| Type: | Active_site | Name: | Cysteine peptidase, cysteine active site |
| Description: | Thiol (cysteine) proteases (EC 3.4.22.-) [] are a family of proteolytic enzymes which contain an active site cysteine. Catalysis proceeds through a thioester intermediate and is facilitated by a nearby histidine side chain; an asparagine completes the essential catalytic triad.Cysteine peptidases have characteristic molecular topologies, which can be seen not only in their three-dimensional structures, but commonly also in the two-dimensional structures. These are peptidases in which the nucleophile is the sulphydryl group of a cysteine residue. Cysteine proteases are divided into clans (proteins which are evolutionary related), and further sub-divided into families, on the basis of the architecture of their catalytic dyad (cysteine-histidene) or triad [].Modification of the catalytic triad, especially of its first amino acid (cysteine), has been postulated as a suitable target for a chemical modulation of enzyme function. This is the case for silicateins, where the cysteine residue has been replaced by a serine []. Silicateins represent a group of enzymes possessing bi-functional activity; in addition to the silica-condensing activity, they possess a proteolytic (cathepsin-like) activity [].The sequences around the three active site residues are well conserved. This entry represents the cysteine active site. The catalytic triad consists of this entry, and . This catalytic triad detects mainly proteases of the C1 family, including papain and several cathepsins. | Short Name: | Pept_cys_AS |
| DB identifier | Type | Name |
|---|---|---|
| IPR013128 | Family | Peptidase C1A |
| IPR001300 | Domain | Peptidase C2, calpain, catalytic domain |
| IPR022684 | Family | Peptidase C2, calpain family |
| IPR015643 | Family | Peptidase C1A, cathepsin B |
| IPR015644 | Family | Peptidase C1A, cathepsin K |
| IPR015645 | Family | Peptidase C1A, placentally-expressed cathepsin |
