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Encyclopedia > Peptidase

Peptidases (proteases [pronounced pro-tea-aces] and proteolytic enzymes are also commonly used) are enzymes which break peptide bonds of proteins. The process is called proteolytic cleavage. They use a molecule of water for this and are thus classified as hydrolases. Neuraminidase ribbon diagram An enzyme (in Greek en = in and zyme = leaven) is a protein, or protein complex, that catalyzes a chemical reaction and also controls the 3D orientation of the catalyzed substrates. ... Diagram showing the π-bonded amino acids and the point of rotation A peptide bond is a chemical bond formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule, releasing a molecule of water (H2O). ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... In science, a molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. ... Water (from the Old English word wæter) is a colorless, tasteless, and odorless substance that is essential to all known forms of life and is known also as the most universal solvent. ... In biochemistry, a hydrolase is an enzyme that can break a chemical bond by hydrolysis. ...

Contents


Classification

There are currently six classes of peptidases: 2004 is a leap year starting on Thursday of the Gregorian calendar. ...

The Threonine and Glutamic peptidases was not described until 1995 and 2004, respectively. The mechanism used to cleave a peptide bond involve making an amino acid residue (serine, cystein and threonine peptidases) or a water molecule (aspartic, metallo and glutamic peptidases) nucleophilic so that it can attack the peptide carbonyl group. One way to make a nucleophile is by a catalytic triad, where a histidine residue is used to activate serine, cysteine or threonine as a nucleophile. In biochemistry, a serine proteases or serine endopeptidases (newer name) are a class of peptidases which are characterised by the presence of a serine residue in the active center of the enzyme. ... The metalloendopeptidases (also called metalloproteinases or metalloproteases) are a class of enzymes from the group of endopeptidases. ... 1995 was a common year starting on Sunday of the Gregorian calendar. ... 2004 is a leap year starting on Thursday of the Gregorian calendar. ... In chemistry, a carbonyl group is a functional group composed of an atom of carbon double-bonded to an atom of oxygen. ... Histidine is one of the 20 most common natural amino acids, coded for in DNA. Nutritionally, in humans, histidine is considered an essential amino acid, but mostly only in children. ... Serine is one of the 20 most common natural amino acids on Earth. ... Cysteine is a naturally occurring hydrophobic amino acid which has a sulfhydryl group and is found in most proteins, however only in small quantities. ... Threonine is one of the 20 most common natural amino acids on Earth. ...


Occurrence

Peptidases occur naturally in all organisms and constitute 1-5% of the gene content. These enzymes are involved in a multitude of physiological reactions from simple digestion of food proteins to highly regulated cascades (e.g. the blood clotting cascade, the complement system and the invertbrate prophenoloxidase activating cascade). Peptidases can break either specific peptide bonds (limited proteolysis), depending on the amino acid sequence of a protein, or break down a complete peptide to amino acids (unlimited proteolysis). The activity can be a destructive change abolishing a proteins function or digesting it to its principal components, it can be an activation of a function or it can be a signal in a signalling pathway. The coagulation of blood is a complex process during which blood forms solid clots. ... The complement system is a complex biochemical cascade of the immune system, leading to cytolysis, chemotaxis, opsonization and inflammation, it can mark pathogens for phagocytosis. ... In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ...


