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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 many biological functions, including digestion of ingested proteins, protein catabolism, and cell signaling.
Serine proteases 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. Serine proteases fall into two broad categories based on their structure: chymotrypsin-like (trypsin-like) or subtilisin-like.
Alpha 2-antiplasmin is a serine protease inhibitor (serpin) responsible for inactivating plasmin. Plasmin is an important enzyme that participates in fibrinolysis and degradation of various other proteins. This protein is encoded by the SERPINF2 gene.
Tryptase is the most abundant secretory granule-derived serine proteinase contained in mast cells and has been used as a marker for mast cell activation. Club cells contain tryptase, which is believed to be responsible for cleaving the hemagglutinin surface protein of influenza A virus, thereby activating it and causing the symptoms of flu.
Enteropeptidase is an enzyme produced by cells of the duodenum and is involved in digestion in humans and other animals. Enteropeptidase converts trypsinogen into its active form trypsin, resulting in the subsequent activation of pancreatic digestive enzymes. Absence of enteropeptidase results in intestinal digestion impairment.
A catalytic triad is a set of three coordinated amino acids that can be found in the active site of some enzymes. Catalytic triads are most commonly found in hydrolase and transferase enzymes. An acid-base-nucleophile triad is a common motif for generating a nucleophilic residue for covalent catalysis. The residues form a charge-relay network to polarise and activate the nucleophile, which attacks the substrate, forming a covalent intermediate which is then hydrolysed to release the product and regenerate free enzyme. The nucleophile is most commonly a serine or cysteine amino acid, but occasionally threonine or even selenocysteine. The 3D structure of the enzyme brings together the triad residues in a precise orientation, even though they may be far apart in the sequence.
An oxyanion hole is a pocket in the active site of an enzyme that stabilizes transition state negative charge on a deprotonated oxygen or alkoxide. The pocket typically consists of backbone amides or positively charged residues. Stabilising the transition state lowers the activation energy necessary for the reaction, and so promotes catalysis. For example, proteases such as chymotrypsin contain an oxyanion hole to stabilise the tetrahedral intermediate anion formed during proteolysis and protects substrate's negatively charged oxygen from water molecules. Additionally, it may allow for insertion or positioning of a substrate, which would suffer from steric hindrance if it could not occupy the hole. Enzymes that catalyse multi-step reactions can have multiple oxyanion holes that stabilise different transition states in the reaction.
Granzyme A is a tryptase and is one of the five granzymes encoded in the human genome. In humans, GzmA is encoded by the GZMA gene in proximity to the GZMK gene on chromosome 5. This enzyme is present in cytotoxic T lymphocyte (CTL) granules.
Microbial collagenase is an enzyme. This enzyme catalyses the following chemical reaction
Tissue kallikrein is an enzyme. This enzyme catalyses the following chemical reaction
Enzyme catalysis is the increase in the rate of a process by a biological molecule, an "enzyme". Most enzymes are proteins, and most such processes are chemical reactions. Within the enzyme, generally catalysis occurs at a localized site, called the active site.
TEV protease is a highly sequence-specific cysteine protease from Tobacco Etch Virus (TEV). It is a member of the PA clan of chymotrypsin-like proteases. Due to its high sequence specificity, TEV protease is frequently used for the controlled cleavage of fusion proteins in vitro and in vivo.
Pancreatic secretory trypsin inhibitor (PSTI) also known as serine protease inhibitor Kazal-type 1 (SPINK1) or tumor-associated trypsin inhibitor (TATI) is a protein that in humans is encoded by the SPINK1 gene.
Kallikrein-6 is a protein that in humans is encoded by the KLK6 gene. Kallikrein-6 is also referred to as neurosin, protease M, hK6, or zyme. It is a 223 amino acid sequence, derived from its 244 original form, which contains a 16 residue presignal and 5 residue activation peptide.
The Kazal domain is an evolutionary conserved protein domain usually indicative of serine protease inhibitors. However, kazal-like domains are also seen in the extracellular part of agrins, which are not known to be protease inhibitors.
Oryzin is an enzyme. This enzyme catalyses the following chemical reaction
Streptogrisin B is an enzyme. This enzyme catalyses the following chemical reaction
Limulus clotting factor overbar C is an enzyme. This enzyme catalyses the following chemical reaction
Atrolysin C is an enzyme. This enzyme catalyses the following chemical reaction
References
- ↑ Hurion N, Fromentin H, Keil B (February 1979). "Specificity of the collagenolytic enzyme from the fungus Entomophthora coronata: comparison with the bacterial collagenase from Achromobacter iophagus". Archives of Biochemistry and Biophysics. 192 (2): 438–45. doi:10.1016/0003-9861(79)90113-9. PMID 219780.
- ↑ Grant GA, Eisen AZ, Bradshaw RA (1981). "Collagenolytic protease from fiddler crab (Uca pugilator)". Methods Enzymol. 80: 722–734. doi:10.1016/s0076-6879(81)80055-9.
- ↑ Welgus HG, Grant GA, Jeffrey JJ, Eisen AZ (October 1982). "Substrate specificity of the collagenolytic serine protease from Uca pugilator: studies with collagenous substrates". Biochemistry. 21 (21): 5183–9. doi:10.1021/bi00264a012. PMID 6756469.
- ↑ Welgus HG, Grant GA (April 1983). "Degradation of collagen substrates by a trypsin-like serine protease from the fiddler crab Uca pugilator". Biochemistry. 22 (9): 2228–33. doi:10.1021/bi00278a026. PMID 6305411.
- ↑ Klimova OA, Borukhov SI, Solovyeva NI, Balaevskaya TO (February 1990). "The isolation and properties of collagenolytic proteases from crab hepatopancreas". Biochemical and Biophysical Research Communications. 166 (3): 1411–20. doi:10.1016/0006-291x(90)91024-m. PMID 2154979.
- ↑ Lu PJ, Liu HC, Tsai IH (September 1990). "The midgut trypsins of shrimp (Penaeus monodon). High efficiency toward native protein substrates including collagens". Biological Chemistry Hoppe-Seyler. 371 (9): 851–9. doi:10.1515/bchm3.1990.371.2.851. PMID 1963309.
