Journal of Chemical Ecology 2007-05-01

Biosynthesis of tiglic, ethacrylic, and 2-methylbutyric acids in a carabid beetle, Pterostichus (Hypherpes) californicus.

Athula B Attygalle, Xiaogang Wu, Kipling W Will

Index: J. Chem. Ecol. 33(5) , 963-70, (2007)

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Abstract

Tiglic, 2-methylbutyric, and ethacrylic acids are found in the pygidial gland defensive fluid of many carabid beetles. By injecting a deuterium-labeled precursor into the carabid beetle Pterostichus (Hypherpes) californicus, and analyzing the defensive fluid by gas chromatography/mass spectrometry, we were able to demonstrate that tiglic and ethacrylic acids are biosynthesized from isoleucine via 2-methylbutyric acid. Moreover, we observed that the injection of L-isoleucine induces an increased production of tiglic acid in P. californicus. A strong primary kinetic isotope effect was found to operate in the dehydrogenation step of 2-methylbutyric acid to tiglic and ethacrylic acids. Consequently, ethacrylic acid was found to preferentially accumulate the deuterium labeling from [2,3,4,4-(2)H(4)]isoleucine during our biosynthetic experiments.