In eicosanoid biosynthesis, 5-lipoxygenase (5-LOX) converts arachidonic acid to which intermediate before producing leukotrienes?

• A Prostaglandin G2 (PGG2)
• B Thromboxane A2 (TXA2)
• C Prostacyclin I2 (PGI2)
• D 5-Hydroperoxyeicosatetraenoic acid (5-HPETE), then leukotriene A4 (LTA4) ✓

Explanation

5-LOX acts on free arachidonic acid in a two-step reaction: first generating 5-HPETE (5-hydroperoxyeicosatetraenoic acid), then dehydrating it to the unstable LTA4 (leukotriene A4, an epoxide). LTA4 is the branch point: LTA4 hydrolase converts it to LTB4 (a potent neutrophil chemotactic factor), while LTA4 conjugated to glutathione forms LTC4, which is further processed to LTD4 and LTE4 (the cysteinyl leukotrienes causing bronchoconstriction in asthma). COX-1/2 (cyclooxygenases) generate PGG2/PGH2 from arachidonic acid — the prostaglandin/thromboxane arm.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.