Please note: this site relies heavily on the use of javascript. Without a javascript-enabled browser, this site will not function correctly. Please enable javascript and reload the page, or switch to a different browser.
2  structures 298  species 1  interaction 465  sequences 22  architectures

Family: Asp_protease (PF09668)

Summary: Aspartyl protease

Pfam includes annotations and additional family information from a range of different sources. These sources can be accessed via the tabs below.

This is the Wikipedia entry entitled "Aspartate protease". More...

Aspartate protease Edit Wikipedia article

Eukaryotic aspartyl protease
PDB 1lyb EBI.jpg
Structures of native and inhibited forms of human cathepsin D.[1]
Symbol Asp
Pfam PF00026
InterPro IPR001461
SCOP 1mpp
OPM superfamily 108
OPM protein 1lyb

Aspartic proteases are a catalytic type of protease enzymes that use an activated water molecule bound to one or more aspartate residues for catalysis of their peptide substrates. In general, they have two highly conserved aspartates in the active site and are optimally active at acidic pH. Nearly all known aspartyl proteases are inhibited by pepstatin.

Aspartic endopeptidases EC 3.4.23. of vertebrate, fungal and retroviral origin have been characterised.[2] More recently, aspartic endopeptidases associated with the processing of bacterial type 4 prepilin[3] and archaean preflagellin have been described.[4][5]

Eukaryotic aspartic proteases include pepsins, cathepsins, and renins. They have a two-domain structure, arising from ancestral duplication. Retroviral and retrotransposon proteases (Pfam PF00077) are much smaller and appear to be homologous to a single domain of the eukaryotic aspartyl proteases. Each domain contributes a catalytic Asp residue, with an extended active site cleft localized between the two lobes of the molecule. One lobe has probably evolved from the other through a gene duplication event in the distant past. In modern-day enzymes, although the three-dimensional structures are very similar, the amino acid sequences are more divergent, except for the catalytic site motif, which is very conserved. The presence and position of disulfide bridges are other conserved features of aspartic peptidases.

Catalytic Mechanism

Proposed mechanism of peptide cleavage by aspartyl proteases.[6]

Aspartyl proteases are a highly specific family of proteases - they tend to cleave dipeptide bonds that have hydrophobic residues as well as a beta-methylene group. Unlike serine or cysteine proteases these proteases do not form a covalent intermediate during cleavage. Proteolysis therefore occurs in a single step.

While a number of different mechanisms for aspartyl proteases have been proposed, the most widely accepted is a general acid-base mechanism involving coordination of a water molecule between the two highly conserved aspartate residues.[6][7] One aspartate activates the water by abstracting a proton, enabling the water to perform a nucleophilic attack on the carbonyl carbon of the substrate scissile bond, generating a tetrahedral oxyanion intermediate. Rearrangement of this intermediate leads to protonation of the scissile amide which results in the splitting of the substrate peptide into two product peptides.


Pepstatin is an inhibitor of aspartate proteases.


Five superfamilies (clans) of aspartic proteases are known, each representing an independent evolution of the same active site and mechanisms. Each superfamily contains several families with similar sequences. The MEROPS classification system names these clans alphabetically.


PDB 1htr EBI.jpg
crystal and molecular structures of human progastricsin at 1.62 angstroms resolution
Symbol A1_Propeptide
Pfam PF07966
InterPro IPR012848

Many eukaryotic aspartic endopeptidases (MEROPS peptidase family A1) are synthesised with signal and propeptides. The animal pepsin-like endopeptidase propeptides form a distinct family of propeptides, which contain a conserved motif approximately 30 residues long. In pepsinogen A, the first 11 residues of the mature pepsin sequence are displaced by residues of the propeptide. The propeptide contains two helices that block the active site cleft, in particular the conserved Asp11 residue, in pepsin, hydrogen bonds to a conserved Arg residue in the propeptide. This hydrogen bond stabilises the propeptide conformation and is probably responsible for triggering the conversion of pepsinogen to pepsin under acidic conditions.[8][9]



