Human tissue kallikreins 3 and 5 can act as plasminogen activator releasing active plasmin.

Human tissue kallikreins (KLKs) are a group of serine proteases found in many tissues and biological fluids and are differentially expressed in several specific pathologies. Here, we present evidences of the ability of these enzymes to activate plasminogen. Kallikreins 3 and 5 were able to induce plasmin activity after hydrolyzing plasminogen, and we also verified that plasminogen activation was potentiated in the presence of glycosaminoglycans compared with plasminogen activation by tPA. This finding can shed new light on the plasminogen/plasmin system and its involvement in tumor metastasis, in which kallikreins appear to be upregulated.