Empowerment of 15-Lipoxygenase Catalytic Competence in Selective Oxidation of Membrane ETE-PE to Ferroptotic Death Signals, HpETE-PE

<i>sn2</i>-15-Hydroperoxy-eicasotetraenoyl-phosphatidylethanolamines (<i>sn</i>2-15-HpETE-PE) generated by mammalian 15-lipoxygenase/phosphatidylethanolamine binding protein-1 (15-LO/PEBP1) complex is a death signal in a recently identified type of programmed cell demise, ferroptosis. How the enzymatic complex selects <i>sn2</i>-ETE-PE as the substrate among 1 of ∼100 total oxidizable membrane PUFA phospholipids is a central, yet unresolved question. To unearth the highly selective and specific mechanisms of catalytic competence, we used a combination of redox lipidomics, mutational and computational structural analysis to show they stem from (i) reactivity toward readily accessible hexagonally organized membrane <i>sn2</i>-ETE-PEs, (ii) relative preponderance of <i>sn2</i>-ETE-PE species vs other <i>sn2</i>-ETE-PLs, and (iii) allosteric modification of the enzyme in the complex with PEBP1. This emphasizes the role of enzymatic vs random stochastic free radical reactions in ferroptotic death signaling.