Evolution of the Biosynthetic Pathway for Cyanogenic Glucosides in Lepidoptera.

Cyanogenic glucosides are widespread defence compounds in plants, and they are also found in some arthropods, especially within Lepidoptera. The aliphatic linamarin and lotaustralin are the most common cyanogenic glucosides in Lepidoptera, and they are biosynthesised de novo, and/or sequestered from food plants. Their biosynthetic pathway was elucidated in the burnet moth, Zygaena filipendulae, and consists of three enzymes: two cytochrome P450 enzymes, CYP405A2 and CYP332A3, and a glucosyl transferase, UGT33A1.

Spatial separation of the cyanogenic β-glucosidase ZfBGD2 and cyanogenic glucosides in the haemolymph of larvae facilitates cyanide release.

Low molecular weight compounds are typically used by insects and plants for defence against predators. They are often stored as inactive β-glucosides and kept separate from activating β-glucosidases. When the two components are mixed, the β-glucosides are hydrolysed releasing toxic aglucones.