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Chymotrypsin (EC 3.4.21.1, chymotrypsins A and B, alpha-chymar ophth, avazyme, chymar, chymotest, enzeon, quimar, quimotrase, alpha-chymar, alpha-chymotrypsin A, alpha-chymotrypsin) is a digestive enzyme component of pancreatic juice acting in the duodenum, where it performs proteolysis, the breakdown of proteins and polypeptides. Chymotrypsin preferentially cleaves peptide amide bonds where the side chain of the amino acid N-terminal to the scissile amide bond (the P1 position) is a large hydrophobic amino acid (tyrosine, tryptophan, and phenylalanine). These amino acids contain an aromatic ring in their side chain that fits into a hydrophobic pocket (the S1 position) of the enzyme. It is activated in the presence of trypsin. The hydrophobic and shape complementarity between the peptide substrate P1 side chain and the enzyme S1 binding cavity accounts for the substrate specificity of this enzyme. Chymotrypsin also hydrolyzes other amide bonds in peptides at slower rates, particularly those containing leucine at the P1 position.
A protease is an enzyme that catalyzes proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the formation of new protein products. They do this by cleaving the peptide bonds within proteins by hydrolysis, a reaction where water breaks bonds. Proteases are involved in numerous biological pathways, including digestion of ingested proteins, protein catabolism, and cell signaling.
Chymosin or rennin is a protease found in rennet. It is an aspartic endopeptidase belonging to MEROPS A1 family. It is produced by newborn ruminant animals in the lining of the abomasum to curdle the milk they ingest, allowing a longer residence in the bowels and better absorption. It is widely used in the production of cheese.
A metalloproteinase, or metalloprotease, is any protease enzyme whose catalytic mechanism involves a metal. An example is ADAM12 which plays a significant role in the fusion of muscle cells during embryo development, in a process known as myogenesis.
Aspergillopepsin I is an enzyme. This enzyme catalyses the following chemical reaction
Aspartic proteases are a catalytic type of protease enzymes that use an activated water molecule bound to one or more aspartate residues for catalysis of their peptide substrates. In general, they have two highly conserved aspartates in the active site and are optimally active at acidic pH. Nearly all known aspartyl proteases are inhibited by pepstatin.
Kexin is a prohormone-processing protease, specifically a yeast serine peptidase, found in the budding yeast. It catalyzes the cleavage of -Lys-Arg- and -Arg-Arg- bonds to process yeast alpha-factor pheromone and killer toxin precursors. The human homolog is PCSK4. It is a family of subtilisin-like peptidases. Even though there are a few prokaryote kexin-like peptidases, all kexins are eukaryotes. The enzyme is encoded by the yeast gene KEX2, and usually referred to in the scientific community as Kex2p. It shares structural similarities with the bacterial protease subtilisin. The first mammalian homologue of this protein to be identified was furin. In the mammal, kexin-like peptidases function in creating and regulating many differing proproteins.
Rhizomucor miehei is a species of fungus. It is commercially used to produce enzymes which can be used to produce a microbial rennet to curd milk and produce cheese.
Nepenthesin is an aspartic protease of plant origin that has so far been identified in the pitcher secretions of Nepenthes and in the leaves of Drosera peltata. It is similar to pepsin, but differs in that it also cleaves on either side of Asp residues and at Lys┼Arg. While more pH and temperature stable than porcine pepsin A, it is considerably less stable in urea or guanidine hydrochloride. It is the only known protein with such a stability profile.
Glutamyl endopeptidase is an extracellular bacterial serine protease of the glutamyl endopeptidase I family that was initially isolated from the Staphylococcus aureus strain V8. The protease is, hence, commonly referred to as "V8 protease", or alternatively SspA from its corresponding gene.
Oryzin is an enzyme. This enzyme catalyses the following chemical reaction
Streptopain is an enzyme. This enzyme catalyses the following chemical reaction
Aspergilloglutamic peptidase, also called aspergillopepsin II is a proteolytic enzyme. The enzyme was previously thought be an aspartic protease, but it was later shown to be a glutamic protease with a catalytic Glu residue at the active site, and was therefore renamed aspergilloglutamic peptidase.
Penicillopepsin is an enzyme. This enzyme catalyses the following chemical reaction
Rhizopuspepsin is an enzyme. This enzyme catalyses the following chemical reaction
Endothiapepsin is an enzyme. This enzyme catalyses the following chemical reaction
Scytalidocarboxyl peptidase B, also known as Scytalidoglutamic peptidase and Scytalidopepsin B is a proteolytic enzyme. It was previously thought to be an aspartic protease, but determination of its molecular structure showed it to belong a novel group of proteases, glutamic protease.
Peptidyl-Asp metalloendopeptidase is an enzyme. This enzyme catalyses the following chemical reaction
Glutamic proteases are a group of proteolytic enzymes containing a glutamic acid residue within the active site. This type of protease was first described in 2004 and became the sixth catalytic type of protease. Members of this group of protease had been previously assumed to be an aspartate protease, but structural determination showed it to belong to a novel protease family. The first structure of this group of protease was scytalidoglutamic peptidase, the active site of which contains a catalytic dyad, glutamic acid (E) and glutamine (Q), which give rise to the name eqolisin. This group of proteases are found primarily in pathogenic fungi affecting plant and human.
The sedolisin 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.
References
- ↑ Arima K, Yu J, Iwasaki S (1970). "Milk-clotting enzyme from Mucor pusillus var. Lindt". Milk-clotting enzyme from Mucor pusillus var. lindt. Methods Enzymol. Vol. 19. pp. 446–459. doi:10.1016/0076-6879(70)19033-1. ISBN 978-0-12-181881-4.
- ↑ Ottesen M, Rickert W (1970). The acid protease of Mucor miehei. Methods Enzymol. Vol. 19. pp. 459–460. doi:10.1016/0076-6879(70)19034-3.
- ↑ Sternberg M (December 1972). "Bond specificity, active site and milk clotting mechanism of the Mucor miehei protease". Biochimica et Biophysica Acta (BBA) - Protein Structure. 285 (2): 383–92. doi:10.1016/0005-2795(72)90324-8. PMID 4573298.
- ↑ Oka T, Ishino K, Tsuzuki H, Morihara K, Arima K (1973). "On the specificity of a rennin-like enzyme from Mucor pusillus". Agric. Biol. Chem. 37 (5): 1177–1184. doi: 10.1271/bbb1961.37.1177 .
- ↑ Baudys M, Foundling S, Pavlík M, Blundell T, Kostka V (August 1988). "Protein chemical characterization of Mucor pusillus aspartic proteinase. Amino acid sequence homology with the other aspartic proteinases, disulfide bond arrangement and site of carbohydrate attachment". FEBS Letters. 235 (1–2): 271–4. Bibcode:1988FEBSL.235..271B. doi: 10.1016/0014-5793(88)81277-8 . PMID 3042459.
