InterPro domain: IPR013201

This entry represents a peptidase inhibitor domain, which belongs to MEROPS peptidase inhibitor family I29. The domain is also found at the N terminus of a variety of peptidase precursors that belong to MEROPS peptidase subfamily C1A; these include cathepsin L, papain, and procaricain ( P10056 ) [ 1 ]. It forms an alpha-helical domain that runs through the substrate-binding site, preventing access. Removal of this region by proteolytic cleavage results in activation of the enzyme. This domain is also found, in one or more copies, in a variety of cysteine peptidase inhibitors such as salarin [ 2 ].

1. The prosequence of procaricain forms an alpha-helical domain that prevents access to the substrate-binding cleft. Structure 4, 1193-203
2. A new type of cysteine proteinase inhibitor--the salarin gene from Atlantic salmon (Salmo salar L.) and Arctic charr (Salvelinus alpinus). Biochimie 85, 677-81