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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.
Pepsin is an endopeptidase that breaks down proteins into smaller peptides. It is produced in the gastric chief cells of the stomach lining and is one of the main digestive enzymes in the digestive systems of humans and many other animals, where it helps digest the proteins in food. Pepsin is an aspartic protease, using a catalytic aspartate in its active site.
Pro-opiomelanocortin (POMC) is a precursor polypeptide with 241 amino acid residues. POMC is synthesized in corticotrophs of the anterior pituitary from the 267-amino-acid-long polypeptide precursor pre-pro-opiomelanocortin (pre-POMC), by the removal of a 26-amino-acid-long signal peptide sequence during translation. POMC is part of the central melanocortin system.
The melanocyte-stimulating hormones, known collectively as MSH, also known as melanotropins or intermedins, are a family of peptide hormones and neuropeptides consisting of α-melanocyte-stimulating hormone (α-MSH), β-melanocyte-stimulating hormone (β-MSH), and γ-melanocyte-stimulating hormone (γ-MSH) that are produced by cells in the pars intermedia of the anterior lobe of the pituitary gland.
An exopeptidase is any peptidase that catalyzes the cleavage of the terminal peptide bond; the process releases a single amino acid, dipeptide or a tripeptide from the peptide chain. Depending on whether the amino acid is released from the amino or the carboxy terminal, an exopeptidase is further classified as an aminopeptidase or a carboxypeptidase, respectively. Thus, an aminopeptidase, an enzyme in the brush border of the small intestine, will cleave a single amino acid from the amino terminal, whereas carboxypeptidase, which is a digestive enzyme present in pancreatic juice, will cleave a single amino acid from the carboxylic end of the peptide.
Pepsin A is an enzyme. This enzyme catalyses the following chemical reaction
Proprotein convertases (PPCs) are a family of proteins that activate other proteins. Many proteins are inactive when they are first synthesized, because they contain chains of amino acids that block their activity. Proprotein convertases remove those chains and activate the protein. The prototypical proprotein convertase is furin. Proprotein convertases have medical significance, because they are involved in many important biological processes, such as cholesterol synthesis. Compounds called proprotein convertase inhibitors can block their action, and block the target proteins from becoming active. Many proprotein convertases, especially furin and PACE4, are involved in pathological processes such as viral infection, inflammation, hypercholesterolemia, and cancer, and have been postulated as therapeutic targets for some of these diseases.
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.
Met-enkephalin, also known as metenkefalin (INN), sometimes referred to as opioid growth factor (OGF), is a naturally occurring, endogenous opioid peptide that has opioid effects of a relatively short duration. It is one of the two forms of enkephalin, the other being leu-enkephalin. The enkephalins are considered to be the primary endogenous ligands of the δ-opioid receptor, due to their high potency and selectivity for the site over the other endogenous opioids.
Prolyl endopeptidase (PE) also known as prolyl oligopeptidase or post-proline cleaving enzyme is an enzyme that in humans is encoded by the PREP gene.
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.
Urodilatin (URO) is a hormone that causes natriuresis by increasing renal blood flow. It is secreted in response to increased mean arterial pressure and increased blood volume from the cells of the distal tubule and collecting duct. It is important in oliguric patients as it lowers serum creatinine and increases urine output.
The discovery of an orally inactive peptide from snake venom established the important role of angiotensin converting enzyme (ACE) inhibitors in regulating blood pressure. This led to the development of captopril, the first ACE inhibitor. When the adverse effects of captopril became apparent new derivates were designed. Then after the discovery of two active sites of ACE: N-domain and C-domain, the development of domain-specific ACE inhibitors began.
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.
Ecadotril is a neutral endopeptidase inhibitor ((NEP) EC 3.4.24.11) and determined by the presence of peptidase family M13 as a neutral endopeptidase inhibited by phosphoramidon. Ecadotril is the (S)-enantiomer of racecadotril. NEP-like enzymes include the endothelin-converting enzymes. The peptidase M13 family believed to activate or inactivate oligopeptide (pro)-hormones such as opioid peptides, neprilysin is another member of this group, in the case of the metallopeptidases and aspartic, the nucleophiles clan or family for example MA, is an activated water molecule. The peptidase domain for members of this family also contains a bacterial member and resembles that of thermolysin the predicted active site residues for members of this family and thermolysin occur in the motif HEXXH. Thermolysin complexed with the inhibitor (S)-thiorphan are isomeric thiol-containing inhibitors of endopeptidase EC 24-11 (also called "enkephalinase").
Leumorphin, also known as dynorphin B1–29, is a naturally occurring endogenous opioid peptide. Derived as a proteolytic cleavage product of residues 226-254 of prodynorphin, leumorphin is a nonacosapeptide and has the sequence Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Gln-Phe-Lys-Val-Val-Thr-Arg-Ser-Gln-Glu-Asp-Pro-Asn-Ala-Tyr-Ser-Gly-Glu-Leu-Phe-Asp-Ala. It can be further reduced to dynorphin B and dynorphin B-14 by pitrilysin metallopeptidase 1, an enzyme of the endopeptidase family. Leumorphin behaves as a potent and selective κ-opioid receptor agonist, similarly to other endogenous opioid peptide derivatives of prodynorphin.
Lysine carboxypeptidase is an enzyme. This enzyme catalyses the following chemical reaction:
Caricain is an enzyme. This enzyme catalyses the following chemical reaction: Hydrolysis of proteins with broad specificity for peptide bonds, similar to those of papain and chymopapain
Leishmanolysin is an enzyme. This enzyme catalyses the following chemical reaction
Magnolysin is an enzyme. This enzyme catalyses the following chemical reaction
References
- ↑ Carvalho KM, Joudiou C, Boussetta H, Leseney AM, Cohen P (January 1992). "A peptide-hormone-inactivating endopeptidase in Xenopus laevis skin secretion". Proceedings of the National Academy of Sciences of the United States of America. 89 (1): 84–8. Bibcode:1992PNAS...89...84C. doi: 10.1073/pnas.89.1.84 . PMC 48180 . PMID 1729723.
- ↑ Delporte C, Carvalho KM, Leseney AM, Winand J, Christophe J, Cohen P (January 1992). "A new metallo- endopeptidase from human neuroblastoma NB-OK-1 cells which inactivates atrial natriuretic peptide by selective cleavage at the Ser123-Phe124 bond". Biochemical and Biophysical Research Communications. 182 (1): 158–64. doi:10.1016/s0006-291x(05)80125-1. PMID 1531011. S2CID 34703070.
- ↑ Joudiou C, Carvalho KM, Camarao G, Boussetta H, Cohen P (June 1993). "Characterization of the thermolysin-like cleavage of biologically active peptides by Xenopus laevis peptide hormone inactivating enzyme". Biochemistry. 32 (23): 5959–66. doi:10.1021/bi00074a006. PMID 8507636.
