Peptidase S26B (IPR001733)

Short name: Peptidase_S26B

Overlapping homologous superfamilies

Family relationships


Proteolytic enzymes that exploit serine in their catalytic activity are ubiquitous, being found in viruses, bacteria and eukaryotes [PMID: 7845208]. 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 [PMID: 7845208]. 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 [PMID: 7845208].

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 [PMID: 7845208]. The geometric orientations of the catalytic residues are similar between families, despite different protein folds [PMID: 7845208]. 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) [PMID: 7845208, PMID: 8439290].

This group of serine peptidases belong to MEROPS peptidase family S26 (signal peptidase I family, clan SF), subfamily S26B.

Eukaryotic microsomal signal peptidase is involved in the removal of signal peptides from secretory proteins as they pass into the endoplasmic reticulum lumen [PMID: 7845208]. The peptidase is more complex than its mitochondrial and bacterial counterparts, containing a number of subunits, ranging from two in the chicken oviduct peptidase, to five in the dog pancreas protein [PMID: 7845208]. They share sequence similarity with the bacterial leader peptidases (family S26A), although activity here is mediated by a serine/histidine dyad rather than a serine/lysine dyad [PMID: 7845208]. Archaeal signal peptidases also belong to this group.

GO terms

Biological Process

GO:0006465 signal peptide processing

Molecular Function

GO:0008233 peptidase activity

Cellular Component

GO:0016020 membrane

Contributing signatures

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