Which isoform is primarily involved in protecting the stomach lining and promoting platelet aggregation?

• A. COX-2
• B. LOX
• C. COX-1
• D. CYP450

Answer: (C)

COX-1 is the constitutive enzyme that continuously generates prostaglandins important for protecting the stomach lining and supporting normal platelet function. In the stomach, COX-1–derived prostaglandins (like PGE2) help maintain the protective mucus layer, stimulate bicarbonate secretion, and preserve mucosal blood flow. In platelets, COX-1 drives the production of thromboxane A2, a key signal for platelet aggregation and clot formation. The other pathways have different roles: COX-2 is inducible and mainly fuels inflammation and pain; LOX produces leukotrienes involved in inflammatory responses; CYP450 enzymes metabolize a wide range of drugs and endogenous compounds. Therefore, the isoform most directly responsible for gastric protection and promoting platelet aggregation is COX-1.