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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.
Protease-activated receptors(PAR) are a subfamily of related G protein-coupled receptors that are activated by cleavage of part of their extracellular domain. They are highly expressed in platelets, and also on endothelial cells, fibroblasts, immune cells, myocytes, neurons, and tissues that line the gastrointestinal tract.
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.
Pepsin A is an enzyme. This enzyme catalyses the following chemical reaction
Tissue kallikrein 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.
Actinidain is a type of cysteine protease enzyme found in fruits including kiwifruit, pineapple, mango, banana, figs, and papaya. This enzyme is part of the peptidase C1 family of papain-like proteases.
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.
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.
Thermitase is an enzyme. This enzyme catalyses the following chemical reaction
Streptogrisin B is an enzyme. This enzyme catalyses the following chemical reaction
Penicillopepsin 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.
Bacillolysin is an enzyme. This enzyme catalyses the following chemical reaction
A protein superfamily is the largest grouping (clade) of proteins for which common ancestry can be inferred. Usually this common ancestry is inferred from structural alignment and mechanistic similarity, even if no sequence similarity is evident. Sequence homology can then be deduced even if not apparent. Superfamilies typically contain several protein families which show sequence similarity within each family. The term protein clan is commonly used for protease and glycosyl hydrolases superfamilies based on the MEROPS and CAZy classification systems.
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.
Randy John Read is a Wellcome Trust Principal Research Fellow and professor of protein crystallography at the University of Cambridge.
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.
References
- ↑ Johnson P, Smillie LB (May 1971). "The disulfide bridge sequences of a serine protease of wide specificity from Streptomyces griseus". Canadian Journal of Biochemistry. 49 (5): 548–62. doi:10.1139/o71-082. PMID 5575653.
- ↑ Sielecki AR, Hendrickson WA, Broughton CG, Delbaere LT, Brayer GD, James MN (November 1979). "Protein structure refinement: Streptomyces griseus serine protease A at 1.8 A resolution". Journal of Molecular Biology. 134 (4): 781–804. doi:10.1016/0022-2836(79)90486-8. PMID 119870.
- ↑ James MN, Sielecki AR, Brayer GD, Delbaere LT, Bauer CA (November 1980). "Structures of product and inhibitor complexes of Streptomyces griseus protease A at 1.8 A resolution. A model for serine protease catalysis". Journal of Molecular Biology. 144 (1): 43–88. doi:10.1016/0022-2836(80)90214-4. PMID 6783761.
- ↑ Delbaere LT, Brayer GD (May 1985). "The 1.8 A structure of the complex between chymostatin and Streptomyces griseus protease A. A model for serine protease catalytic tetrahedral intermediates". Journal of Molecular Biology. 183 (1): 89–103. doi:10.1016/0022-2836(85)90283-9. PMID 3892018.
- ↑ Henderson G, Krygsman P, Liu CJ, Davey CC, Malek LT (August 1987). "Characterization and structure of genes for proteases A and B from Streptomyces griseus". Journal of Bacteriology. 169 (8): 3778–84. PMC 212465 . PMID 3112129.
