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In biology and biochemistry, protease inhibitors, or antiproteases, are molecules that inhibit the function of proteases. Many naturally occurring protease inhibitors are proteins.
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.
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.
Proteinase 3, also known as PRTN3, is an enzyme that in humans is encoded by the PRTN3 gene.
Subtilisin is a protease initially obtained from Bacillus subtilis.
Cathepsin G is a protein that in humans is encoded by the CTSG gene. It is one of the three serine proteases of the chymotrypsin family that are stored in the azurophil granules, and also a member of the peptidase S1 protein family. Cathepsin G plays an important role in eliminating intracellular pathogens and breaking down tissues at inflammatory sites, as well as in anti-inflammatory response.
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.
In molecular biology, Proteinase K is a broad-spectrum serine protease. The enzyme was discovered in 1974 in extracts of the fungus Parengyodontium album. Proteinase K is able to digest hair (keratin), hence, the name "Proteinase K". The predominant site of cleavage is the peptide bond adjacent to the carboxyl group of aliphatic and aromatic amino acids with blocked alpha amino groups. It is commonly used for its broad specificity. This enzyme belongs to Peptidase family S8 (subtilisin). The molecular weight of Proteinase K is 28,900 daltons.
Keratinases are proteolytic enzymes that digest keratin.
Cerevisin is an enzyme. This enzyme catalyses the following chemical reaction
Lysyl endopeptidase is an enzyme. This enzyme catalyses the following chemical reaction
Endopeptidase La is an enzyme. This enzyme catalyses hydrolysis of proteins in the presence of ATP.
Oryzin is an enzyme. This enzyme catalyses the following chemical reaction
Streptogrisin A is an enzyme. This enzyme catalyses the following chemical reaction
Streptogrisin B is an enzyme. This enzyme catalyses the following chemical reaction
Aqualysin 1 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.
Bacillolysin is an enzyme. This enzyme catalyses the following chemical reaction
The PA clan is the largest group of proteases with common ancestry as identified by structural homology. Members have a chymotrypsin-like fold and similar proteolysis mechanisms but can have identity of <10%. The clan contains both cysteine and serine proteases. PA clan proteases can be found in plants, animals, fungi, eubacteria, archaea and viruses.
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
- ↑ Mizusawa K, Yoshida F (November 1972). "Thermophilic Streptomyces alkaline proteinase. I. Isolation, crystallization, and physicochemical properties". The Journal of Biological Chemistry. 247 (21): 6978–84. PMID 5082135.
- ↑ Borgia P, Campbell LL (December 1974). "Properties of two homologous alkaline proteases from Streptomyces rectus". Journal of Bacteriology. 120 (3): 1109–15. PMC 245889 . PMID 4373436.
- ↑ Kleine R (1982). "Properties of thermitase, a thermostable serine protease from Thermoactinomyces vulgaris". Acta Biologica et Medica Germanica. 41 (1): 89–102. PMID 7051706.
- ↑ Meloun B, Baudyš M, Kostka V, Hausdorf G, Frömmel C, Höhne WE (1985). "Complete primary structure of thermitase from Thermoactinomyces vulgaris and its structural features related to the subtilisin-type proteinases". FEBS Lett. 183 (2): 195–200. doi: 10.1016/0014-5793(85)80775-4 .
- ↑ Teplyakov AV, Kuranova IP, Harutyunyan EH, Vainshtein BK, Frömmel C, Höhne WE, Wilson KS (July 1990). "Crystal structure of thermitase at 1.4 A resolution". Journal of Molecular Biology. 214 (1): 261–79. doi: 10.1016/0022-2836(90)90160-n . PMID 2196375.
