Functional characterization of a desaturase from the tobacco hornworm moth (Manduca sexta) with bifunctional Z11- and 10,12-desaturase activity

The pheromone blend produced by the tobacco hornworm moth (Manduca sexta) (L.) female is unusually complex and contains two conjugated dienals and trienals together with two monounsaturated alkenals. Here, we describe the identification and construction of two genes encoding MsexKPSE and MsexAPTQ desaturases from a cDNA library prepared from the total RNA of the M. sexta pheromone gland. The MsexKPSE desaturase shares a high degree of similarity with Δ9-desaturases from different moth species. The functional expression of MsexAPTQ desaturase in Saccharomyces cerevisiae followed by a detailed GC–MS analysis of fatty acid methyl esters (FAME) and their derivatized products and gas-phase Fourier transform infrared (FTIR) spectroscopy of the extracted FAME confirms that this enzyme is a bifunctional Z-Δ11-desaturase. MsexAPTQ desaturase catalyses the production of Z11-hexadecenoate (Z11–16) and Z10E12- and E10E12-hexadecadienoates (Z10E12–16) via 1,4-desaturation of the Z11–16 substrate. The stereochemistry of 1,4-desaturation and formation of isomers is discussed.