Differential reactivity of Glu‐Gly‐Arg‐CH2Cl, a synthetic urokinase inhibitor, with single‐chain and two‐chain forms of urokinase‐type plasminogen activator

Abstract

Glu‐Gly‐Arg‐CH2Cl, a synthetic inhibitor which alkylates the active‐site histidine of urokinase with an apparent second‐order rate constant of approximately 104M−1s−1, reacts differently with single‐chain and two‐chain forms of urokinase‐type plasminogen activators (scu‐PA and tcu‐PA). Kinetic analysis indicated that the plasminogen activating potential of tcu‐PA is irreversibly inhibited in a two‐step reaction according to (Formula Presented.) with K1= 5.0 × 10−6M and K2= 0.05 s−1. The plasminogen‐activating potential of scu‐PA, however, is competitively inhibited by Glu‐Gly‐Arg‐CH2Cl with Ki= 1.3 × 10−6 M. Reversibility of the interaction of Glu‐Gly‐Arg‐CH2Cl with scu‐PA was confirmed by the restoration of full enzymatic activity after removal of inhibitor. The differential interaction of Glu‐Gly‐Arg‐CH2Cl with scu‐PA and tcu‐PA supports the hypothesis that these molecular forms of urokinase‐type PA have intrinsically different enzymatic properties. Copyright © 1987, Wiley Blackwell. All rights reserved