Urokinase-type plasminogen activator is a strong plasminogen activator which specifically cleaves the proenzyme/zymogen plasminogen to form the active enzyme plasmin. It specifically catalyzes the cleavage of the arg-|-val bond in plasminogen. The active plasmin is then able to break down the fibrin polymers of blood clots. Clinically, urokinase-type plasminogen activator is given to patients suffering from thrombolytic disorders.
The amino terminal fragment (ATF) of urokinase-type plasminogen activator is 130 amino acid residues long. It consists of 2 alpha-helices (green) and 2 antiparallel beta-strands (purple). The ATF contains 2 domains; a growth factor domain and a kringle domain. It binds fucose (magenta) as a ligand. Fucose is a deoxy sugar, a monosaccharide with one or more hydroxyl (-OH) groups replaced by a hydrogen (-H). The formula for fucose is C6H12O6. The ATF also contains 6 disulfide bonds (blue) and are as follows: Cys11-Cys19, Cys13-Cys31, Cys33-Cys42, Cys50-Cys131, Cys71-Cys113, and Cys102-Cys126.