Lepidopteran species, fatty acid

In the melanogaster subgroup, the same enzyme Desatl seems to be involved in the first desaturation step of pheromone synthesis (Figure 4.7), even if the specificity concerning the desaturation is somewhat modified (for example, in D. erecta, stearic acid is used for the first desaturation, instead of palmitic acid as in other species). In other Drosophila species, other enzymes could be involved Desat2 in D. ananassae and another yet unknown desaturase in D. virilis. The position of the double bond on carbon 11 in the latter species could indicate either that the desaturase acts on C20 saturated fatty acid, or that it has another unknown specificity, resembling the unusual specificities of some lepidopteran desaturases. 

The fatty acid content of the ovipositor tips of a variety of Lepidopteran species were determined by acid methanolysis followed by gas-liquid chromatography (GLC) (4.). In each case, unusual fatty acids corresponding to pheromone components were identified. For example, the tufted apple bud moth, Platynota idaeusalis, uses (E)—11—tetradecenyl acetate and alcohol as pheromone components (5.) and also contains (E) -11—tetradecenoic acid in its ovipositor tip. In several species, the fatty acid content of the rest of the insect also was determined. In each instance, the unusual fatty acid components were found only in the ovipositor tip or in the pheromone-producing gland located in the tip. 

Fig. (5). Lepidopteran pheromone biosynthetic pathways utilize fatty acid synthesis, desatiindiun, specific chain-shortening enzymes, and/or functional modification of tlie carbony l carbon to produce species-apecific acetate ester, aldehyde, alcohol, or hydrocarbon pheromone blends. Unsaturated hydrocarbons can be further modified to epoxides (adapted from ref. [21]).

Lepidopteran pheromones have been intensively studied for three decades, largely because of the economic importance of lepidopteran pests, but also because many of these species are easy to rear, and because the biosynthesis of their pheromones was easy to relate to fatty acids. Females of very many species of Lepidoptera release volatile chemicals to attract males for mating. Most of these compounds have the following characteristics ... 

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