Metabolism of Isoleucine to Insect Juvenile Hormone II via Propionyl-Coenzyme A

研究表明，异亮氨酸和缬氨酸为乙基支化幼激素（JHs）的生物合成提供了丙酸单位。不容易代谢这些物质的昆虫（鳞翅目昆虫）会分泌丙酸酯和乙基分支的JHs。本研究将扩展这些研究，并确定是什么允许CA违反倍半萜类生物合成规则，并将丙酰辅酶a纳入该途径。新陈代谢ıU-14c！异亮氨酸将在几种产生乙基支链的JHs和只产生jhiii的昆虫组织中进行检验。这些数据对于解释物种之间的代谢差异很重要。另外，新陈代谢ıU-14c！还将研究分离线粒体中的异亮氨酸。这项工作将确定是否有一个有效的运输系统，从线粒体出口丙酰辅酶a。肉毒碱丙酰转移酶和柠檬酸甲酯的形成将被视为丙酰辅酶a运输的可能途径。如果这种现象不能用丙酸运输的独特系统来解释，那么将研究某些酶可能位于不同的亚细胞器中的可能性，而不是它们通常存在的亚细胞器。幼体激素是一组结构相关的化合物，由昆虫类成员分泌，具有形态发生和促性腺激素活性。重要的是要了解代谢途径的基本知识，以了解昆虫为什么以及如何能够合成这些激素。了解这一途径的生化细节可以为合成专门抑制它的化学物质指明方向。这些化学物质可能是抗激素（因此可能是特定的杀虫剂），与包括飞蛾在内的昆虫相同，飞蛾是对作物最具破坏性的害虫之一。

It has been shown that isoleucine and valine supply propionate units used specifically for the biosynthesis of the ethyl-branched juvenile hormones (JHs). Insect corpora allata (CA) which do not metabolize them readily (the CA of Lepidoptera) secrete propionate and ethyl-branched JHs. This research will extend these studies and determine what allows the CA to violate the rules of sesquiterpenoid biosynthesis and to incorporate propionyl-CoA into this pathway. The metabolism of ıU-14c! isoleucine will be examined in several tissues of insects which make the ethyl-branched JHs vs. those that produce only JH III. These data are important for interpreting metabolic differences between species. In addition, the metabolism of ıU-14c! isoleucine in isolated mitochondria will also be studied. This work will determine whether or not there is an efficient transport system for exporting propionyl-CoA from the mitochondria. Carnitine propionyl transferase and methyl citrate formation will be examined as likely possibilities for propionyl CoA transport. If this phenomenon cannot be explained by a unique system for propionate transport, the possibility will be investigated that certain enzymes might be located in different subcellular organelles than those in which they are generally held to exist. Juvenile hormones are a group of structurally related compounds secreted by members of the class Insecta and which possess morphogenetic and gonadotropic activity. It is important to have a basic knowledge of the metabolic pathways involved to understand why and how insects are able to synthesize these hormones. Knowledge of the biochemical details of this pathway could point the way towards synthesis of chemicals which specifically inhibit it. These chemicals would be antihormones (and probably, therefore, specific insecticides) to the order of insects that includes moths, which are some of the most damaging of crop pests.