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. In humans it is one of three cyclooxygenases.
History
Cyclooxygenase (COX) is the central enzyme in the biosynthetic pathway to prostaglandins from arachidonic acid. This protein was isolated more than 40 years ago and cloned in 1988.
Gene and isozymes
There are two isozymes of COX encoded by distinct gene products: a constitutive COX-1 (this enzyme) and an inducible COX-2, which differ in their regulation of expression and tissue distribution. The expression of these two transcripts is differentially regulated by relevant cytokines and growth factors. This gene encodes COX-1, which regulates angiogenesis in endothelial cells. COX-1 is also involved in cell signaling and maintaining tissue homeostasis. A splice variant of COX-1 termed COX-3 was identified in the central nervous system of dogs, but does not result in a functional protein in humans. Two smaller COX-1-derived proteins (the partial COX-1 proteins PCOX-1A and PCOX-1B) have also been discovered, but their precise roles are yet to be described.
Function
Prostaglandin-endoperoxide synthase (PTGS), also known as cyclooxygenase (COX), is the key enzyme in prostaglandin biosynthesis. It converts free arachidonic acid, released from membrane phospholipids at the sn-2 ester binding site by the enzymatic activity of phospholipase A2, to prostaglandin (PG) H2. The reaction involves both cyclooxygenase (dioxygenase) and hydroperoxidase (peroxidase) activity. The cyclooxygenase activity incorporates two oxygen molecules into arachidonic acid or alternate polyunsaturated fatty acid substrates, such as linoleic acid and eicosapentaenoic acid. Metabolism of arachidonic acid forms a labile intermediate peroxide, PGG2, which is reduced to the corresponding alcohol, PGH2, by the enzyme's hydroperoxidase activity.
While metabolizing arachidonic acid primarily to PGG2, COX-1 also converts this fatty acid to small amounts of a racemic mixture of 15-Hydroxyicosatetraenoic acids (i.e., 15-HETEs) composed of ~22% 15(R)-HETE and ~78% 15(S)-HETE stereoisomers as well as a small amount of 11(R)-HETE. The two 15-HETE stereoisomers have intrinsic biological activities but, perhaps more importantly, can be further metabolized to a major class of anti-inflammatory agents, the lipoxins. In addition, PGG2 and PGH2 rearrange non-enzymatically to a mixture of 12-Hydroxyheptadecatrienoic acids viz.,1 2-(S)-hydroxy-5Z,8E,10E-heptadecatrienoic acid (i.e. 12-HHT) and 12-(S)-hydroxy-5Z,8Z,10E-heptadecatrienoic acid plus Malonyldialdehyde. and can be metabolized by CYP2S1 to 12-HHT (see 12-Hydroxyheptadecatrienoic acid). 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. COX-1 is normally present in a variety of areas of the body, including not only the stomach but any site of inflammation.
Clinical significance
COX-1 is inhibited by nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin. Thromboxane A2, the major product of COX-1 in platelets, induces platelet aggregation. The inhibition of COX-1 is sufficient to explain why low dose aspirin is effective at reducing cardiac events.
See also
- Arachidonic acid
- Cyclooxygenase
- Cyclooxygenase 2
- NSAID
- Discovery and development of COX-2 selective inhibitors
- COX-2 selective inhibitor
References
- ^ GRCh38: Ensembl release 89: ENSG00000095303 – Ensembl, May 2017
- ^ GRCm38: Ensembl release 89: ENSMUSG00000047250 – Ensembl, May 2017
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- "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
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Further reading
- Richards JA, Petrel TA, Brueggemeier RW (February 2002). "Signaling pathways regulating aromatase and cyclooxygenases in normal and malignant breast cells". The Journal of Steroid Biochemistry and Molecular Biology. 80 (2): 203–12. doi:10.1016/S0960-0760(01)00187-X. PMID 11897504. S2CID 12728545.
- Wu T, Wu H, Wang J, Wang J (2011). "Expression and cellular localization of cyclooxygenases and prostaglandin E synthases in the hemorrhagic brain". Journal of Neuroinflammation. 8: 22. doi:10.1186/1742-2094-8-22. PMC 3062590. PMID 21385433.
- Jain S, Khuri FR, Shin DM (2004). "Prevention of head and neck cancer: current status and future prospects". Current Problems in Cancer. 28 (5): 265–86. doi:10.1016/j.currproblcancer.2004.05.003. PMID 15375804.
- Bingham S, Beswick PJ, Blum DE, Gray NM, Chessell IP (October 2006). "The role of the cylooxygenase pathway in nociception and pain". Seminars in Cell & Developmental Biology. 17 (5): 544–54. doi:10.1016/j.semcdb.2006.09.001. PMID 17071117.
- Diaz A, Reginato AM, Jimenez SA (May 1992). "Alternative splicing of human prostaglandin G/H synthase mRNA and evidence of differential regulation of the resulting transcripts by transforming growth factor beta 1, interleukin 1 beta, and tumor necrosis factor alpha". The Journal of Biological Chemistry. 267 (15): 10816–22. doi:10.1016/S0021-9258(19)50092-8. PMID 1587858.
