Thrombin and plasmin-like activities in the latices of Cryptostegia grandiflora and Plumeria rubra.

Latex proteins have drawn attention because they have shown several pharmacological activities. Herein, the fibrin(ogen)olytic activity of Cryptostegia grandiflora (CgLP) and Plumeria rubra (PrLP) latices were evaluated and characterized. Ion-exchange chromatography separated CgLP in proteolytic (CgLP PI) and nonproteolytic proteins (CgLP PII). CgLP and CgLP PI hydrolyzed azocasein in a dose-dependent manner, whereas CgLP PII and PrLP showed negligible activities. CgLP and CgLP PI accelerated plasmatic clot formation and digested all fibrinogen chains in a time/dose-dependent manner, though in a nonspecific way. CgLP and CgLP PI did not fully hydrolyze the subunits of the fibrin clot since fibrin α-chain showed resistance to proteolysis. No fibrinogenolytic activity was noticed after incubation of CgLP and CgLP PI with E-64. These results suggested that fibrinogenolytic and procoagulant activities of C. grandiflora were performed by cysteine proteases and confirm the activity of latex cysteine proteases as thrombin and plasmin-like proteins.