Lipoxygenases (LOXs) are enzymes that catalyze arachidonic acid (AA), a polyunsaturated fatty acid to leukotrienes (LTs), lipid mediators of the inflammatory response. Over activation of the leukotriene biosynthesis pathway is exhibited in diseases such as asthma and atherosclerosis. The conversion of AA to LTs is a two step reaction that involves a peroxidation followed by a hydrogen abstraction. LOXs differ by where the oxygen is inserted along the pentadiene. While LOXs can be found in plants, fungi and animals, 5-lipoygenase, 15-lipoxygenase 1 and 2, and 12-lipoxygenase are the major LOXs found in humans.