Ecdysone 20-Hydroxylase in Midgut Mitochondriaof Manduca sexta(L.)
- 1 January 1978
- journal article
- research article
- Published by Walter de Gruyter GmbH in Hoppe-Seyler´s Zeitschrift Für Physiologische Chemie
- Vol. 359 (2), 1247-1258
- https://doi.org/10.1515/bchm2.1978.359.2.1247
Abstract
The conversion of .alpha.-ecdysone to 20-hydroxyecdysone in the midgut of M. sexta (L.) was catalyzed by a mitochondrial, cytochrome P450-mediated monooxygenase. The reaction required O2 and was inhibited by the presence of CO. Tricarboxylic acid cycle intermediates, such as succinate, malate and isocitrate, supported the hydroxylation as did NADPH, NADH, ATP and ADP. Temperature and pH optima were 30.degree. C and 8.5, respectively. The apparent Km and V values for the ecdysone 20-hydroxylase were 18.3 .+-. 6.8 .mu.M and 46.6 .+-. 14.2 pmol/min per mg protein. The midgut mitochondria contained malate dehydrogenase and .**GRAPHIC**. transhydrogenase. The presence of these enzymes suggested that the tricarboxylic acid cycle intermediates and NADH support the ecdysone hydroxylation indirectly by providing NADPH for the cytochrome P450 system. The content of cytochromes a + a3, b, c + c1, and P450 in midgut mitochondria was determined.This publication has 17 references indexed in Scilit:
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