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Cyclooxygenases have two main isoforms that are called COX-1 and COX-2 (as well as a COX-3). COX-1 is responsible for the synthesis of prostaglandin and thromboxane in many types of cells, including the gastro-intestinal tract and blood platelets. COX-2 plays a major role in prostaglandin biosynthesis in inflammatory cells and in the central ...
Aspirin is ≈170-fold more potent in inhibiting COX-1 than COX-2. [40] Studies of meloxicam 7.5 mg per day for 23 days find a level of gastric injury similar to that of a placebo , and for meloxicam 15 mg per day a level of injury lower than that of other NSAIDs; however, in clinical practice meloxicam can still cause some ulcer complications.
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 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 ...
These alternate metabolites of COX-1 may contribute to its activities. COX-1 promotes the production of the natural mucus lining that protects the inner stomach and contributes to reduced acid secretion and reduced pepsin content. [18] [19] COX-1 is normally present in a variety of areas of the body, including not only the stomach but any site ...
5743 19225 Ensembl ENSG00000073756 ENSMUSG00000032487 UniProt P35354 Q05769 RefSeq (mRNA) NM_000963 NM_011198 RefSeq (protein) NP_000954 NP_035328 Location (UCSC) Chr 1: 186.67 – 186.68 Mb Chr 1: 149.98 – 149.98 Mb PubMed search Wikidata View/Edit Human View/Edit Mouse Cyclooxygenase-2 (COX-2), also known as prostaglandin-endoperoxide synthase 2 (HUGO PTGS2), is an enzyme that in humans is ...
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]
Blockade of COX-1 by aspirin apparently results in the upregulation of COX-2 as part of a gastric defense. [194] There is no clear evidence that simultaneous use of a COX-2 inhibitor with aspirin may increase the risk of gastrointestinal injury. [195]