COMPETITION BETWEEN PLASMINOGEN AND PROCATHEPSIN-B AS A PROBE TO DEMONSTRATE THE IN-VITRO ACTIVATION OF PROCATHEPSIN B BY THE TISSUE-PLASMINOGEN ACTIVATOR

The tissue plasminogen activator (tPA) was found to activate in vitro the procathepsin B purified from malignant ascitic fluids, This activa tion was time and dose dependent, and was associated with the processi ng of procathepsin B. The present study shows that tPA is a fast activ ator of procathepsin B in a neutral pH range, such that generation of cathepsin B activity and processing of procathepsin B are achieved aft er a 5-min incubation time at 37 degrees C, pH 7.4, In contrast, compe tition between plasminogen and procathepsin B was observed for the act ivation and processing by tPA, From these findings, a plasminogen acti vator pathway for procathepsin B activation related to the plasminogen concentration may exist. In. vivo this pathway may be involved in a p roteolytic cascade linked to invasion and metastasis. (C) 1996 Academi c Press, Inc.