cyclo-oxygenase pathway
Last reviewed 01/2018
Once arachidonic acid has been liberated cyclo-oxygenase catalyzes a step common to most body cells:
- arachidonic acid is converted to the cyclic endoperoxidase, PGG2, via an intermediate radical
- PGG2 is then converted to PGH2
The next prostanoid produced from PGH2 is largely dependent on the enzymes produced by the individual cell. For example:
- platelets have the enzyme thromboxane synthetase which can produce thromboxane A2 - TXA2
- vascular endothelium has the enzyme prostacyclin synthetase for the production of prostaglandin I2 - PGI2
- many cells have enzymes capable of producing prostaglandins D2, E2 and F2alpha: PD2, PE2, PF2alpha
Generally, the prostanoids have a short half-life. Most are rapidly taken up and degraded by intracellular enzymes. PGI2 is degraded by the kidney, also the route by which most prostanoid metabolites are excreted.
cyclo-oxygenase 1 and cyclo-oxygenase 2
non-steroidal anti-inflammatory drugs
COX-1 Vs COX-2 inhibitors (relative risk of GI side effects)