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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.1 Classification
There are currently six classes of peptidases:
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 threonineThreonine is one of the 20 most common natural amino acids on Earth. Nutritionally, in humans, threonine is also an essential amino acid. The threonine side chain can undergo O-linked glycosylation. Amino acids. as a nucleophile.
2 Occurrence
Peptidases occur naturally in all organisms and constitue 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 cascadeCoagulation is the thickening or congealing of any liquid into solid clots. This article is about a specific medical usage of the term with reference to human blood's mechanisms for forming scabs over wounds. The coagulation of human blood is a fairly com, the complement systemThe complement system is a complex biochemical cascade of the immune system, leading to cytolysis, chemotaxis, opsonization and inflammation, it can mark pathogens for phagocytosis. It consists of more than 35 proteins. 12 which are directly involved in t and the invertbrate prophenoloxidase activating cascade). Peptidases can break either specific peptide bonds (limited proteolysis), depending on the amino acidIn chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. In biochemistry, this shorter and more general term is frequently used to refer to alpha amino acids: those amino acids in which the amino and carb 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.
3 Inhibitors
The function of peptidases is inhibited by protease inhibitorFor 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 . Many naturally-occu enzymes. Examples of protease inhibitors are the class of serpins (serine protease or peptidase inhibitors), incorporating alpha 1-antitrypsinAlpha 1-antitrypsin or antitrypsin A1AT is a serine protease inhibitor (serpin). It protects tissue from enzymes from inflammatory cells, especially elastase. It is present in human blood at 1. 5 gram/ liter. Function A1AT is a 52 kDa serine protease inhi. Other serpins are complement 1-inhibitorThe complement system is a complex biochemical cascade of the immune system, leading to cytolysis, chemotaxis, opsonization and inflammation, it can mark pathogens for phagocytosis. It consists of more than 35 proteins. 12 which are directly involved in t, antithrombinAntithrombin is a small molecule that inactivates several enzymes of the coagulation system. Its affinity for these molecules (i. its effectivity) is enhanced by heparin. Function Antithrombin is a serpin (serine protease inhibitor) that inactivates a num, alpha 1-antichymotrypsin , plasminogen activator inhibitor 1 ( coagulation, fibrinolysis) and the recently discovered neuroserpin .
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.
