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The effect of analogues of chymostatin on lysosomal and non-lysosomal components of protein degradation in isolated hepatocytes.

Authors
Type
Published Article
Journal
Biochimica et Biophysica Acta
0006-3002
Publisher
Elsevier
Publication Date
Volume
925
Issue
2
Pages
185–193
Identifiers
PMID: 2887208
Source
Medline
License
Unknown

Abstract

Of the proteinase inhibitors derived from Streptomyces spp., chymostatin is the most effective inhibitor of non-lysosomal proteolysis. As part of a systematic study of the structural features of the chymostatin molecule that are responsible for this inhibitory activity, a series of fifteen di- and tripeptide analogues of chymostatin were tested for their ability to suppress protein degradation in isolated primary hepatocytes. Protein degradation was assessed in two ways: by the release of radiolabel from proteins prelabelled in vivo (to which both lysosomal and non-lysosomal processes contribute) and by the rate of inactivation of tyrosine aminotransferase, a process that is exclusively non-lysosomal. All inhibitors were relatively non-toxic and did not affect the intracellular ATP levels, although some suppression of gluconeogenesis was observed in the presence of leupeptin, chymostatin or the analogues. Tripeptide phenylalanine aldehydes or semicarbazones were at least as effective as chymostatin in reducing protein degradation, whereas peptide alcohols were relatively ineffective. Replacement of the basic capreomycidine moiety in chymostatin with an arginine residue improved the inhibitory activity but equally, substitution of the arginine residue with an uncharged norleucine residue was without significant effect. The structural features that are optimal for inhibition of chymotrypsin or other serine proteinases (previously defined) are not as critical for inhibition of protein degradation in vivo.

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