The sedolisin (MEROPS S53) family of peptidases are a family of serine proteases structurally related to the subtilisin (S8) family. Well-known members of this family include sedolisin ("pseudomonalisin") found in Pseudomonas bacteria, xanthomonalisin ("sedolisin-B"), physarolisin as well as animal tripeptidyl peptidase I. It is also known as sedolysin or serine-carboxyl peptidase. 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.
Their optimal pH is around 3. Most members of the family are produced as a precursor protein with N-terminal () and sometimes C-terminal peptides that need to be cleaved off.
Sedolisin (, pseudomonapepsin, sedolysin) is a serine protease. It is secreted by Pseudomonas sp. 101. It performs hydrolysis of the B chain of insulin at -Glu<sup>13</sup>-Ala-, -Leu<sup>15</sup>-Tyr- and -Phe<sup>25</sup>-Tyr-, and angiotensin I at -Tyr<sup>4</sup>-Ile-. A good synthetic substrate is Lys-Pro-Ile-Glu-Phe-Phe(NO<sub>2</sub>)-Arg-Leu.
Xanthomonalisin () is found in Xanthomonas bacteria. It cleaves caesin and clots milk.
Physarolisin (, physaropepsin) is a milk-clotting enzyme. It shows preferential cleavage of Gly<sup>8</sup>-Ser in B chain of insulin most rapidly, followed by Leu<sup>11</sup>!Val, Cys(SO<sub>3</sub>H)<sup>19</sup>-Gly and Phe<sup>24</sup>-Phe.
It is special in that it is cold-adapted. It was discovered in the slime mold Physarum flavicomum. Similar proteins () are also found in archaea.