Molecular model of cyclooxygenase-1 enzyme (COX-1, grey) complexed with eicosapentaenoic acid (EPA, yellow spheres). EPA is a polyunsaturated omega-3 fatty acid, present in fish oil. COX-1 is the enzyme that catalyses the reaction that converts EPA into prostaglandins, lipids used in the body for tissue repair and mediating inflammation. COX-1 also has a protoporphyrin IX ring (grey spheres) with cobalt (blue) in the centre.