| Type: | Family | Name: | Peptidase S9A, prolyl oligopeptidase |
| 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 group of serine peptidases belong to MEROPS peptidase family S9 (clan SC), subfamily S9A (prolyl oligopeptidase). The active site of members of this clan consists of a linear arrangement of serine, histidine and threonine catalytic residues []. Prolyl oligopeptidases are either located in the cytosol or they are membrane bound, where they cleave peptide bonds with prolyl P1 specificities (but cleavage of alanyl bonds has been detected). The proline must adopt a trans configuration within the chain. Peptides of up to 30 residues are cleaved []. | Short Name: | Peptidase_S9A |
