Characterization of a plasminogen activator produced by Acanthamoeba castellanii

MonaLisa M. Mitra, Hassan Alizadeh, Robert D. Gerard, Jerry Y. Niederkorn

Research output: Contribution to journalArticlepeer-review

50 Scopus citations


Serine proteases play an important role in a diverse array of biological processes, including embryogenesis, metastasis, angiogenesis, thrombolysis and tissue invasion by certain parasites. The latter observation prompted us to explore the possibility that the tissue-invasive ocular parasite Acanthamoeba castellanii elaborates one or more serine proteases. Acanthamoeba sp. are pathogenic free-living amoebae that can produce an invasive, blinding inflammatory disease of the cornea, termed Acanthamoeba keratitis. The present study reports the preliminary purification and characterization of a novel plasminogen activator from an ocular isolate of A. castellanii. The parasite-derived enzyme has a molecular mass of approx. 40 kDa and produces a single band of lysis on fibrinogen-agarose zymographs. Activity of the enzyme is completely inhibited by treatment with diisopropylfluorophosphate, indicating that it is a serine protease. The parasite-derived serine protease is not inhibited by amiloride which is a strong inhibitor of urokinase-type plasminogen activator. Additionally, the enzyme is not inhibited by plasminogen activator inhibitor-1 which is the primary physiological inhibitor of both urokinase and tissue-type plasminogen activator. It does not cross-react with antibodies specific for human urokinase or tissue-type plasminogen activator. The parasite-derived enzyme activates plasminogen from several mammalian species, including human, cow and pig. Thus, it is possible that this parasite-derived serine protease contributes to the pathogenesis of Acanthamoeba keratitis.

Original languageEnglish (US)
Pages (from-to)157-164
Number of pages8
JournalMolecular and Biochemical Parasitology
Issue number1-2
StatePublished - Jul 1995


  • Acanthamoeba
  • Keratitis
  • Pathogenic
  • Plasminogen activator
  • Serine protease

ASJC Scopus subject areas

  • Parasitology
  • Molecular Biology


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