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Biochem Biophys Res Commun. 1997 May 29;234(3):729-32.

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

Author information

1
Department of Instrumental Analysis, Medical Academy, Bialystok, Poland.

Abstract

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 microM 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 beta-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.

PMID:
9175783
DOI:
10.1006/bbrc.1997.6434
[Indexed for MEDLINE]

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