Fig. 2.

Effects of a ¹⁷⁹RHRGGS¹⁸⁴→¹⁷⁹AAAAAA¹⁸⁴ urokinase mutant (ΔDS-uPA) on the rate of interaction with plasminogen activator inhibitor-1 (PAI-1) and activation of Glu-plasminogen. A: dependence of the observed first-order rate constants (k_obs) for the interaction of PAI-1 with wild-type urokinase (wt-uPA; ○) and ΔDS-uPA (△) on enzyme concentration. The data for wt- and ΔDS-uPA are shown in different scales. The values of k_obs were determined as previously described (45, 49, 51). Linear equations were fit (solid lines; r² > 0.95) to the data, and values of the second-order association rate constant (k_ass) were determined from the slopes. The ratio of k_ass for wt-uPA over ΔDS-uPA was 63.0 for inhibition by PAI-1. B: dependence of the rates of accumulation of plasmin due to activation of Glu-plasminogen by wt-uPA (○) and ΔDS-uPA (△) on enzyme concentration. The rates of plasmin accumulation were determined from the slopes of linear equations, which were fit (solid lines; r² > 0.99) to the data as described previously (49). The ratio of slopes for wt-uPA over ΔDS-uPA for activation of Glu-plasminogen was 1.5. AU, arbitrary units.