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 language||English (US)|
|Number of pages||4|
|Journal||Biochemical and Biophysical Research Communications|
|State||Published - May 29 1997|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology