Degradation and detoxification of canavanine by a specialized seed predator.

Larvae of the bruchid beetle Caryedes brasiliensis feed exclusively on seeds of the Neotropical legume Dioclea megacarpa, which contains 13 percent L-canavanine by dry weight. L-Canavanine, a nonprotein amino acid analog of L-arginine, exhibits potent insecticidal properties. Most of the seed nitrogen is sequestered in canavanine, and bruchid beetle larvae do not simply excrete this toxic compound. Instead, these larvae possess extraordinarily high urease activity, which facilitates the conversion of canavanine to ammonia through urea. In this way, canavanine is effectively detoxified and a supply of nitrogen for fixation into organic linkage is ensured.