The sedolisin (

MEROPS MEROPS is an online database for peptidases (also known as proteases, proteinases and proteolytic enzymes) and their inhibitors. The classification scheme for peptidases was published by Rawlings & Barrett in 1993, and that for protein inhibito ...

S53) family of peptidases are a family of

serine protease Serine proteases (or serine endopeptidases) are enzymes that cleave peptide bonds in proteins. Serine serves as the nucleophilic amino acid at the (enzyme's) active site. They are found ubiquitously in both eukaryotes and prokaryotes. Serin ...

s structurally related to the

subtilisin Subtilisin is a protease (a protein-digesting enzyme) initially obtained from ''Bacillus subtilis''. Subtilisins belong to subtilases, a group of serine proteases that – like all serine proteases – initiate the nucleophilic attack on the ...

(S8) family. Well-known members of this family include sedolisin ("pseudomonalisin") found in ''

Pseudomonas ''Pseudomonas'' is a genus of Gram-negative bacteria belonging to the family Pseudomonadaceae in the class Gammaproteobacteria. The 348 members of the genus demonstrate a great deal of metabolic diversity and consequently are able to colonize a ...

'' 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 A catalytic triad is a set of three coordinated amino acid residues that can be found in the active site of some enzymes. Catalytic triads are most commonly found in hydrolase and transferase enzymes (e.g. proteases, amidases, esterases, aminoac ...

: unlike S8 which uses Ser-His-Asp, this group runs on Ser-Glu-Asp, with an additional acidic residue Asp in the

oxyanion hole An oxyanion hole is a pocket in the active site of an enzyme that stabilizes transition state negative charge on a deprotonation, deprotonated oxygen or alkoxide. The pocket typically consists of backbone amides or positively charged residues. Sta ...

. 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.

Family members

Sedolisin

Sedolisin (, ''pseudomonapepsin'', ''sedolysin'') is a serine protease. It is secreted by ''

'' sp. 101. It performs

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...

of the B chain of

insulin Insulin (, from Latin ''insula'', 'island') is a peptide hormone produced by beta cells of the pancreatic islets encoded in humans by the insulin (''INS)'' gene. It is the main Anabolism, anabolic hormone of the body. It regulates the metabol ...

at -Glu¹³-Ala-, -Leu¹⁵-Tyr- and -Phe²⁵-Tyr-, and

angiotensin I Angiotensin is a peptide hormone that causes vasoconstriction and an increase in blood pressure. It is part of the renin–angiotensin system, which regulates blood pressure. Angiotensin also stimulates the release of aldosterone from the adren ...

at -Tyr⁴-Ile-. A good synthetic substrate is Lys-Pro-Ile-Glu-Phe-Phe(NO₂)-Arg-Leu.

Xanthomonalisin

Xanthomonalisin () is found in ''

Xanthomonas ''Xanthomonas'' (from greek: ''xanthos'' – "yellow"; ''monas'' – "entity") is a genus of bacteria, many of which cause plant pathology, plant diseases. There are at least 27 plant associated ''Xanthomonas spp.'', that all together infect at l ...

'' bacteria. It cleaves caesin and clots milk.

Physarolisin

Physarolisin (, ''physaropepsin'') is a milk-clotting enzyme. 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. It is special in that it is cold-adapted. It was discovered in the

slime mold Slime mold or slime mould is an informal name given to a polyphyletic assemblage of unrelated eukaryotic organisms in the Stramenopiles, Rhizaria, Discoba, Amoebozoa and Holomycota clades. Most are near-microscopic; those in the Myxogastria ...

'' Physarum flavicomum''. Similar proteins () are also found in archaea.

References

External links

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