Peptidase M20B, tripeptide aminopeptidase (IPR010161)

Short name: Peptidase_M20B

Overlapping homologous superfamilies


Family relationships

  • Peptidase M20 (IPR002933)
    • Peptidase M20B, tripeptide aminopeptidase (IPR010161)


This entry represents metallopeptidases belonging to MEROPS peptidase family M20 (clan MH), subfamily M20B. They are tripeptide aminopeptidases commonly known as Peptidase T. PepT acts only on tripeptide substrates. It catalyzes the release of N-terminal amino acids with hydrophobic side chains from tripeptides with high specificity; dipeptides, tetrapeptides or tripeptides with the N terminus blocked are not cleaved [PMID: 11856302].

Over 70 metallopeptidase families have been identified to date. In these enzymes a divalent cation which is usually zinc, but may be cobalt, manganese or copper, activates the water molecule. The metal ion is held in place by amino acid ligands, usually three in number. In some families of co-catalytic metallopeptidases, two metal ions are observed in crystal structures ligated by five amino acids, with one amino acid ligating both metal ions. The known metal ligands are His, Glu, Asp or Lys. At least one other residue is required for catalysis, which may play an electrophillic role. Many metalloproteases contain an HEXXH motif, which has been shown in crystallographic studies to form part of the metal-binding site [PMID: 7674922]. The HEXXH motif is relatively common, but can be more stringently defined for metalloproteases as 'abXHEbbHbc', where 'a' is most often valine or threonine and forms part of the S1' subsite in thermolysin and neprilysin, 'b' is an uncharged residue, and 'c' a hydrophobic residue. Proline is never found in this site, possibly because it would break the helical structure adopted by this motif in metalloproteases [PMID: 7674922].

GO terms

Biological Process

GO:0006518 peptide metabolic process

Molecular Function

GO:0045148 tripeptide aminopeptidase activity
GO:0008270 zinc ion binding

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.