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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 ...
Cyclooxygenase 1 (COX-1), also known as prostaglandin-endoperoxide synthase 1 (HUGO PTGS1), is an enzyme that in humans is encoded by the PTGS1 gene. [ 5 ] [ 6 ] In humans it is one of three cyclooxygenases .
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. It is involved in the conversion of arachidonic acid to prostaglandin H 2, an important precursor of prostacyclin, which is expressed in inflammation.
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-1 is responsible for the baseline levels of prostaglandins. COX-2 produces prostaglandins through stimulation. However, while COX-1 and COX-2 are both located in the blood vessels, stomach and the kidneys, prostaglandin levels are increased by COX-2 in scenarios of inflammation and growth.
The existing nonsteroidal anti-inflammatory drugs differ in their relative specificities for COX-2 and COX-1; while aspirin and ibuprofen inhibit COX-2 and COX-1 enzymes, other NSAIDs appear to have partial COX-2 specificity, particularly meloxicam . [39] Aspirin is ≈170-fold more potent in inhibiting COX-1 than COX-2. [40]
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.
Cyclooxygenase-3 (COX-3) is an enzyme that is encoded by the PTGS1 (COX1) gene, but is not functional in humans.COX-3 is the third and most recently discovered cyclooxygenase (COX3050) isozyme, while the first two to be discovered were COX-1 and COX-2.