Molecular basis of specific inhibition of urokinase plasminogen activator by amiloride

Cancer Biochem Biophys. 1999 Jul;17(1-2):109-23.


The urokinase plasminogen activator (uPA) and tissue plasminogen activator (tPA) are very similar serine proteases with the same physiological function, the activation of plasminogen. An increased amount or activity of uPA but not tPA has been detected in human cancers. The PAs are weak proteolytic enzymes, but they activate plasminogen to plasmin, a strong proteolytic enzyme largely responsible for the malignant properties of cancers. It has been shown recently that the administration of uPA inhibitors can reduce tumor size. Inhibitors of uPA could therefore be used as anti-cancer and anti-angiogenesis agents. It has been found that amiloride competitively inhibits the catalytic activity of uPA but not tPA. Modification of this chemical could therefore produce a new class of uPA specific inhibitors and a new class of anti-cancer agents. The X-ray structure of the uPA complex with amiloride is not known. There are structural differences in the specificity pocket of uPA and tPA. However, the potential energy of binding amiloride is lower outside this cavity in the case of tPA. A region responsible for binding amiloride to tPA has been proposed as the loop B93-B101, reached in negatively charged amino acids present in tPA but not uPA.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amiloride / chemistry
  • Amiloride / pharmacology*
  • Amino Acid Chloromethyl Ketones / chemistry
  • Amino Acid Sequence
  • Antineoplastic Agents / chemistry
  • Antineoplastic Agents / pharmacology*
  • Binding Sites / drug effects
  • Binding, Competitive
  • Catalysis / drug effects
  • Crystallography, X-Ray
  • Drug Design
  • Humans
  • Models, Molecular
  • Molecular Conformation
  • Molecular Sequence Data
  • Neoplasm Proteins / antagonists & inhibitors
  • Neoplasm Proteins / chemistry
  • Protein Binding
  • Protein Conformation
  • Protein Structure, Tertiary
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Serine Proteinase Inhibitors / chemistry
  • Serine Proteinase Inhibitors / pharmacology*
  • Substrate Specificity
  • Tissue Plasminogen Activator / chemistry
  • Tissue Plasminogen Activator / drug effects
  • Urokinase-Type Plasminogen Activator / antagonists & inhibitors*
  • Urokinase-Type Plasminogen Activator / chemistry
  • Water / chemistry


  • Amino Acid Chloromethyl Ketones
  • Antineoplastic Agents
  • Neoplasm Proteins
  • Serine Proteinase Inhibitors
  • glutamyl-glycyl-arginyl-chloromethyl ketone
  • Water
  • Amiloride
  • Tissue Plasminogen Activator
  • Urokinase-Type Plasminogen Activator