The specificity of lysosomal tripeptidyl peptidase‐I determined by its action on angiotensin‐II analogues

FEBS Letters

Warburton, Michael J¹  Bernardini, Francesca¹ 

[1] Department of Cellular Pathology, St George's Hospital Medical School, Cranmer Terrace, London SW17 0RE, UK

关键词: Tripeptidyl peptidase-I;    Lysosomal peptide degradation;    Angiotensin-II;    TFA;    trifluoroacetic acid;    TPP-I;    tripeptidyl peptidase-I;    MALDI-TOF-MS;    matrix-assisted laser desorption ionisation-time of flight-mass spectrometry;    -NHMec;    -methylcoumarylamide;   

DOI  :  10.1016/S0014-5793(01)02608-4

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Tripeptidyl peptidase-I (TPP-I) is a lysosomal peptidase which cleaves tripeptides from the N-terminus of peptides. The function of the enzyme is unclear but its importance is demonstrated by the fact that mutations in TPP-I are responsible for late infantile neuronal ceroid lipofuscinosis, a lethal lysosomal storage disease. As a step towards identifying its natural substrates, we have used a series of synthetic peptides, based on angiotensin-II, to explore the effects of peptide chain length and the effects of amino acid substitutions at the P₁ and P₁′ positions on the rate of catalysis. With the exception of angiotensin-(1–8) (angiotensin-II), which is a relatively poor substrate for TPP-I, the rate of catalysis increases with increasing chain length. K _cat/K _m values increase 50-fold between angiotensin-(1–5) and angiotensin-(1–14). TPP-I shows little specificity for the nature of the amino acids in the P₁ and P₁′ positions, K _cat/K _m values varying only 5-fold for a range of substitutions. However, Pro or Lys in the P₁ position and Pro in the P₁′ positions are incompatible with TPP-I activity. These observations suggest that TPP-I is a non-specific, but essential, peptidase involved in the latter stages of lysosomal protein degradation.

【 授权许可】

Unknown