Human proteins containing this domain


Other organisms

External links

See also


  1. ^ Baldwin ET, Bhat TN, Gulnik S; et al. (July 1993). "Crystal structures of native and inhibited forms of human cathepsin D: implications for lysosomal targeting and drug design". Proc. Natl. Acad. Sci. U.S.A. 90 (14): 6796–800. doi:10.1073/pnas.90.14.6796. PMC 47019. PMID 8393577. 
  2. ^ Szecsi PB (1992). "The aspartic proteases". Scand. J. Clin. Lab. In vest. Suppl. 210: 5–22. doi:10.3109/00365519209104650. PMID 1455179. 
  3. ^ Taylor R K, LaPointe CF (2000). "The type 4 prepilin peptidases comprise a novel family of aspartic acid proteases". J. Biol. Chem. 275 (2): 1502–10. doi:10.1074/jbc.275.2.1502. PMID 10625704. 
  4. ^ Jarrell KF, Ng SY, Chaban B (2006). "Archaeal flagella, bacterial flagella and type IV pili: a comparison of genes and posttranslational modifications". J. Mol. Microbiol. Bio technol. 11 (3): 167–91. doi:10.1159/000094053. PMID 16983194. 
  5. ^ Jarrell KF, Bardy SL (2003). "Cleavage of preflagellins by an aspartic acid signal peptidase is essential for flagellation in the archaeon Methanococcus voltae". Mol. Microbiol. 50 (4): 1339–1347. doi:10.1046/j.1365-2958.2003.03758.x. PMID 14622420. 
  6. ^ a b Suguna K, Padlan EA, Smith CW, Carlson WD, Davies DR (1987). "Binding of a reduced peptide inhibitor to the aspartic proteinase from Rhizopus chinensis: implications for a mechanism of action". Proc. Natl. Acad. Sci. U.S.A. 84 (20): 7009–13. doi:10.1073/pnas.84.20.7009. PMC 299218. PMID 3313384. 
  7. ^ Brik A, Wong CH (2003). "HIV-1 protease: mechanism and drug discovery". Org. Biomol. Chem. 1 (1): 5–14. doi:10.1039/b208248a. PMID 12929379. 
  8. ^ Hartsuck JA, Koelsch G, Remington SJ (May 1992). "The high-resolution crystal structure of porcine pepsinogen". Proteins 13 (1): 1–25. doi:10.1002/prot.340130102. PMID 1594574. 
  9. ^ Sielecki AR, Fujinaga M, Read RJ, James MN (June 1991). "Refined structure of porcine pepsinogen at 1.8 A resolution". J. Mol. Biol. 219 (4): 671–92. doi:10.1016/0022-2836(91)90664-R. PMID 2056534. 

This article incorporates text from the public domain Pfam and InterPro IPR000036 This article incorporates text from the public domain Pfam and InterPro IPR012848

This page is based on a Wikipedia article. The text is available under the Creative Commons Attribution/Share-Alike License.

This tab holds the annotation information that is stored in the Pfam database. As we move to using Wikipedia as our main source of annotation, the contents of this tab will be gradually replaced by the Wikipedia tab.

Aspartyl protease Provide feedback

This family of eukaryotic aspartyl proteases have a fold similar to retroviral proteases which implies they function proteolytically during regulated protein turnover [1].

Literature references

  1. Sirkis R, Gerst JE, Fass D; , J Mol Biol. 2006;364:376-387.: Ddi1, a eukaryotic protein with the retroviral protease fold. PUBMED:17010377 EPMC:17010377

This tab holds annotation information from the InterPro database.

InterPro entry IPR019103

This domain is found in eukaryotic aspartyl protease DDI1. The remarkable structural similarity between this central domain of DDI1 and the retroviral proteases suggests that DDI1 functions proteolytically during regulated protein turnover [PUBMED:17010377].

Gene Ontology

The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.

Domain organisation

Below is a listing of the unique domain organisations or architectures in which this domain is found. More...

