In human neutrophils, 5-lipoxygenase (ALOX5) can mediate the lipoxygenation of eicosapentaenoic acid (EPA) to 5-hydroxy-eicosapentaenoic acid (5-HEPE) (Cipollina et al. 2014, Powell et al. 1995). Neutrophils treated with an ALOX5 inhibitor completely suppressed the formation of 5-oxo-EPA and its hydroxy precursor 5-HEPE, demonstrating that ALOX5 mediates the first step in 5-oxo-EPA biosynthesis (Cipollina et al. 2014).