Endogenous and induced monooxygenase activity in gypsy moth larvae feeding on natural and artificial diets

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Abstract
NADPH oxidase activity was measured in third to sixth instar gypsy moth larvae fed oak or pine foliage. Activity levels ranged from 400 to 1,900 pmol NADPH oxidized/min/mg microsomal protein, but enzyme activity was not correlated with host plant ingested. Similarly, activity levels in larvae fed diets containing inducers, such as the terpenoid α‐pinene or pentamethylbenzene, ranged from 700 to 1,500 pmol NADPH oxidized/min/mg protein, levels that were comparable to those measured for larvae fed control diets. O‐demethylase activity in older instar gypsy moth larvae fed pine averaged 109 pmol p‐nitrophenol/min/mg protein, and activity levels in those fed diet containing α‐pinene ranged from 22 to 55 pmol/min/mg protein. Although statistically significant, these induced O‐demethylase levels are well below those observed for Heliothis zea larvae. Our findings indicate that monooxygenases play a minor, if any, role in the ability of later instar gypsy moth larvae to develop successfully on pine foliage.