TY  - JOUR
PY  - 1997//
TI  - The suicide substrate reaction between plasminogen activator inhibitor 1 and thrombin is regulated by the cofactors vitronectin and heparin
JO  - Blood
A1  - van Meijer, M.
A1  - Smilde, A.
A1  - Tans, G.
A1  - Nesheim, M. E.
A1  - Pannekoek, H.
A1  - Horrevoets, A. J.
SP  - 1874
EP  - 1882
VL  - 90
IS  - 5
N2  - The interaction of thrombin with plasminogen activator inhibitor 1 (PAI-1) is shown to result in the simultaneous formation of both cleaved PAI-1 and a sodium dodecyl sulfate-stable thrombin-PAI-1 complex. The kinetics of this reaction can be described by a "suicide substrate" mechanism that includes a branched reaction pathway, which terminates in either the stable inhibitor-enzyme complex or the cleaved inhibitor plus free enzyme. Because of the branched pathway, approximately three moles of PAI-1 are needed to completely inhibit one mole of thrombin. Heparin and vitronectin enhance the rate of inhibition from 9.8 x 10(2) L mol(-1) s(-1) to 6.2 x 10(4) L mol(-1) s(-1) and 2.1 x 10(5) L mol(-1) s(-1), respectively, under optimal conditions. In addition to enhancing the rate of inhibition, both cofactors increase the apparent stoichiometry of the PAI-1-thrombin interaction, with cofactor concentration dependencies similar to the inhibition reaction. Thus, at 37 degrees C approximately six cleavage reactions occur per inhibition reaction. Therefore, thrombin will efficiently inactivate PAI-1 in the presence of either vitronectin or heparin, unless a sufficient excess of the inhibitor is present. These results show that physiological cofactors are able to switch a protease-serpin inhibition reaction to a substrate reaction, depending on the local concentrations of each of the components.<p /> <p>Language: en</p>
LA  - en
SN  - 0006-4971
UR  - http://dx.doi.org/
ID  - ref1
ER  -