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 [PMID:7845208]. 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 [PMID:7845208].
Defined by 4 residues: TYR:A-473SER:A-554ASP:A-641HIS:A-680