin
(1-chloro-3-tosylamido-7-amino-L-2-heptanone thrombin toslysCH2-thrombin)
on the binding of native thrombin to platelets and on the hydrolysis of GPV
by native thrombin. ToslysCH2-thrombin inhibited binding of native thrombin
to high affinity sites on the platelet surface. In contrast, hydrolysis of
GPV by native thrombin, even at threshold thrombin concentrations, was not
inhibited by pretreatment with toslysCH2-thrombin at concentrations up to
210 nmol/L. ToslysCH2-thrombin also had no appreciable effect on platelet
aggregation or release of 14C-serotonin induced by native thrombin. Because
toslysCH2-thrombin does not inhibit platelet release, aggregation, or GPV
hydrolysis by native thrombin but does inhibit high affinity surface
binding by native thrombin, these results indicate that thrombin binding
and hydrolysis of GPV are separate and unrelated events.
Volume 65,
Issue 3,
pp. 578-583,
03/01/1985
Copyright © 1985 by The American Society of Hematology
