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

• Published in: FEBS letters Vol. 500; no. 3; pp. 145 - 148
• Main Authors: Warburton, Michael J, Bernardini, Francesca
• Format: Journal Article
• Language: English
• Published: England Elsevier B.V 06-07-2001
• Subjects: Amino Acid Substitution; Aminopeptidases; Angiotensin II - analogs & derivatives; Angiotensin II - chemistry; Angiotensin II - drug effects; Angiotensin-II; Animals; Catalysis; Chromatography, High Pressure Liquid; Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; Endopeptidases - chemistry; Endopeptidases - pharmacology; Hydrogen-Ion Concentration; Lysosomal peptide degradation; Lysosomes - enzymology; MALDI-TOF-MS, matrix-assisted laser desorption ionisation-time of flight-mass spectrometry; Neuronal Ceroid-Lipofuscinoses - enzymology; NHMec, -methylcoumarylamide; Peptides - chemistry; Peptides - drug effects; Serine Proteases; Structure-Activity Relationship; Substrate Specificity - physiology; Swine; TFA, trifluoroacetic acid; TPP-I, tripeptidyl peptidase-I; Tripeptidyl peptidase-I; TPP-I, tripeptidyl peptidase-I; Tripeptidyl peptidase-I; Lysosomal peptide degradation; MALDI-TOF-MS, matrix-assisted laser desorption ionisation-time of flight-mass spectrometry; Angiotensin-II; NHMec, -methylcoumarylamide; TFA, trifluoroacetic acid
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/S0014-5793(01)02608-4

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 P
1 and P
1′ 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 P
1 and P
1′ positions,
K
cat/
K
m values varying only 5-fold for a range of substitutions. However, Pro or Lys in the P
1 position and Pro in the P
1′ 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.