Isothiocyanate metabolism in generalist lepidopteran herbivores
Lepidopterans specialised on brassicaceous plants have been shown to possess biochemical adaptations preventing the formation of isothiocyanates. In faeces of generalist lepidopteran larvae glutathione (GSH) and cysteineglycine conjugates of plant-derived isothiocyanates were detected. The presence of GSH conjugates in larval faeces after consumption of crucifers suggests isothiocyanate-detoxification via GST (glutathione-S-transferase) activity in caterpillars. Active native GSTs were purified from midguts of Spodoptera littoralis larvae.It was shown that under conditions widely used for GST characterisation, S. littoralis-GSTs are capable of catalysing the conjugation reaction of GSH with isothiocyanates of different structures.