An Iron 13<i>S</i>-Lipoxygenase with an α-Linolenic Acid Specific Hydroperoxidase Activity from <i>Fusarium oxysporum</i>

<div><p>Jasmonates constitute a family of lipid-derived signaling molecules that are abundant in higher plants. The biosynthetic pathway leading to plant jasmonates is initiated by 13-lipoxygenase-catalyzed oxygenation of α-linolenic acid into its 13-hydroperoxide derivative. A number of plant pathogenic fungi (e.g. <i>Fusarium oxysporum</i>) are also capable of producing jasmonates, however, by a yet unknown biosynthetic pathway. In a search for lipoxygenase in <i>F. oxysporum</i>, a reverse genetic approach was used and one of two from the genome predicted lipoxygenases (FoxLOX) was cloned. The enzyme was heterologously expressed in <i>E. coli</i>, purified via affinity chromatography, and its reaction mechanism characterized. FoxLOX was found to be a non-heme iron lipoxygenase, which oxidizes C₁₈-polyunsaturated fatty acids to 13<i>S</i>-hydroperoxy derivatives by an antarafacial reaction mechanism where the bis-allylic hydrogen abstraction is the rate-limiting step. With α-linolenic acid as substrate FoxLOX was found to exhibit a multifunctional activity, because the hydroperoxy derivatives formed are further converted to dihydroxy-, keto-, and epoxy alcohol derivatives.</p></div