| Type: | Domain | Name: | Peptidase S9, prolyl oligopeptidase, catalytic domain |
| Description: | Proteolytic enzymes that exploit serine in their catalytic activity are ubiquitous, being found in viruses, bacteria and eukaryotes []. They include a wide range of peptidase activity, including exopeptidase, endopeptidase, oligopeptidase and omega-peptidase activity. Many families of serine protease have been identified, these being grouped into clans on the basis of structural similarity and other functional evidence []. Structures are known for members of the clans and the structures indicate that some appear to be totally unrelated, suggesting different evolutionary origins for the serine peptidases [].Not withstanding their different evolutionary origins, there are similarities in the reaction mechanisms of several peptidases. Chymotrypsin, subtilisin and carboxypeptidase C have a catalytic triad of serine, aspartate and histidine in common: serine acts as a nucleophile, aspartate as an electrophile, and histidine as a base []. The geometric orientations of the catalytic residues are similar between families, despite different protein folds []. The linear arrangements of the catalytic residues commonly reflect clan relationships. For example the catalytic triad in the chymotrypsin clan (PA) is ordered HDS, but is ordered DHS in the subtilisin clan (SB) and SDH in the carboxypeptidase clan (SC) [, ].This domain covers the active site serine of the serine peptidases belonging to MEROPS peptidase family S9 (prolyl oligopeptidase family, clan SC). The protein fold of the peptidase domain for members of this family resembles that of serine carboxypeptidase D, the type example of clan SC. Examples of protein families containing this domain are:Prolyl endopeptidase () (PE) (also called post-proline cleaving enzyme). PE is an enzyme that cleaves peptide bonds on the C-terminal sideof prolyl residues. The sequence of PE has been obtained from a mammalian species (pig) and from bacteria (Flavobacterium meningosepticumand Aeromonas hydrophila); there is a high degree of sequence conservation between these sequences.Escherichia coliprotease II () (oligopeptidase B) (gene prtB) which cleaves peptide bonds on the C-terminal side of lysyl and argininylresidues.Dipeptidyl peptidase IV () (DPP IV). DPP IV is an enzyme that removes N-terminal dipeptides sequentially from polypeptides havingunsubstituted N-termini provided that the penultimate residue is proline.Saccharomyces cerevisiae(Baker's yeast) vacuolar dipeptidyl aminopeptidases A and B (DPAP A and DPAP B), encoded by the STE13 and DAP2 genes respectively. DPAP A is responsible for the proteolytic maturation of the alpha-factor precursor.Acylamino-acid-releasing enzyme () (acyl-peptide hydrolase). This enzyme catalyses the hydrolysis of the amino-terminal peptide bond ofan N-acetylated protein to generate a N-acetylated amino acid and a protein with a free amino-terminus.These proteins belong to MEROPS peptidase families S9A, S9B and S9C. | Short Name: | Peptidase_S9 |
