Peroxidase arachidonic acid-dependent

In this bromoaspirin-inactivated structure, Ser , which lies along the wall of the tunnel, is bromoacetylated, and a molecule of salicylate is also bound in the tunnel. Deep in the tunnel, at the far end, lies Tyr, a catalytically important residue. Heme-dependent peroxidase activity is implicated in the formation of a proposed Tyr radical, which is required for cyclooxygenase activity. Aspirin and other NSAIDs block the synthesis of prostaglandins by filling and blocking the tunnel, preventing the migration of arachidonic acid to Tyr in the active site at the back of the tunnel. 

The transformation of free arachidonic acid (8) to 12-HPETE (24) and 15-HPETE (16) is catalyzed by 12-LOX and 15-LOX, respectively (Scheme 3.6). These products are reduced to the corresponding hydroxy compounds 12-HETE (25) and 15-HETE (26) by cellular peroxidases. Arachidonic acid (8) is also transformed by 8-LOX into 8-HPETE (27). The first step of the biosynthesis of Upoxin A (LXA, 29) and lipoxin B (LXB, 30) is the formation of 16 by a 15-LOX. Subsequently, 16 is converted to form an epoxy intermediate, that is, 5S,6S-epoxy-15S-hydioxy-ETE (28). Then, depending on the ceU type, specific hydrolases form... 

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