Bombykol is a pheromone released by the female silkworm moth to attract mates. It is also the sex pheromone in the wild silk moth (Bombyx mandarina).[1][2] Discovered by Adolf Butenandt in 1959, it was the first pheromone to be characterized chemically.[3]
Minute quantities of this pheromone can be used per acre of land to confuse male insects about the location of their female partners. It can thus serve as a lure in traps to remove insects effectively without spraying crops with large amounts of pesticides. Butenandt named the substance after the moth's Latin name Bombyx mori.[4]
In vivo it appears that bombykol is the natural ligand for a pheromone binding protein, BmorPBP, which escorts the pheromone to the pheromone receptor.[5]
Biosynthesis
Bombykol is known to be derived from acetyl-CoA via the C-16 fatty acyl palmitoyl-CoA.[6] Palmitoyl-CoA is converted to bombykol in steps that involve desaturation and reductive modification of the carbonyl carbon.[7] Compared to other Type I pheromones, bombykol biosynthesis does not need chain-shortening or any other kind of modification of the terminal hydroxyl group.
A desaturase enzyme encoded by the gene Bmpgdesat1 (Desat1), produces the monoene (11Z)-hexadecenoyl-CoA as well as the diene (10E,12Z)-10,12-hexadecadienoyl-CoA. This desaturase is the only enzyme necessary to catalyze these two consecutive desaturation steps.[8]
The bombykol acyl precursor (10E,12Z)-10,12-hexadecadienoate is primarily found as a triacylglycerol ester in the cytoplasmic lipid droplets of pheromone gland cells of the moth. And when the adult females emerge from their pupae, the neurohormone PBAN (pheromone biosynthesis-activating neuropeptide) start signaling events that help control the lipolysis of the stored triacylglycerols, releasing (10E,12Z)-10,12-hexadecadienoate for its final reductive modification.[9][10][11] The mechanism of the lipolytic release of (10E,12Z)-10,12-hexadecadienoate from triacylglycerols is not completely known but the candidate lipase-encoding genes have been identified.[9][10]
