Involved in the inactivation of ecdysteroid molting hormones by converting ecdysteroids into 3-dehydroecdysteroids. ecdysone + O2 = 3-dehydroecdysone + H2O2 Highly expressed in the late stage of the last instar larval stage and the pre-pupal stage (PubMed:15813704). Detected at 4h into the last larval instar; however, expression levels are low during the feeding stage (PubMed:15813704). Levels increase from 16 h, reach a peak at 48h, quickly decrease just before puparium formation, and rise again after pupariation (PubMed:15813704). Highly expressed in midgut in the third instar larvae (PubMed:15813704). Induced by RH-0345, which is an ecdysone agonist used as insecticide. Belongs to the GMC oxidoreductase family.