Loading domain graphics...

Pfam Clan

This family is a member of clan Peptidase_AA (CL0129), which has the following description:

This clan contains aspartic peptidases, including the pepsins and retropepsins. These enzymes contains a catalytic dyad composed of two aspartates. In the retropepsins one is provided by each copy of a homodimeric protein, whereas in the pepsin-like peptidases these aspartates come from a single protein composed of two duplicated domains.

The clan contains the following 14 members:

Asp Asp_protease Asp_protease_2 DUF1758 gag-asp_proteas Peptidase_A2B Peptidase_A2E Peptidase_A3 RVP RVP_2 Spuma_A9PTase TAXi_C TAXi_N Zn_protease


We store a range of different sequence alignments for families. As well as the seed alignment from which the family is built, we provide the full alignment, generated by searching the sequence database (reference proteomes) using the family HMM. We also generate alignments using four representative proteomes (RP) sets, the UniProtKB sequence database, the NCBI sequence database, and our metagenomics sequence database. More...

View options

We make a range of alignments for each Pfam-A family. You can see a description of each above. You can view these alignments in various ways but please note that some types of alignment are never generated while others may not be available for all families, most commonly because the alignments are too large to handle.

Representative proteomes UniProt
Jalview View  View  View  View  View  View  View  View  View 
HTML View  View               
PP/heatmap 1 View               

1Cannot generate PP/Heatmap alignments for seeds; no PP data available

Key: ✓ available, x not generated, not available.

Format an alignment

Representative proteomes UniProt

Download options

We make all of our alignments available in Stockholm format. You can download them here as raw, plain text files or as gzip-compressed files.

Representative proteomes UniProt
Raw Stockholm Download   Download   Download   Download   Download   Download   Download   Download   Download  
Gzipped Download   Download   Download   Download   Download   Download   Download   Download   Download  

You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.

HMM logo

HMM logos is one way of visualising profile HMMs. Logos provide a quick overview of the properties of an HMM in a graphical form. You can see a more detailed description of HMM logos and find out how you can interpret them here. More...


This page displays the phylogenetic tree for this family's seed alignment. We use FastTree to calculate neighbour join trees with a local bootstrap based on 100 resamples (shown next to the tree nodes). FastTree calculates approximately-maximum-likelihood phylogenetic trees from our seed alignment.

Note: You can also download the data file for the tree.

Curation and family details

This section shows the detailed information about the Pfam family. You can see the definitions of many of the terms in this section in the glossary and a fuller explanation of the scoring system that we use in the scores section of the help pages.

Curation View help on the curation process

Seed source: Pfam-B_9589 (release 20.0)
Previous IDs: none
Type: Family
Author: Mistry J, Wood V
Number in seed: 10
Number in full: 465
Average length of the domain: 118.60 aa
Average identity of full alignment: 45 %
Average coverage of the sequence by the domain: 29.73 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 11927849 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 20.6 20.6
Trusted cut-off 20.6 20.6
Noise cut-off 20.5 20.5
Model length: 124
Family (HMM) version: 7
Download: download the raw HMM for this family

Species distribution

Sunburst controls


Weight segments by...

Change the size of the sunburst


Colour assignments

Archea Archea Eukaryota Eukaryota
Bacteria Bacteria Other sequences Other sequences
Viruses Viruses Unclassified Unclassified
Viroids Viroids Unclassified sequence Unclassified sequence


Align selected sequences to HMM

Generate a FASTA-format file

Clear selection

This visualisation provides a simple graphical representation of the distribution of this family across species. You can find the original interactive tree in the adjacent tab. More...

Loading sunburst data...

Tree controls


The tree shows the occurrence of this domain across different species. More...


Please note: for large trees this can take some time. While the tree is loading, you can safely switch away from this tab but if you browse away from the family page entirely, the tree will not be loaded.


There is 1 interaction for this family. More...



For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the Asp_protease domain has been found. There are 2 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein seqence.

Loading structure mapping...