Eur. J. Entomol. 94 (1): 57-65, 1997
Ecdysone 20-hydroxylation in Manduca sexta (Lepidoptera: Sphingidae) midgut: Development-related changes of mitochondrial and microsomal ecdysone 20-monooxygenase activities in the fifth larval instar
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In the mid fifth-larval-instar tobacco hornworm, Manduca sexta, the midgut has high ecdysone 20-monooxygenase (E20MO) activity, with a peak at the onset of wandering on day five. Activities of E20MO, present both in mitochondria and in microsomes, were determined around the time of the peak. During the day preceding the peak the microsomal E20MO increased 60-fold (total activity) or 115-fold (specific activity), and it decreased to one half or less of the peak activities within two days after the peak. The mitochondrial E20MO increased only 1.3 to 2.4-fold (total and specific activities, respectively) before the peak, but declined more rapidly than the microsomal E20MO after the peak. It is concluded that mitochondrial and microsomal E20MO activities are controlled independently and that changes in the physiological rate of ecdysone 20-hydroxylation are effected primarily by changes of the microsomal E20MO activities.
Keywords: Tobacco hornworm, Manduca sexta, midgut, 20-hydroxylation, ecdysone 20-monooxygenase, ecdysone 26-monooxygenase, microsomes, mitochondria, cytochrome P-450
Accepted: March 18, 1996; Published: March 10, 1997 Show citation
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