Biosynthesis of Tiglic, Ethacrylic, and 2-Methylbutyric Acids in a Carabid Beetle, Pterostichus (Hypherpes) californicus
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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 [2,3,4,4-2H4]isoleucine during our biosynthetic experiments.
KeywordsBiosynthesis Defensive allomones Tiglic acid 2-Methylbutyric acid Ethacrylic acid Isoleucine Carabid beetles Pterostichus (Hypherpes) californicus Carabidae
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