Ecdysone 20-monooxygenase, a cytochrome P450 enzyme from spinach, Spinacia oleracea

A microsomal preparation isolated from first leaves of 25-day-old spinach catalysed the hydroxylation of ecdysone to produce the insect moulting hormone, 20-hydroxyecdysone. Hydroxylation was dependent on NADPH and molecular oxygen, and was inhibited by carbon monoxide. Carbon monoxide inhibition was partially reversible by white light. Polyclonal antibodies to the Jerusalem artichoke NADPH-cytochrome P450 reductase inhibited the hydroxylation reaction as well as the spinach microsomal NADPH cytochrome c reductase. These results taken together establish ecdysone hydroxylation as a cytochrome P450 dependent reaction in spinach, which is known to synthesize large amounts of phytoecdysteroids.