Molecular Biology and Biochemistry of Lipoxygenases and Related Pathways

Abstract

Lipoxygenases (LOXs), a family of dioxygenases, with distinct regio-specificities have been found in both plants and mammals. The substrates for LOXs are linoleic and oc-linolenic acids from plants and arachidonic acid from mammals. The LOX pathway in animals produces bioactive lipids called eicosanoids to serve as autacoids, while plants also have unique LOX pathways to form signaling molecules termed octadecanoids. The studies with gene cloning have revealed the existence of several types of isoforms that exhibit a similar reaction with distinct expression or reaction properties, postulating specific roles of individual enzymes. As one of our studies, results are presented about the cloning, expression, and characterization of cDNA encoding an LOX isoform from potato tubers. We also provide the facets of the metabolic pathways of fatty acid hydroperoxide in potato tissues. Alternatively, we provide the approaches to identify the amino acid residues to determine the positional specificity of mouse 8-LOX that is a novel LOX inducible by phorbol diesters and its newly found human homologue, 15-LOX-2. Recently, some of LOX products have been shown to cause nuclear action as a ligand through binding to nuclear receptors. This presentation also reviews the biological significance of certain LOXs in relation to the onset of life-style diseases such as obesity.