Cyclo-oxygenase 1 (COX-1)
Also known as: COX-1, prostaglandin-endoperoxide synthase 1, PTGS1
The 'housekeeping' form of cyclo-oxygenase, present all the time in platelets, the stomach lining and the kidney. It makes the thromboxane that lets platelets clump and the prostaglandins that protect the stomach and keep the kidneys perfused; aspirin and other NSAIDs block it.
- Kind
- enzyme
- Also called
- COX-1, prostaglandin-endoperoxide synthase 1, PTGS1
- Where it is found
- Platelets, the gastric and duodenal mucosa, the kidney and vascular endothelium; present in most tissues at a basal level.
What it does
Cyclo-oxygenases convert arachidonic acid released from cell membranes into the prostaglandins and thromboxane that act as short-range messengers. COX-1 is constitutive: it is always present and supplies the everyday prostaglandins that keep the stomach lining coated in mucus and bicarbonate, maintain blood flow through the kidney when the body is stressed, and, in platelets, make thromboxane A2, the signal that recruits other platelets to a clot. Low-dose aspirin acetylates COX-1 irreversibly; because platelets have no nucleus they cannot replace the enzyme, so a small daily dose suppresses thromboxane for the platelet's whole life. Non-selective NSAIDs such as ibuprofen block COX-1 reversibly, which explains their shared risks: stomach ulcers and bleeding, reduced kidney perfusion in the dehydrated, and a temporary antiplatelet effect that can interfere with aspirin's.
Role in the body
Platelet aggregation (thromboxane A2), gastric mucosal protection and renal blood flow (prostaglandins).