A Toxic Dipeptide from the Defense Glands of the Colorado Beetle

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Science  11 Jul 1986:
Vol. 233, Issue 4760, pp. 221-223
DOI: 10.1126/science.233.4760.221


The Colorado beetle is protected against predators by the secretions of defensive glands located on the pronotum and the elytra. The single major compound of the secretion was identified as γ-L-glutamyl-L-2-amino-3(Z),5-hexadienoic acid by spectroscopic and chemical methods. This compound, which contains a nonprotein β,γ- unsaturated amino acid, is toxic to ants (Myrmica rubra) at a concentration 10-2 molar, which is less than its estimated concentration in the secretion (1.8 x 10-1 molar).