Reticuline isomerase AKR1B1 with aldo-keto reductase activity and detoxification function from the insect Blaps...

Herbivorous insects have evolved a dual adaptive strategy when exposed to small-molecule compounds such as alkaloids. They can utilize certain compounds to support growth and development, while detoxifying harmful ones through endogenous enzymes. Multiple enzymes, including aldo-keto reductases (AKRs) and cytochrome P450 enzymes, participate in these processes. Currently, the isomerase responsible for producing reticuline has only been identified in plants, with no reports of its existence in animals or insects to date. In light of this, from the transcriptome of Blaps rhynchopetera, we identified a novel aldo-keto reductase, AKR1B1, with diverse biological functions. This study demonstrates for the first time in vitro that AKR1B1 catalyzes the conversion of (S)-reticuline to (R)-reticuline, suggesting its dual role as both an aldo-keto reductase and an isomers enzyme. Virtual screening revealed tiaprofenic acid and pipemidic acid as small-molecule inhibitors of AKR1B1, effectively suppressing its catalytic activity toward (S)-reticuline. Antibody-based localization experiments demonstrated the highest expression levels of AKR1B1 in adults and midgut tissues, with minimal expression in eggs and muscle tissues. Furthermore, insecticide induction experiments confirmed AKR1B1's detoxification role in B. rhynchopetera. These findings establish AKR1B1 as a novel and critical player in insect compound metabolism and detoxification. This discovery provides new targets for developing insect-derived bifunctional enzymes for drug development and detoxification research, offering profound insights into the physiological mechanisms of insects.