Category: biosynthesis
Phospholipase A2 (PLA2) liberates arachidonic acid from membrane phospholipids on inflammatory or hormonal cue. AA flows through two main enzymatic branches: cyclooxygenase (COX-1 constitutive + COX-2 inducible) → prostaglandin H2 → tissue-specific prostaglandins (PGE2 pain/fever, PGI2 vasodilator, TXA2 platelet aggregation) — NSAID + coxib target. Lipoxygenase (5-LOX) → leukotriene A4 → LTB4 (chemotaxis), LTC4/D4/E4 (cysteinyl leukotrienes — asthma + allergic rhinitis) — montelukast / zileuton target. Glucocorticoids inhibit PLA2 (via lipocortin/annexin-1 induction), blocking the entire cascade upstream.