A transitional state of pro-urokinase that has a higher catalytic efficiency against glu-plasminogen than urokinase.

摘要: Abstract Plasminogen activation by single-chain urokinase-type plasminogen activator or pro-urokinase (pro-UK) is accompanied the generation of two-chain urokinase (UK) plasmin which provides a positive feedback. In present study, time course Glu-plasminogen and Lys-plasminogen (10 microM) pro-UK (1.0 nM) was studied. presence native (Glu-plasminogen), three distinct phases with different rates were observed. The initial phase slow corresponded to intrinsic activity as reflected plasmin-resistant mutant (Lys158----Ala). This followed second had most rapid rate. third rate significantly slower than paralleled UK nM). coincided at there only about 50% conversion UK, whereas final essentially complete conversion. fibrin fragment E-2 (20 microM), previously shown strongly promote pro-UK, identical phenomenon observed, but one-tenth concentration pro-UK. again transitional (25-60%) To further examine this phenomenon, controlled using kallikrein in inhibitor. experiment, bound solid-phase measured. A similar three-phase sequence highest coinciding 45% UK. mechanism for state postulated based on established higher affinity Glu-plasminogen. exceptional property proenzyme may enable transient be generated during transition from corresponding more favorable KM kcat hypothesis supported results experiments substituted Glu form. No consistent relatively high against Lys-plasminogen.