Well-known members of this family include sedolisin ("pseudomonalisin") found in Pseudomonas bacteria, xanthomonalisin ("sedolisin-B"), physarolisin as well as animal tripeptidyl peptidase I.

This group of enzymes contains a variation on the catalytic triad: unlike S8 which uses Ser-His-Asp, this group runs on Ser-Glu-Asp, with an additional acidic residue Asp in the oxyanion hole.

Most members of the family are produced as a precursor protein with N-terminal (InterPro: IPR015366) and sometimes C-terminal peptides that need to be cleaved off.

It shows preferential cleavage of Gly8-Ser in B chain of insulin most rapidly, followed by Leu11!Val, Cys(SO3H)19-Gly and Phe24-Phe.

Similar proteins (InterPro: IPR017001) are also found in archaea.