Ecdysone 20-hydroxylation in Manduca sexta midgut: Kinetic parameters of mitochondrial and microsomal ecdysone 20-monooxygenases

✍ Scribed by Gunter F. Weirich; Virginia P. Williams; Mark F. Feldlaufer

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 499 KB
• Volume: 31
• Category: Article
• ISSN: 0739-4462
• DOI: 10.1002/(sici)1520-6327(1996)31:3<305::aid-arch5>3.0.co;2-w

✦ Synopsis

The larval midgut of the tobacco hornworm, Manduca sexta, has high ecdysone 20-monooxygenase (EZOMO) activity, located both in the mitochondria and in the microsomes. The apparent kinetic parameters for E20MO in mitochondria and microsomes were determined. The K , s (for ecdysone) of the rnitochondrial and microsomal enzymes were 1.63 x 1 0-5 and 3.67 x 1 O-' M, respectively. The V, , , was 82.7 prnol/min/rng protein for mitochondria and 32.0 pmol/min/mg protein for microsomes. Although the mitochondria1 E20MO has the higher V , , , ,

it is only one-eighth to one-tenth as active as the rnicrosornal enzyme. It is concluded that the rnicrosornal E20MO is the primary, if not the only, enzyme involved in ecdysone 20-hydroxylation in M. 5exta midgut.