An aminoacylase in the gut lumen of lepidopteran larvae hydrolyzes fatty acid amino acid conjugates, elicitors of plant defense

Fatty acid amino acid conjugates (FACs) have been identified in Lepidopteran larvae as elicitors of plant defense. Plant responses include the production of primary defense compounds and induction of secondary defense strategies including attraction of parasitoid wasps. These elicitors are present despite fitness costs, suggesting that they are important for the larvae’s survival. In order to exploit FAC-mediated plant defense responses, an understanding of FAC purpose and metabolism is crucial. To clarify their role, enzymes involved in this metabolism are being investigated. In this work a previously undiscovered FAC hydrolase was purified from Heliothis virescens frass by liquid chromatography and was identified as an Aminoacylase like protein (L-ACY-1) using Tandem MS/MS and Edman sequencing. Comparisons between L-ACY-1 transcript levels, protein levels, and enzyme activities between three Heliothine species (H. virescens, Helicoverpa zea, and Heliothis subflexa) indicates that the enzyme may be more important for some species than others. L-ACY-1 appears to play a vastly different role in insects than ACYs do in mammals and may be involved in maintaining glutamine supplies for gut tissue metabolism. Identification of L-ACY-1 as a FAC hydrolase clarifies a previously uncharacterized portion of FAC metabolism.