Chen J H, Kabbouh M, Fisher M J, Rees H H
Department of Biochemistry, University of Liverpool, U.K.
Biochem J. 1994 Jul 1;301 ( Pt 1)(Pt 1):89-95. doi: 10.1042/bj3010089.
Treatment of the last-instar larvae of the cotton leafworm (Spodoptera littoralis) with ecdysteroids (moulting hormones) results in the induction of an ecdysteroid-inactivation pathway. Administration of ecdysone, 20-hydroxyecdysone or an ecdysteroid agonist, RH 5849, leads to induction of an ecdysteroid 26-hydroxylase activity. This induction occurred in both early sixth-instar larvae and in older larvae which had been head-ligated to prevent the normal developmental increase in ecdysone 20-mono-oxygenase activity. The induction of 26-hydroxylase activity requires both RNA and protein synthesis, as demonstrated by experiments involving actinomycin D and cycloheximide. The 26-aldehyde derivative of ecdysone and ecdyson-26-oic acid were also formed from ecdysone in the RH 5849-induced systems. Formation of the aldehyde and the corresponding 26-oic acid (ecdysonoic acid) from 26-hydroxyecdysone was directly demonstrated in a cell-free system, thus establishing the following inactivation pathway: Ecdysteroid-->26-hydroxyecdysteroid-->ecdysteroid 26-aldehyde-->ecdysteroid 26-oic acid.
用蜕皮甾类（蜕皮激素）处理棉铃虫（埃及棉叶虫）的末龄幼虫会导致蜕皮甾类失活途径的诱导。施用蜕皮激素、20-羟基蜕皮激素或一种蜕皮甾类激动剂RH 5849会导致蜕皮甾类26-羟化酶活性的诱导。这种诱导在早期六龄幼虫和已进行头部结扎以防止蜕皮激素20-单加氧酶活性正常发育性增加的老龄幼虫中均会发生。如涉及放线菌素D和环己酰亚胺的实验所示，26-羟化酶活性的诱导需要RNA和蛋白质合成。在RH 5849诱导的系统中，蜕皮激素的26-醛衍生物和蜕皮甾酮-26-酸也由蜕皮激素形成。在无细胞系统中直接证明了从26-羟基蜕皮激素形成醛和相应的26-酸（蜕皮甾酮酸），从而建立了以下失活途径：蜕皮甾类→26-羟基蜕皮甾类→蜕皮甾类26-醛→蜕皮甾类26-酸。
