Fluorogenic substrates for sensitive and differential estimation of urokinase and tissue plasminogen activator

Two fluorogenic peptide amides have been synthesized, i.e. BOC-L-valyl-glycyl-L-arginine 2-naphthylamide (I) and L-valyl-glycyl-L-arginine 2-naphthylamide (II). The kinetic parameters of plasmin, urokinase and human uterine tissue plasminogen activator on substrates I and II have been determined. Quite unexpectedly, the tissue activator appeared to require for its activity a blocked amino terminus on the substrate. This was further corroborated with other synthetic substrates. Plasmin and urokinase did not show this requirement.