Inhibitors

The function of peptidases is inhibited by protease inhibitor enzymes. Examples of protease inhibitors are the class of serpins (serine protease or peptidase inhibitors), incorporating alpha 1-antitrypsin. Other serpins are complement 1-inhibitor, antithrombin, alpha 1-antichymotrypsin, plasminogen activator inhibitor 1 (coagulation, fibrinolysis) and the recently discovered neuroserpin. For the drugs used in AIDS, please refer to protease inhibitor (pharmacology) In biology and biochemistry, protease inhibitors are molecules that inhibit the function of peptidases (old name: protease, hence the term protease inhibitor). ... Serine protease inhibitors or serpins (short for serine protease inhibitor) are a group of proteins that inhibit peptidases (old name: proteases). ... Alpha 1-antitrypsin or α1-antitrypsin (A1AT) is a serine protease inhibitor (serpin). ... The complement system is a complex biochemical cascade of the immune system, leading to cytolysis, chemotaxis, opsonization and inflammation, it can mark pathogens for phagocytosis. ... Antithrombin is a small molecule that inactivates several enzymes of the coagulation system. ... Plasminogen activator inhibitor-1 is the principal inhibitor of tissue plasminogen activator (tPA) and urokinase (uPA), the activators of plasminogen and hence fibrinolysis (the physiological breakdown of blood clots). ... The coagulation of blood is a complex process during which blood forms solid clots. ... Fibrinolysis is the process where a fibrin clot, the product of coagulation, is broken down. ...


The natural protease inhibitors are not to be confused with the protease inhibitors used in antiretroviral therapy. Some viruses, with HIV among them, depend on proteases in their reproductive cycle. Thus, protease inhibitors are developed as antiviral means. For the drugs used in AIDS, please refer to protease inhibitor (pharmacology) In biology and biochemistry, protease inhibitors are molecules that inhibit the function of peptidases (old name: protease, hence the term protease inhibitor). ... Protease inhibitors are a class of medication used to treat or prevent viral infections. ... A common alternate meaning of virus is computer virus. ... HIV (Human Immunodeficiency Virus) is a retrovirus that infects cells of the human immune system. ... Protease inhibitors are a class of medication used to treat or prevent viral infections. ...


Degradation

As peptidases are themselves peptides, one natually wonders if they degrade themselves. In fact, many peptidases are known to cleave themselves or each other. This may be an important method of regulation of peptidase activity.


Peptidase research

The field of peptidase research is enormous and Barrett and Rawlings estimated that approximately 8000 papers related to this field were published each year.


References

  • Barrett AJ, Rawlings ND, Woessner JF. The Handbook of Proteolytic Enzymes, 2nd ed. Academic Press, 2003. ISBN 0120796104.
  • Hedstrom L. Serine Protease Mechanism and Specificity. Chem Rev 2002;102:4501-4523.
  • Southan C. A genomic perspective on human proteases as drug targets. Drug Discov Today 2001;6:681-688.
  • Hooper NM. Proteases in Biology and Medicine. London: Portland Press, 2002. ISBN 1855781476.
  • Puente XS, Sanchez LM, Overall CM, Lopez-Otin C. Human and Mouse Proteases: a Comparative Genomic Approach. Nat Rev Genet 2003;4:544-558.
  • Ross J, Jiang H, Kanost MR, Wang Y. Serine proteases and their homologs in the Drosophila melanogaster genome: an initial analysis of sequence conservation and phylogenetic relationships. Gene 2003;304:117-31.
  • Puente XS, Lopez-Otin C. A Genomic Analysis of Rat Proteases and Protease Inhibitors. Genome Biol 2004;14:609-622.

External links

  • Merops - the peptidase database: http://merops.sanger.ac.uk/

  Results from FactBites:
 
Prolipoprotein signal peptidase in Escherichia coli is distinct from the M13 procoat protein signal peptidase -- ... (306 words)
Prolipoprotein signal peptidase in Escherichia coli is distinct from the M13 procoat protein signal peptidase -- Tokunaga et al.
Prolipoprotein signal peptidase in Escherichia coli is distinct from the M13 procoat protein signal peptidase
indicate that prolipoprotein signal peptidase is distinct from the M13
Protease - Wikipedia, the free encyclopedia (470 words)
Proteases (proteinases, peptidases or proteolytic enzymes) are enzymes which break peptide bonds between amino acids of proteins.
The threonine and glutamic peptidases was not described until 1995 and 2004, respectively.
Peptidases can break either specific peptide bonds (limited proteolysis), depending on the amino acid sequence of a protein, or break down a complete peptide to amino acids (unlimited proteolysis).
  More results at FactBites »

 
 

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