Possible role for covalent modification in the reversible activation of ecdysone 20‐monooxygenase activity

Abstract

Evidence is presented for the reversible activation-inactivation of the microsoma1 ecdysone 20-monooxygenase from fat body of the cotton leafworm, Spodoptera littoralis, in a manner commensurate with reversible changes in its phosphorylation state. The activity of the monooxygenase was higher following preincubation with fluoride (an inhibitor of phosphoprotein phosphatases) than in its absence. Preincubation with alkaline phosphatase o r with CAMP-dependent protein kinase resulted in appreciable diminution or enhancement, respectively, in monooxygenase activity. Activation of ecdysone 20-monooxygenase activity could also be effected by incubation with a cytosolic fraction in the presence of CAMP, ATP, and fluoride; this activation was prevented by a CAMP-dependent protein kinase inhibitor. Similarly, inactivation of the monooxygenase was achieved by preincubation with cytosol, the effect being enhanced by Ca2+-calmodulin or by M g f ions. The combined results provide indirect evidence that the microsomal ecdysone 20-monooxygenase exists in an active phosphorylated form and an inactive dephosphorylated form, interconvertible by a CAMP-dependent protein kinase and a phosphoprotein phosphatase.

Studies on the black box: Incorporation of 3-oxo-7-dehydrocholesterol into ecdysteroids by Drosophila melanogaster and Manduca sexta

“…Unlike the other Halloween genes (Gilbert and Warren, 2005), Spook phosphorylation, like ecdysteroidogenesis, has been shown to be under control of the neuropeptide PTTH (Rewitz et al, 2009). As such, it may be analogous to the increase in activity observed when the 20-monooxygenase was subjected to in vitro phosphorylation (Hoggard et al, 1989). Furthermore, all of the other possible stable oxidation products of 3-oxo-7dC, i.e.…”

Discrete pulses of molting hormone, 20‐hydroxyecdysone, during late larval development of Drosophila melanogaster: Correlations with changes in gene activity

“…In turn, endogenous or exogenous 20E can up-regulate 26-hydroxylase activity Williams et al, 1997;Kayser et al, 1997). In addition to direct changes in P450 expression levels, the intrinsic activity of both of these enzymes may be directly modulated by reversible phosphorylation (Hoggard et al, 1989;Williams et al, 2000).…”

Induction of Enzymes Involved in Molting Hormone (Ecdysteroid) Inactivation by Ecdysteroids and an Agonist, 1,2-Dibenzoyl-1-tert-butylhydrazine (RH-5849)

“…We cannot discount the possibility that at least some of the observed induction events we now report may be indirect, for example, affecting regulatory proteins involved in transcription of enzyme-encoding genes (33) or post-translational processes (34). It is also always conceivable that tissues may not be fully primed for premature developmental induction or that the induction process may also require other unknown development-specific factors.…”