Effect of plasminogen on the plasminogen activator activity of scuPA/suPAR. Increasing concentrations of Glu-plasminogen (♦), Lys-plasminogen (□), and mini-plasminogen (▪) were incubated with scuPA (5 nM), suPAR (5 nM), and the plasmin chromogenic substrate (0.5 mM), and the OD at 405 nm was measured continuously over the next 20 minutes. The data are expressed as change in OD per minute.