Competition between Plasminogen and Procathepsin B as a Probe to Demonstrate thein VitroActivation of Procathepsin B by the Tissue Plasminogen Activator

The tissue plasminogen activator (tPA) was found to activatein vitrothe procathepsin B purified from malignant ascitic fluids. This activation was time and dose dependent, and was associated with the processing of procathepsin B. The present study shows that tPA is a fast activator of procathepsin B in a neutral pH range, such that generation of cathepsin B activity and processing of procathepsin B are achieved after a 5-min incubation time at 37°C, pH 7.4. In contrast, competition between plasminogen and procathepsin B was observed for the activation and processing by tPA. From these findings, a plasminogen activator pathway for procathepsin B activation related to the plasminogen concentration may exist.In vivothis pathway may be involved in a proteolytic cascade linked to invasion and metastasis.