Pathways & interactions
Aspartic peptidase A1 family (IPR001461)
Short name: Aspartic_peptidase_A1
Overlapping homologous superfamilies
- Aspartic peptidase domain superfamily (IPR021109)
Peptidase family A1, also known as the pepsin family, contains peptidases with bilobed structures [PMID: 2115088, PMID: 2115087]. The two domains most probably evolved from the duplication of an ancestral gene encoding a primordial domain [PMID: 24179]. The active site is formed from an aspartic acid residue from each domain. Each aspartic acid occurs within a motif with the sequence D(T/S)G(T/S). Exceptionally, in the histoaspactic peptidase from Plasmodium falciparum, one of the Asp residues is replaced by His [PMID: 11782538]. A third essential residue, Tyr or Phe, is found on the N-terminal domain only in a beta-hairpin loop known as the "flap"; this residue is important for substrate binding, and most members of the family have a preference for a hydrophobic residue in the S1 substrate binding pocket. Most members of the family are active at acidic pH, but renin is unusually active at neutral pH. Family A1 peptidases are found predominantly in eukaryotes (but examples are known from bacteria [PMID: 19758436, PMID: 21749650]). Currently known eukaryotic aspartyl peptidases and homologues include the following:
- Vertebrate gastric pepsins A (EC:184.108.40.206), gastricsin (EC:220.127.116.11, also known pepsin C), chymosin (EC:18.104.22.168; formerly known as rennin), and cathepsin E (EC:22.214.171.124). Pepsin A is widely used in protein sequencing because of its limited and predictable specificity. Chymosin is used to clot milk for cheese making.
- Lysosomal cathepsin D (EC:126.96.36.199).
- Renin (EC:188.8.131.52) which functions in control of blood pressure by generating angiotensin I from angiotensinogen in the plasma.
- Memapsins 1 (EC:184.108.40.206; also known as BACE 2) and 2 (EC:220.127.116.11; also known as BACE) are membrane-bound and are able to perform one of the two cleavages (the beta-cleavage, hence they are also known as beta-secretases) in the beta-amyloid precursor to release the the amyloid-beta peptide, which accumulates in the plaques of Alzheimer's disease patients.
- Fungal peptidases such as aspergillopepsin A (EC:18.104.22.168), candidapepsin (EC:22.214.171.124), mucorpepsin (EC:126.96.36.199; also known as Mucor rennin), endothiapepsin (EC:188.8.131.52), polyporopepsin (EC:184.108.40.206), and rhizopuspepsin (EC:220.127.116.11) are secreted for sapprophytic protein digestion.
- Fungal saccharopepsin (EC:18.104.22.168) (proteinase A) (gene PEP4) is implicated in post-translational regulation of vacuolar hydrolases.
- Yeast barrierpepsin (EC:22.214.171.124) (gene BAR1); a protease that cleaves alpha-factor and thus acts as an antagonist of the mating pheromone.
- Fission yeast Sxa1 may be involved in degrading or processing the mating pheromones [PMID: 1549128].
- In plants, phytepsin (EC:126.96.36.199) degrades seed storage proteins and nepenthesin (EC 188.8.131.52) from a pitcher plant digests insect proteins.
- Plasmepsins (EC:184.108.40.206 and EC:220.127.116.11) from Plasmodium species are important for the degradation of host haemoglobin.
- Non-peptidase homologues where one or more active site residues have been replaced, include mammalian pregnancy-associated glycoproteins, an allergen from a cockroach, and a xylanase inhibitor [PMID: 15166216].