“…we have shown in vitro (11,12) and in vivo (Fig.a) that recombinant plasminogen c( ^)' chain/t-PA ccB)) chain hybrid plasminogen activators are inhibited rapidly by plasma protease inhibitors, in particular by alpha2-antiplasmin (11, lz). The precise mechanism of inhibition is not clear, but it is likely to be similar to the mechanism of plasmin inhibiton by alpha2-antiplasmin, that is a rapid, primary, reversible interaction with the lysine-binding sites on the kringle domains of the plasmin A chain, followed by a secondary slower, covalent interaction with the active site of the B chain (25).…”