C. Kappler, M. Kabbouh, C. Hétru
Dec 1, 1988
Citations
2
Influential Citations
68
Citations
Journal
Journal of steroid biochemistry
Abstract
It is most generally accepted that the last three enzymatic reactions in the biosynthetic pathway of ecdysone are, in this order, the hydroxylations at positions C-25, C-22 and C-2. Using high specific activity tritiated ecdysone precursors (2,22,25-trideoxyecdysone, 2,22-dideoxyecdysone and 2-deoxyecdysone) we have characterized the hydroxylases involved in these reactions, in the major biosynthetic tissue of ecdysone, i.e. the prothoracic glands. We show that C-2 hydroxylase is a mitochondrial oxygenase which differs from conventional cytochrome P-450-dependent monooxygenases by its relative insensitivity to CO. In contrast, C-22 and C-25 hydroxylases appear as classical cytochrome P-450 monooxygenases; C-22 hydroxylase is a mitochondrial enzyme whereas our data point to a microsomal localization of the C-25 hydroxylase.