Ecdysone Oxidase, an enzyme from the blowfly Calliphora erythrocephala (Meigen)

In the blowfly, the formation of 3-dehydroecdysone from the insect molting hormone ecdysone is catalyzed by an enzyme which carries hydrogen from ecdysone and ecdysterone to oxygen. The enzyme is therefore called "ecdysone oxidase". Two methods are described for the detection of ecdysone oxidase activity, one using a radiolabelled substrate which is separated from the product by thin-layer chromatography after the reaction, and the other using dichloroindophenol, which is discoloured by the redox reaction. The ecdysone oxidase is purified by a factor of 2200 from prepupae of Calliphora erythrocephala using salt precipitation and ion exchange chromatography. The ecdysone oxidase has a Km value for ecdysone of 42muM. The pH optimum is 6.5. The temperature optimum lies at 45 degrees C. The ecdysone oxidase has a molecular weight of 240000.