Tripeptidyl peptidases: enzymes that count

Tomkinson, Birgitta

doi:10.1016/s0968-0004(99)01435-8

Cited by 131 publications

(102 citation statements)

References 25 publications

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“…The major cytoplasmic proteolytic process in eukaryotes is the ubiquitin proteasome pathway leaving the cell with short peptides, ranging from 3 to 22 residues in length (Tomkinson, 1999 ;Kisselev et al, 1999). These peptides, and peptides resulting from the breakdown of protein substrates that are imported from the external milieu via peptide transporters, are further degraded to amino acids by tri-, di-, carboxy-and aminopeptidases.…”

Section: Introductionmentioning

confidence: 99%

Lysine aminopeptidase of Aspergillus niger The EMBL accession number for the sequence reported in this paper is AJ292570.

2001

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Conserved regions within the M1 family of metallo-aminopeptidases have been used to clone a zinc aminopeptidase from the industrially used fungus Aspergillus niger. The derived amino acid sequence of ApsA is highly similar to two yeast zinc aminopeptidases, LAPI and AAPI (53 3 and 50 9 % overall similarity, respectively), two members of the M1 family of metalloaminopeptidases. The encoding gene was successfully overexpressed in A. niger and the overexpressed product was purified and characterized. Aminopeptidase A was found to be active towards a number of amino acid p-nitroanilide (pNA) substrates, viz. K-pNA, R-pNA, L-pNA, M-pNA, A-pNA and F-pNA. The most preferred N-terminal amino acid is lysine and not leucine, arginine or alanine, the N-terminal amino acids preferred by the yeast homologues. The K m and K cat for K-pNA and L-pNA were 0 17 mM and 0 49 µkat mg N1 , and 0 16 mM and 0 31 µkat mg N1 , respectively. The pH optimum of the enzyme is between 7 5 and 8, whereas the enzyme is stable between pH 5 and 8. The enzyme is inhibited by the metal chelators EGTA, EDTA and 1,10-phenanthrolin. Bestatin was also able to inhibit the activity.

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Section: Introductionmentioning

confidence: 99%

Lysine aminopeptidase of Aspergillus niger The EMBL accession number for the sequence reported in this paper is AJ292570.

2001

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“…An Arabidopsis T-DNA mutant defective in TPP2 expression displays no phenotypic abnormalities and is not hypersensitive to either amino acid analogs or the 26S proteasome inhibitor MG132. As a consequence, plants likely contain other intermediate exopeptidases that assist in amino acid recycling.Proteolysis serves a variety of essential functions, including the elimination of misfolded or damaged proteins, the precise removal of regulatory proteins, and the maintenance of free amino acid pools needed for continual protein synthesis (Vierstra, 1996;Tomkinson, 1999). To facilitate this breakdown, plants and animals have evolved several proteolytic mechanisms for each subcellular compartment.…”

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confidence: 99%

“…Whereas the plant 26S proteasome and several exopeptidases that release single amino acids have been described biochemically (e.g. Callis, 1995;Gu et al, 1996), the endo/exopeptidases that fulfill these intermediate roles are not well known.In animals, tripeptidyl peptidase (TPP)II is an intermediate exopeptidase thought to be necessary for efficient protein turnover (EC 3.4.14.10;Tomkinson, 1999). This aminopeptidase was first identified as a Ser 2 These authors contributed equally to the paper.…”

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confidence: 99%

“…Proteolysis serves a variety of essential functions, including the elimination of misfolded or damaged proteins, the precise removal of regulatory proteins, and the maintenance of free amino acid pools needed for continual protein synthesis (Vierstra, 1996;Tomkinson, 1999). To facilitate this breakdown, plants and animals have evolved several proteolytic mechanisms for each subcellular compartment.…”

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Tripeptidyl Peptidase II. An Oligomeric Protease Complex from Arabidopsis

et al. 2005

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The breakdown of most nuclear and cytoplasmic proteins involves their partial cleavage by the 26S proteasome followed by further disassembly to free amino acids by the combined action of endo-and exopeptidases. In animals, one important intermediate exopeptidase is tripeptidyl peptidase (TPP)II, which digests peptide products of the 26S proteasome and other endopeptidases into tripeptides. Here, we describe the purification and characterization of TPPII from Arabidopsis (Arabidopsis thaliana). Like its animal counterparts, Arabidopsis TPPII exists as a soluble, approximately 5-to 9-MD complex. Two related species of 153 and 142 kD are present in the purified preparations that are derived from a single TPP2 gene. Sequencing by Edman degradation of the intact polypeptides and mass spectrometry of proteolytic fragments demonstrated that the 142-kD form mainly differs from the 153-kD form by a truncation at the C-terminal end. This serine protease is a member of the subtilisin superfamily and is sensitive to the inhibitors alanine-alanine-phenylalanine-chloromethylketone and butabindide, which are diagnostic for the TPPII subfamily. The Arabidopsis TPP2 gene is widely expressed in many tissue types with related genes evident in other plant genomes. Whereas the 26S proteasome is essential, TPPII appears not as important for plant physiology. An Arabidopsis T-DNA mutant defective in TPP2 expression displays no phenotypic abnormalities and is not hypersensitive to either amino acid analogs or the 26S proteasome inhibitor MG132. As a consequence, plants likely contain other intermediate exopeptidases that assist in amino acid recycling.Proteolysis serves a variety of essential functions, including the elimination of misfolded or damaged proteins, the precise removal of regulatory proteins, and the maintenance of free amino acid pools needed for continual protein synthesis (Vierstra, 1996;Tomkinson, 1999). To facilitate this breakdown, plants and animals have evolved several proteolytic mechanisms for each subcellular compartment. In the vacuole/lysosome, proteins are catabolized by a variety of proteases and peptidases following their delivery to this hydrolytic compartment via endocytic and autophagic mechanisms (Thompson and Vierstra, 2005). For nuclear and cytoplasmic proteins, as well as abnormal polypeptides transported in a retrograde fashion from the endoplasmic reticulum to the cytoplasm, a major route involves ubiquitin (Ub) and the 26S proteasome (Smalle and Vierstra, 2004). Here, proteins destined for degradation are selectively tagged by the covalent attachment of multiple Ubs.These ubiquitinated proteins are then recognized and cleaved into smaller fragments by the 26S proteasome, a self-compartmentalized ATP-dependent protease complex with broad substrate and cleavage specificity.Products of the 26S proteasome are predominantly peptides 6 to 12 amino acids in length (Wenzel et al., 1994;Kisselev et al., 1999;Voges et al., 1999). Complete recycling requires further cleavage of these peptides by intermediate...

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“…This enzyme specifically cleaves tripeptides from the amino-termini of partially unfolded proteins-it is literally, an 'enzyme that counts'. 5 TPP-1/CLN2 is the first example of the involvement of a lysosomal protease in a neurodegenerative storage disease. The major intact protein that is identified in the storage material in TPP-I deficiency is subunit c of mitochondrial ATP synthase.…”

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confidence: 99%