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Encyclopedia > Protease

Proteases (proteinases, peptidases, or proteolytic enzymes) are enzymes that break peptide bonds between amino acids of proteins. The process is called peptide cleavage, a common mechanism of activation or inactivation of enzymes, especially those involved in blood coagulation or digestion. They use a molecule of water for this and are thus classified as hydrolases. Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... 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 chemistry, a molecule is an aggregate of two or more atoms in a definite arrangement held together by chemical bonds [1] [2] [3] [4] [5]. Chemical substances are not infinitely divisible into smaller fractions of the same substance: a molecule is generally considered the smallest particle of a pure... Impact of a drop of water. ... In biochemistry, a hydrolase is an enzyme that can break a chemical bond by hydrolysis. ...

Contents

Classification

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

The threonine and glutamic acid proteases were not described until 1995 and 2004, respectively. The mechanism used to cleave a peptide bond involves making an amino acid residue that has the character of a polarized peptide bond (serine, cysteine and threonine peptidases) or a water molecule (aspartic acid, metallo- and glutamic acid 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. Crystal structure of Trypsin, a typical serine protease. ... Proteases are enzymes that degrade polypeptides. ... Aspartic acid Aspartic acid proteases are protease enzymes which have an aspartic acid residue in the active site of the enzyme. ... Plasmepsins are a class of at least 10 enzymes produced by the plasmodium parasite. ... The metalloendopeptidases (also called metalloproteinases or metalloproteases) are a class of enzymes from the group of endopeptidases. ... 1995 (MCMXCV) was a common year starting on Sunday of the Gregorian calendar. ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... Carbonyl group In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom. ... Three amino acid residues found inside the active site of certain proteases. ... Histidine is one of the 20 most common natural amino acids present in proteins. ... Serine is one of the 20 natural amino acids. ... Cysteine is a naturally occurring amino acid which has a thiol group and is found in most proteins, though only in small quantities. ... Threonine is one of the 20 natural amino acids. ...


Occurrence

Proteases 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, apoptosis pathways, and the invertebrate 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 protein's 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. ... A complement protein attacking an invader. ... A cell undergoing apoptosis. ... Phenylalanine is one of the standard amino acids. ...


Proteases are also a type of exotoxin, which is a virulence factor in bacteria pathogenesis. Bacteria exotoxic proteases destroy extracellular structures.


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. In biology and biochemistry, protease inhibitors are molecules that inhibit the function of peptidases (old name: protease, hence the term protease inhibitor). ... Serpins (short for serine protease inhibitor) are a group of structurally related proteins, many of which inhibit peptidases (enzymes that degrade protein, old name: proteases). ... Alpha 1-antitrypsin or α1-antitrypsin (A1AT) is a serine protease inhibitor (serpin). ... A complement protein attacking an invader. ... Image:Antithrombin. ... Alpha 1-antichymotrypsin is a alpha globulin glycoprotein and serpin. ... 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. ...


Natural protease inhibitors include the family of lipocalin proteins, which play a role in cell regulation and differentiation. Lipophilic ligands, attached to lipocalin proteins, have been found to possess tumor protease inhibiting properties. 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. The lipocalin family of proteins is a functionally and structurally diverse group. ... This article or section does not cite its references or sources. ... 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. ... Human immunodeficiency virus or HIV is a retrovirus that causes Acquired Immunodeficiency Syndrome (AIDS), a condition in which the immune system begins to fail, leading to life-threatening opportunistic infections. ... Protease inhibitors are a class of medication used to treat or prevent viral infections. ... Antiviral drugs are a class of medication used specifically for treating viral infections. ...


Degradation

Proteases, being themselves proteins, are known to be cleaved by other protease molecules, sometimes of the same variety. This may be an important method of regulation of peptidase activity.


Protease research

The field of protease research is enormous. Barrett and Rawlings estimated that approximately 8000 papers related to this field are published each year. For a look at current activities and interests of protease researchers, see the International Proteolysis Society web page.


References

  • Barrett A.J., Rawlings ND, Woessner JF. The Handbook of Proteolytic Enzymes, 2nd ed. Academic Press, 2003. ISBN 0-12-079610-4.
  • 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 1-85578-147-6.
  • 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


  Results from FactBites:
 
Protease - Wikipedia, the free encyclopedia (485 words)
Proteases (proteinases, peptidases, or proteolytic enzymes) are enzymes that break peptide bonds between amino acids of proteins.
Examples of protease inhibitors are the class of serpins (serine protease or peptidase inhibitors), incorporating alpha 1-antitrypsin.
The natural protease inhibitors are not to be confused with the protease inhibitors used in antiretroviral therapy.
Protease inhibitor (pharmacology) - Wikipedia, the free encyclopedia (383 words)
Protease inhibitors (PIs) are a class of medication used to treat or prevent infection by viruses, including HIV and Hepatitis C.
PIs prevent viral replication by inhibiting the activity of protease, an enzyme used by the viruses to cleave nascent proteins for final assembly of new virons.
Protease inhibitors were the second class of antiretroviral drugs developed.
  More results at FactBites »

 
 

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