Ecdysone 3-epimerase from the midgut of Manduca sexta (L.).


Ecdysone 3-epimerase was partially purified by ammonium sulfate fractionation from the 100,000 g supernate of Manduca sexta midguts. The enzyme converts ecdysone and 20-hydroxyecdysone to their respective 3-epimers, requires NADH or NADPH and O2 for this reaction, and has the following kinetic parameters: for ecdysone, Km = 17.0 +/- 1.4 microM, Vmax = 110.6 +/- 14.6 pmol min-1 mg-1; for 20-hydroxyecdysone, Km = 47.3 +/- 7.5 microM, Vmax = 131.0 +/- 3.5 pmol min-1 mg-1: for NADPH, Km = 85.4 +/- 10.6 microM; for NADH, Km = 51.3 +/- 1.3 microM. The reaction is irreversible and can be inhibited by various ecdysteroids.

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@article{Mayer1979Ecdysone3F, title={Ecdysone 3-epimerase from the midgut of Manduca sexta (L.).}, author={R T Mayer and J L Durrant and G M Holman and G F Weirich and J A Svoboda}, journal={Steroids}, year={1979}, volume={34 5}, pages={555-62} }