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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.
Proteolysis is the breakdown of proteins into smaller polypeptides or amino acids. Uncatalysed, the hydrolysis of peptide bonds is extremely slow, taking hundreds of years. Proteolysis is typically catalysed by cellular enzymes called proteases, but may also occur by intra-molecular digestion.
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.
In biology and biochemistry, protease inhibitors, or antiproteases, are molecules that inhibit the function of proteases. Many naturally occurring protease inhibitors are proteins.
In molecular biology, elastase is an enzyme from the class of proteases (peptidases) that break down proteins. In particular, it is a serine protease.
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.
DD-transpeptidase is a bacterial enzyme that catalyzes the transfer of the R-L-αα-D-alanyl moiety of R-L-αα-D-alanyl-D-alanine carbonyl donors to the γ-OH of their active-site serine and from this to a final acceptor. It is involved in bacterial cell wall biosynthesis, namely, the transpeptidation that crosslinks the peptide side chains of peptidoglycan strands.
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.
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.
IgA protease is an enzyme. This enzyme catalyses the following chemical reaction[reaction equation needed]
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.
Brachyurin is an enzyme. This enzyme catalyses the Hydrolysis of proteins, with broad specificity for peptide bonds. Native collagen is cleaved about 75% of the length of the molecule from the N-terminus.
Lysyl endopeptidase is an enzyme. This enzyme catalyses the following chemical reaction
Oryzin is an enzyme. This enzyme catalyses the following chemical reaction
Pestivirus NS3 polyprotein peptidase is an enzyme. This enzyme catalyses the following chemical reaction
Ulp1 peptidase is an enzyme. This enzyme catalyses the following chemical reaction
The 3C-like protease (3CLpro) or main protease (Mpro), formally known as C30 endopeptidase or 3-chymotrypsin-like protease, is the main protease found in coronaviruses. It cleaves the coronavirus polyprotein at eleven conserved sites. It is a cysteine protease and a member of the PA clan of proteases. It has a cysteine-histidine catalytic dyad at its active site and cleaves a Gln–(Ser/Ala/Gly) peptide bond.
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.
Beta-lytic metalloendopeptidase is an enzyme. This enzyme catalyses the following chemical reaction
References
- ↑ Olson MO, Nagabhushan N, Dzwiniel M, Smillie LB, Whitaker DR (October 1970). "Primary structure of alpha-lytic protease: a bacterial homologue of the pancreatic serine proteases". Nature. 228 (5270): 438–42. doi:10.1038/228438a0. PMID 5482494.
- ↑ Polgar L (1987). "Structure and function of serine proteases". In Neuberger A, Brocklehurst K (eds.). New Comprehensive Biochemistry: Hydrolytic Enzymes. Vol. 16. Amsterdam: Elsevier. pp. 159–200.
- ↑ Epstein DM, Wensink PC (November 1988). "The alpha-lytic protease gene of Lysobacter enzymogenes. The nucleotide sequence predicts a large prepro-peptide with homology to pro-peptides of other chymotrypsin-like enzymes". The Journal of Biological Chemistry. 263 (32): 16586–90. PMID 3053694.
- ↑ Bone R, Frank D, Kettner CA, Agard DA (September 1989). "Structural analysis of specificity: alpha-lytic protease complexes with analogues of reaction intermediates". Biochemistry. 28 (19): 7600–9. doi:10.1021/bi00445a015. PMID 2611204.
- ↑ Meyer JG, Kim S, Maltby DA, Ghassemian M, Bandeira N, Komives EA (March 2014). "Expanding proteome coverage with orthogonal-specificity α-lytic proteases". Molecular & Cellular Proteomics. 13 (3): 823–35. doi:10.1074/mcp.M113.034710. PMC 3945911 . PMID 24425750.
- ↑ Lumpkin RJ, Gu H, Zhu Y, Leonard M, Ahmad AS, Clauser KR, Meyer JG, Bennett EJ, Komives EA (October 2017). "Site-specific identification and quantitation of endogenous SUMO modifications under native conditions". Nature Communications. 8 (1): 1171. doi:10.1038/s41467-017-01271-3. PMC 5660086 . PMID 29079793.
