Monooxygenases are enzymes that incorporate one hydroxyl group into substrates in many metabolic pathways. In this reaction, the two atoms of dioxygen are reduced to one hydroxyl group and one H₂O molecule by the concomitant oxidation of NAD(P)H. One important subset of the monooxygenases, the Cytochrome P450 omega hydroxylases, is used by cells to metabolize arachidonic acid (i.e. eicosatetraenoic acid) to the cell signaling molecules, 20-Hydroxyeicosatetraenoic acid or to reduce or totally inactivate the activate signaling molecules for example by hydoxylating leukotriene B4 to 20-hydroxy-leukotriene B5, 5-hydroxyeicosatetraenoic acid to 5,20-dihydroxyeicosatetraenoic acid, 5-oxo-eicosatetraenoic acid to 5-oxo-20-hydroxyeicosatetraenoic acid, 12-hydroxyeicosatetraenoic acid to 12,20-dihydroxyeicosatetraenoic acid, and [epoxyeicosatrienoic acid]]s to 20-hydroxy-epoxyeicosatrienoic acids.