Biosynthesis of Linoleic Acid in Insects

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This proposal describes studies designed to characterize a novel 12 desaturase in insects. Vertebrates cannot synthesize and thus require a dietary source of linoleic acid, 18:2(n-6), which is used both as a structural component of membranes and as a precursor for the eicosanoids. Until recently, all animals, including insects, were considered unable to synthesize linoleic acid. Studies in our laboratory demonstrated that a number of insect species possess a 12 desaturase and are thus able to produce linoleic acid. Extensive research, funded by the NSF, was performed to unambiguously demonstrate that insect tissue, and not associated microorganisms, contain the 12 desaturase. Studies are proposed herein to characterize the 12 desaturase from three representative insect species, a cockroach, a cricket and an aphid. Work will be done to elucidate the substrate requirements and specificity for the desaturase, to optimize activity, to determine the number and nature of the components in the desaturase, to examine the physiological regulation of activity, to determine the fate of the newly synthesized linoleate and to begin work on the solubilization and purification of the enzyme. Significant fundamental knowledge of comparative lipid metabolism will be obtained from this work. %%% One of the important dietary requirements in all vertebrates, including humans, is the essentials fatty acid, linoleic acid. This fatty acid is required as a component of cell membranes as well as functioning as a precursor for other physiologically important compounds such as certain hormones. Until recently, all animals were considered unable to synthesize this fatty acid due to the absence of a specific enzyme, the 12 desaturase. However, we have discovered that many, but not all, species of insects possess this enzyme. Therefore, manipulation of this enzyme, novel in insects, holds the potential for insect control. The work described in this proposal is designed to examine this enzyme in greater detail, to compare it across insect species and to the similiar enzyme found in plants. Significant fundamental knowledge of comparative lipid metabolism will be obtained from this work.