Cloning and functional expression of a cDNA encoding a pheromone gland-specific acyl-CoA Delta(11)-desaturase of the cabbage looper moth, Trichoplusia ni

Desaturation of coenzyme-A esters of saturated fatty acids is a common feat ure of sex pheromone biosynthetic pathways in the Lepidoptera. The enzymes that catalyze this step share several biochemical properties with the ubiqu itous acyl-CoA Delta(9)-desaturases of animals and fungi, suggesting a comm on ancestral origin. Unlike metabolic acyl-CoA Delta(9)-desaturases, pherom one desaturases have evolved unusual regio- and stereoselective activities that contribute to the remarkable diversity of chemical structures used as pheromones in this large taxonomic group. In this report, we describe the i solation of a cDNA encoding a pheromone gland desaturase from the cabbage l ooper moth, Trichoplusia ni, a species in which all unsaturated pheromone p roducts are produced via a Delta(11)Z-desaturation mechanism. The largest O RF of the approximate to 1,250-bp cDNA encodes a 349-aa apoprotein (PDesat- Tn Delta(11)Z) with a predicted molecular mass of 40,240 Da, Its hydrophobi city profile is similar overall to those of rat and yeast Delta(9)-desatura ses, suggesting conserved transmembrane topology. A 182-aa core domain deli mited by conserved histidine-rich motifs implicated in iron-binding and cat alysis has 72 and 58% similarity (including conservative substitutions) to acyl-CoA Delta(9)Z-desaturases of rat and yeast, respectively. Northern blo t analysis revealed an approximate to 1,250-nt PDesat-Tn Delta(11)Z mRNA th at is consistent with the spatial and temporal distribution of Delta(11)-de saturase enzyme activity. Genetic transformation of a desaturase-deficient strain of the yeast Saccharomyces cerevisiae with an expression plasmid enc oding PDesat-Tn Delta(11)Z resulted in complementation of the strain's fatt y acid auxotrophy and the production of Delta(11)Z-unsaturated fatty acids.