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Cyclooxygenase-2 (COX-2), also known as prostaglandin-endoperoxide synthase 2 (HUGO PTGS2), is an enzyme that in humans is encoded by the PTGS2 gene. [5] In humans it is one of three cyclooxygenases .
COX is a common target for anti-inflammatory drugs. The most significant difference between the isoenzymes, which allows for selective inhibition, is the substitution of isoleucine at position 523 in COX-1 with valine in COX-2. The smaller Val 523 residue in COX-2 allows access to a hydrophobic side-pocket in the enzyme (which Ile 523 ...
The two enzymes were renamed COX-1, referring to the original enzyme and COX-2. [5] Building on those results, scientists started focusing on selective COX-2 inhibitors . Enormous effort was spent on the development of NSAIDs between the 1960s and 1980 so there were numerous pharmacophores to test when COX-2 was discovered.
The COX-2 enzyme was discovered in 1988 by Daniel Simmons, a Brigham Young University researcher. [30] The mouse COX-2 gene was cloned by UCLA scientist Harvey Herschman, a finding published in 1991. [31] The basic research leading to the discovery of COX-2 inhibitors has been the subject of at least two lawsuits.
Structure of COX-2 inactivated by Aspirin. In the active site of each of the two enzymes, Serine 516 has been acetylated. Also visible is the salicylic acid which has transferred the acetyl group, and the heme cofactor. There are at least two different cyclooxygenase isozymes: COX-1 (PTGS1) and COX-2 (PTGS2).
COX-2 is an enzyme facultatively expressed in inflammation, and it is inhibition of COX-2 that produces the desirable effects of NSAIDs. [125] When nonselective COX-1/COX-2 inhibitors (such as aspirin, ibuprofen, and naproxen) lower stomach prostaglandin levels, ulcers of the stomach or duodenum and internal bleeding can result. [126]
The conversion from arachidonic acid to prostaglandin H 2 is a two-step process. First, COX-1 catalyzes the addition of two free oxygens to form the 1,2-dioxane bridge and a peroxide functional group to form prostaglandin G 2 (PGG 2). [3] Second, COX-2 reduces the peroxide functional group to a secondary alcohol, forming prostaglandin H 2.
COX enzymes are responsible for catalyzing the conversion of arachidonic acid to prostaglandins, which are used as precursors for other substances, in particular thromboxane A2. [8] Thromboxane A2 is a potent platelet activator, inducing changes in platelets that ultimately promote aggregation and the formation of clots .