Plant phenolics are detoxified by prophenoloxidase in the insect gut.
Plant phenolics are detoxified by prophenoloxidase in the insect gut.
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昆虫肠道中的酚氧化酶原对植物酚类物质进行解毒
DOI：
10.1038/srep16823
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发表时间：
2015-11-23
影响因子：
4.6
通讯作者：
Ling E
中科院分区：
文献类型：
--
作者：
Wu K;Zhang J;Zhang Q;Zhu S;Shao Q;Clark KD;Liu Y;Ling E
植物酚类化合物是一类重要的次生代谢产物，高浓度摄入会对许多动物和昆虫产生毒性。由于大多数昆虫每天都消耗植物酚类化合物，它们可能已经进化出了解毒这些化合物的能力。本文以果蝇（Drosophila melanogaster）、家蚕（Alxmori）和棉铃虫（Helicoverpa armigera）为模型，研究了酚氧化酶原对植物酚类物质的代谢。我们发现，昆虫前肠释放prophenoloxidases到内腔和prophenoloxidase缺失突变体的生存受损时，喂养几种植物酚类物质和茶叶提取物。以l-多巴为模型底物，在大型鳞翅目昆虫中进行的生化测定表明，低水平的l-多巴被酚氧化酶迅速代谢成中间产物。用过量多巴喂养表明，代谢中间体5，6-二羟基吲哚通过直接穿过中肠或通过血淋巴运输到达后肠。在后肠中，5，6-二羟基吲哚被酚氧化酶原进一步氧化。中间体在血腔或中肠中没有毒性。这些结果表明，植物酚类物质对昆虫是无毒的，除非酚氧化酶原基因丢失或酚类物质的水平超过肠道酚氧化酶原的催化活性。
Plant phenolics are a group of important secondary metabolites that are toxic to many animals and insects if ingested at high concentrations. Because most insects consume plant phenolics daily, they have likely evolved the capacity to detoxify these compounds. Here, we usedDrosophila melanogaster,Bombyx moriandHelicoverpa armigeraas models to study the metabolism of plant phenolics by prophenoloxidases. We found that insect foreguts release prophenoloxidases into the lumen and that the survival of prophenoloxidase-deletion mutants was impaired when fed several plant phenolics and tea extracts. Usingl-DOPA as a model substrate, biochemical assays in largeLepidopteraninsects demonstrated that low levels ofl-DOPA are rapidly metabolized into intermediates by phenoloxidases. Feeding with excessl-DOPA showed that the metabolic intermediate 5,6-dihydroxyindole reached the hindgut either by passing directly through the midgut, or by transport through the hemolymph. In the hindgut, 5,6-dihydroxyindole was further oxidized by prophenoloxidases. Intermediates exerted no toxicity in the hemocoel or midgut. These results show that plant phenolics are not toxic to insects unless prophenoloxidase genes are lost or the levels of phenolics exceed the catalytic activity of the gut prophenoloxidases.