The effect of alpha-ecdysone and phenobarbital on the alpha-ecdysone 20-monooxygenase of house fly larva.
The NADPH-dependent cytochrome P-450 20-monooxygenation of alpha-ecdysone is catalyzed both by mitochondria and microsomes isolated from Musca domestica, L. larvae, but about 50% of the activity is associated with mitochondria and 37% with microsomes. The mitochondrial activity is increased by pretreatment with alpha-ecdysone with a concomitant decrease in Km values. This effect is not observed in microsomes. Induction with phenobarbital represses the mitochondrial 20-monooxygenase but does not change the microsomal activity, although a large increase in cytochrome P-450 is observed in the latter fraction. It is concluded that only the mitochondrial 20-monooxygenase appears to be regulated by alpha-ecdysone which suggests that mitochondrial cytochrome P-450 forms are involved in the moulting phenomenon; whereas, microsomal cytochrome P-450 activity may be of a nonspecific nature and not relevant to development.
Department of Zoology, University of Georgia, Athens 30602.
J
J
Srivatsan
T
T
Kuwahara
M
M
Agosin
D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D004440:Ecdysone / Q000494:pharmacology*; D004790:Enzyme Induction; D006793:Houseflies / Q000201:enzymology*; D007700:Kinetics; D008861:Microsomes / Q000201:enzymology; D008928:Mitochondria / Q000201:enzymology; D010634:Phenobarbital / Q000494:pharmacology*; D013250:Steroid Hydroxylases / Q000378:metabolism*
D004440:Ecdysone; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; C020095:ecdysone 20-hydroxylase; D010634:Phenobarbital