Lactacystin, a specific inhibitor of the proteasome, inhibits human platelet lysosomal cathepsin A-like enzyme

Halina Ostrowska, Cezary Wojcik, Satoshi Omura, Krzysztof Worowski

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Lactacystin, the most specific inhibitor of the proteasome, strongly inhibited at pH 5.5 the activity of human platelet lysosomal cathepsin A-like enzyme. At a concentration as low as 1-5 μM it almost completely decreased the hydrolysis rate of cathepsin A specific substrates: Cbz-Phe-Ala and FA-Phe-Phe. This inhibition was probably due to the lactacystin intermediate β-lactone formed during 10 min hydrolysis at pH 8.0 since nonhydrolyzed inhibitor did not affect cathepsin A activity. Basing on similarities in the inhibitor sensitivity, pH optimum, and substrate preferences it is suggested that the cathepsin A-like activity may be involved in chymotrypsin-like activity of the proteasome.

Original languageEnglish (US)
Pages (from-to)729-732
Number of pages4
JournalBiochemical and Biophysical Research Communications
Issue number3
StatePublished - May 29 1997


ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology

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