Instituto de Acuicultura Torre de la Sal (IATS), CSIC, 12595 Ribera de Cabanes, Castellón, Spain.
The Scottish Oceans Institute, School of Biology, University of St. Andrews, St Andrews, Fife KY16 8LB, UK.
Biochim Biophys Acta Mol Cell Biol Lipids. 2023 Oct;1868(10):159377. doi: 10.1016/j.bbalip.2023.159377. Epub 2023 Jul 29.
Aquatic single-cell organisms have long been believed to be unique primary producers of omega-3 long-chain (≥C) polyunsaturated fatty acids (ω3 LC-PUFA). Multiple invertebrates including annelids have been discovered to possess methyl-end desaturases enabling key steps in the de novo synthesis of ω3 LC-PUFA, and thus potentially contributing to their production in the ocean. Along methyl-end desaturases, the repertoire and function of further LC-PUFA biosynthesising enzymes is largely missing in Annelida. In this study we examined the front-end desaturase gene repertoire across the phylum Annelida, from Polychaeta and Clitellata, major classes of annelids comprising most annelid diversity. We further characterised the functions of the encoded enzymes in selected representative species by using a heterologous expression system based in yeast, demonstrating that functions of Annelida front-end desaturases have highly diversified during their expansion in both terrestrial and aquatic ecosystems. We concluded that annelids possess at least two front-end desaturases with Δ5 and Δ6Δ8 desaturase regioselectivities, enabling all the desaturation reactions required to convert the C precursors into the physiologically relevant LC-PUFA such as eicosapentaenoic and arachidonic acids, but not docosahexaenoic acid. Such a gene complement is conserved across the different taxonomic groups within Annelida.
水生单细胞生物长期以来一直被认为是 ω-3 长链（≥C）多不饱和脂肪酸（ω3 LC-PUFA）的唯一初级生产者。已经发现多种无脊椎动物，包括环节动物，它们具有甲基末端去饱和酶，能够在 ω3 LC-PUFA 的从头合成中发挥关键作用，从而有可能促进海洋中 ω3 LC-PUFA 的产生。除了甲基末端去饱和酶外，环节动物在 LC-PUFA 生物合成酶方面的 repertoire 和功能在很大程度上是缺失的。在这项研究中，我们检查了环节动物门的前端去饱和酶基因 repertoire，包括多毛类和蛭形类，它们是构成大多数环节动物多样性的主要类群。我们进一步通过基于酵母的异源表达系统，对选定代表性物种中编码酶的功能进行了表征，证明了 Annelida 前端去饱和酶在其在陆地和水生生态系统中的扩张过程中具有高度多样化的功能。我们得出结论，环节动物至少具有两种前端去饱和酶，具有 Δ5 和 Δ6Δ8 去饱和酶的区域选择性，能够将 C 前体转化为生理相关的 LC-PUFA，如二十碳五烯酸和花生四烯酸，但不能转化为二十二碳六烯酸。这种基因补充在环节动物的不同分类群中是保守的。
