Enhancement of plasminogen binding and fibrinolysis by chloropeptin I

Plasminogen is a zymogen of the fibrinolytic serine protease, plasmin. Plasminogen binds, through its lysine binding sites in the kringle domain, to blood and vascular cells or fibrin, where it is efficiently activated and exerts fibrinolytic activity (1,2). We have recently found that complestatin, a peptide-like metabolite of streptomyces (3,4), enhances plasminogen binding to U937 cells and fibrin, thus potentiating fibrinolysis (5). In the present study, complestatin was found to be converted by an acid treatment to a more active isomer in enhancing plasminogen binding to U937 cells. This isomer was identified to be chloropeptin I, which was recently isolated from a culture of Streptomyces sp. by Matsuzaki et al. as an inhibitor of gp 120-CD4 binding (6). The present paper deals with the stimulation of fibrinolysis by chloropeptin I.