Cystatin (IPR027214)

Short name: Cystatin

Overlapping homologous superfamilies


Family relationships


This entry consists of a group of cysteine protease inhibitors. They can be classified as [PMID: 20800088]:

  • Type 1: intracellular cystatins, but may also appear in significant amounts in body fluids [PMID: 3488317]. They are single-chain polypeptides of about 100 residues, which have neither disulphide bonds nor carbohydrate side chains. Type 1 cystatin includes cystatin-A/B.
  • Type 2: extracellular secreted polypeptides synthesised with a 19-28 residue signal peptide. They are broadly distributed and found in most body fluids [PMID: 3488317]. Type 2 cyctatin includes cystatin-C/D/M/F/SA/SN/G.
  • Type 3: multidomain cystatins, including kininogens, known as kinin precursor proteins [PMID: 6441591]. There are three different kininogens in mammals: H- (high molecular mass, IPR002395) and L- (low molecular mass) kininogen which are found in a number of species, and T-kininogen that is found only in rat.
  • Unclassified cystatins: cystatin-like proteins.
This entry represents the type1, type2 and cystatin-like proteins.

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0004869 cysteine-type endopeptidase inhibitor activity

Cellular Component

No terms assigned in this category.

Contributing signatures

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