A novel means for dealing with L-canavanine, a toxic metabolite.

L-canavanine is a highly toxic L-arginine analog found in some leguminous seeds. Larvae of the bruchid beetle Caryedes brasiliensis, collected in Costa Rica, subsist solely on tissues of the mature seed of Dioclea megacarpa, which contains more than 8 percent L-canavanine by dry weight. The arginyl-tRNA synthetase of the bruchid beetle larvae discriminates between L-arginine and L-canavanine, and canavanyl proteins are not synthesized. In this way, bruchid beetle larvae avoid an adverse biochemical effect of L-canavanine.