Identification of prolylcarboxypeptidase as the cell matrix-associated prekallikrein activator

Investigations determined that the cell matrix-associated prekallikrein (PK) activator is prolylearboxypeptidase. PK activation on human umbilical vein endothelial cell (HUVEC) matrix is inhibited by antipain (IC50 = 50 muM) but not antifactor XIIa antibody, 3 mM benzamidine, 5 mM iodoacetic acid or iodoacetamide, or 3 mM N-ethylmaleimide. Corn trypsin inhibitor (IC50 = 100 nM) or Fmoc-aminoacylpyrrolidine-2-nitrile (IC50 = 100 muM) blocks matrix-associated PK activation. Angiotensin II (IC50 = 100 muM) or bradykinin (IC50 = 3 mM), but not angiotensin 1-7 or bradykinin 1-5, inhibits matrix-associated PK activation. ECV304 cell matrix PK activator also is blocked by 100 muM angiotensin II, 1 muM corn trypsin inhibitor, and 50 muM antipain, but not angiotensin 1-7. 1 mM angiotensin 11 or 300 muM Fmoc-aminoacylpyrrolidine-2-nitrile indirectly blocks plasminogen activation by inhibiting kallikrein formation for single chain urokinase activation. On immunoblot, prolylcarboxypeptidase antigen is associated with HUVEC matrix. These studies indicate that prolylearboxypeptidase is the matrix PK activator. (C) 2002 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.