- Takahashi Y, Ueda N, Yoshimoto T, Yamamoto S, Yokoyama C, Miyata A, Tanabe T, Fuse I, Hattori A, Shibata A (January 1992). "Immunoaffinity purification and cDNA cloning of human platelet prostaglandin endoperoxide synthase (cyclooxygenase)". Biochemical and Biophysical Research Communications. 182 (2): 433–8. doi:10.1016/0006-291X(92)91750-K. PMID 1734857.
- Vane JR, Mitchell JA, Appleton I, Tomlinson A, Bishop-Bailey D, Croxtall J, Willoughby DA (March 1994). "Inducible isoforms of cyclooxygenase and nitric-oxide synthase in inflammation". Proceedings of the National Academy of Sciences of the United States of America. 91 (6): 2046–50. Bibcode:1994PNAS...91.2046V. doi:10.1073/pnas.91.6.2046. PMC 43306. PMID 7510883.
- Mollace V, Colasanti M, Rodino P, Lauro GM, Nistico G (August 1994). "HIV coating gp 120 glycoprotein-dependent prostaglandin E2 release by human cultured astrocytoma cells is regulated by nitric oxide formation". Biochemical and Biophysical Research Communications. 203 (1): 87–92. doi:10.1006/bbrc.1994.2152. PMID 7521167.
- Inoue H, Yokoyama C, Hara S, Tone Y, Tanabe T (October 1995). "Transcriptional regulation of human prostaglandin-endoperoxide synthase-2 gene by lipopolysaccharide and phorbol ester in vascular endothelial cells. Involvement of both nuclear factor for interleukin-6 expression site and cAMP response element". The Journal of Biological Chemistry. 270 (42): 24965–71. doi:10.1074/jbc.270.42.24965. PMID 7559624.
- Ren Y, Loose-Mitchell DS, Kulmacz RJ (February 1995). "Prostaglandin H synthase-1: evaluation of C-terminus function". Archives of Biochemistry and Biophysics. 316 (2): 751–7. doi:10.1006/abbi.1995.1100. PMID 7864630.
- Picot D, Loll PJ, Garavito RM (January 1994). "The X-ray crystal structure of the membrane protein prostaglandin H2 synthase-1". Nature. 367 (6460): 243–9. Bibcode:1994Natur.367..243P. doi:10.1038/367243a0. PMID 8121489. S2CID 4340064.
- Kosaka T, Miyata A, Ihara H, Hara S, Sugimoto T, Takeda O, Takahashi E, Tanabe T (May 1994). "Characterization of the human gene (PTGS2) encoding prostaglandin-endoperoxide synthase 2". European Journal of Biochemistry. 221 (3): 889–97. doi:10.1111/j.1432-1033.1994.tb18804.x. PMID 8181472.
- Otto JC, DeWitt DL, Smith WL (August 1993). "N-glycosylation of prostaglandin endoperoxide synthases-1 and -2 and their orientations in the endoplasmic reticulum". The Journal of Biological Chemistry. 268 (24): 18234–42. doi:10.1016/S0021-9258(17)46835-9. PMID 8349699.
- O'Neill GP, Ford-Hutchinson AW (September 1993). "Expression of mRNA for cyclooxygenase-1 and cyclooxygenase-2 in human tissues". FEBS Letters. 330 (2): 156–60. doi:10.1016/0014-5793(93)80263-T. PMID 8365485. S2CID 26397839.
- Corasaniti MT, Melino G, Navarra M, Garaci E, Finazzi-Agrò A, Nisticò G (September 1995). "Death of cultured human neuroblastoma cells induced by HIV-1 gp120 is prevented by NMDA receptor antagonists and inhibitors of nitric oxide and cyclooxygenase". Neurodegeneration. 4 (3): 315–21. doi:10.1016/1055-8330(95)90021-7. PMID 8581564.
- Ballif BA, Mincek NV, Barratt JT, Wilson ML, Simmons DL (May 1996). "Interaction of cyclooxygenases with an apoptosis- and autoimmunity-associated protein". Proceedings of the National Academy of Sciences of the United States of America. 93 (11): 5544–9. Bibcode:1996PNAS...93.5544B. doi:10.1073/pnas.93.11.5544. PMC 39283. PMID 8643612.
- Hla T (January 1996). "Molecular characterization of the 5.2 KB isoform of the human cyclooxygenase-1 transcript". Prostaglandins. 51 (1): 81–5. doi:10.1016/0090-6980(95)00158-1. PMID 8900446.
- Mahida YR, Beltinger J, Makh S, Göke M, Gray T, Podolsky DK, Hawkey CJ (December 1997). "Adult human colonic subepithelial myofibroblasts express extracellular matrix proteins and cyclooxygenase-1 and -2". The American Journal of Physiology. 273 (6 Pt 1): G1341-8. doi:10.1152/ajpgi.1997.273.6.G1341. PMID 9435560.
- Tsujii M, Kawano S, Tsuji S, Sawaoka H, Hori M, DuBois RN (May 1998). "Cyclooxygenase regulates angiogenesis induced by colon cancer cells". Cell. 93 (5): 705–16. doi:10.1016/S0092-8674(00)81433-6. PMID 9630216. S2CID 12704830.
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