Biosynthesis of scarab beetle pheromones

Area of Science:

• * Insect chemical ecology
• * Biochemistry of natural products
• * Organic chemistry and biosynthesis

Background:

• * Scarab beetles (Coleoptera: Scarabaeidae) use diverse pheromones for chemical communication.
• * Gamma-lactones with unsaturated hydrocarbon chains are common pheromone structures.
• * Examples include buibuilactone, (R)-japonilure, and (S)-japonilure.

Purpose of the Study:

• * To elucidate the biosynthetic pathway of gamma-lactone pheromones in scarab beetles.
• * To identify the starting materials and key enzymatic steps involved in pheromone synthesis.
• * To investigate the mechanism of the hydroxylation reaction in pheromone biosynthesis.

Main Methods:

• * Incorporation of deuterated fatty acid precursors (e.g., palmitic acid, stearic acid, oleic acid) into pheromones by female *Anomala cuprea*.
• * Analysis of incorporated deuterium atoms in synthesized pheromone molecules.
• * Use of perdeuterated palmitic acid to study the hydroxylation mechanism.

Main Results:

• * Deuterated saturated and unsaturated fatty acids were incorporated into pheromones, while specific unsaturated fatty acids were not.
• * The biosynthetic pathway involves desaturation, 8-hydroxylation, chain shortening, and cyclization of fatty acids.
• * Hydroxylation is a direct process mediated by a specific fatty acid hydroxylase, not involving preceding desaturation or epoxidation.
• * Stereospecificity is lost after the hydroxylation step.

Conclusions:

• * Fatty acids are the direct precursors for gamma-lactone pheromone biosynthesis in *Anomala cuprea*.
• * The study reveals a novel fatty acid hydroxylation mechanism in insect pheromone production.
• * Understanding this pathway provides insights into insect chemical communication and natural product biosynthesis.