Biosynthesis of 3-hydroxy fatty acids, the pheromone components of female mallard ducks, by cell-free preparations from the uropygial gland.

Diesters of 3-hydroxy C8, C10, and C12 acids, the female mallard duck pheromones, were found as the major products of the uropygial glands only during the breeding season. The 3-hydroxy acids were identified by mass spectrometry of the trimethylsilyl ethers of the methyl esters and of the diols derived from LiAlH4 reduction of the hydroxy acids. A cell-free extract from the gland catalyzed conversion of dodecanoic acid to 3-hydroxydodecanoic acid which was identified by radio thin-layer and radio gas chromatographic analysis of the enzymic products as methyl-3-acetoxydodecanoate and as diacetate of the diol generated by LiAlH4 reduction of the enzymic product. The enzymic introduction of the hydroxyl group at C-3 was catalyzed mainly by a 50,000g pellet prepared from a 1000g supernatant obtained from the cell-free extract. This reaction required ATP, CoA, and O2, and the CoA ester of the acid was more efficiently converted than the free acid to the 3-hydroxy acid. KCN at 1 mM and 50% CO did not inhibit the reaction. 3H from 3H2O was incorporated into 3-hydroxydodecanoic acid during the enzymic synthesis of this acid from dodecanoic acid. Mass spectrometry of the 3-hydroxy acid generated by the particulate fraction in the presence of H2 18O showed that 18O was incorporated as expected from hydration of a delta 2 double bond. From the above results it is tentatively concluded that peroxisomal acyl-CoA oxidase converts the acyl-CoA to the 2-enoyl-CoA which is hydrated to generate the 3-hydroxy acid.