Centro Oceanográfico de Canarias, Instituto Español de Oceanografía, Santa Cruz de Tenerife, Tenerife, Spain.
Department of Aquatic Bioscience, The University of Tokyo, Yayoi, Bunkyo-ku, Tokyo, Japan.
Biochim Biophys Acta Mol Cell Biol Lipids. 2019 Aug;1864(8):1134-1144. doi: 10.1016/j.bbalip.2019.04.012. Epub 2019 Apr 30.
The interest in understanding the capacity of aquatic invertebrates to biosynthesise omega-3 (ω3) long-chain (≥C) polyunsaturated fatty acids (LC-PUFA) has increased in recent years. Using the common octopus Octopus vulgaris as a model species, we previously characterised a ∆5 desaturase and two elongases (i.e. Elovl2/5 and Elovl4) involved in the biosynthesis of LC-PUFA in molluscs. The aim of this study was to characterise both molecularly and functionally, two methyl-end (or ωx) desaturases that have been long regarded to be absent in most animals. O. vulgaris possess two ωx desaturase genes encoding enzymes with ∆12 and ω3 regioselectivities enabling the de novo biosynthesis of the C PUFA 18:2ω6 (LA, linoleic acid) and 18:3ω3 (ALA, α-linolenic acid), generally regarded as dietary essential for animals. The O. vulgaris ∆12 desaturase ("ωx2") mediates the conversion of 18:1ω9 (oleic acid) into LA, and subsequently, the ω3 desaturase ("ωx1") catalyses the ∆15 desaturation from LA to ALA. Additionally, the O. vulgaris ω3 desaturase has ∆17 capacity towards a variety of C ω6 PUFA that are converted to their ω3 PUFA products. Particularly relevant was the affinity of the ω3 desaturase towards 20:4ω6 (ARA, arachidonic acid) to produce 20:5ω3 (EPA, eicosapentaenoic acid), as supported by yeast heterologous expression, and enzymatic activity exhibited in vivo when paralarvae were incubated in the presence of [1-C]20:4ω6. These results confirmed that several routes enabling EPA biosynthesis are operative in O. vulgaris whereas ARA and docosahexaenoic acid (DHA, 22:6ω3) should be considered essential fatty acids since endogenous production appears to be limited.
近年来，人们对了解水生无脊椎动物生物合成 ω-3（ω3）长链（≥C）多不饱和脂肪酸（LC-PUFA）的能力产生了浓厚的兴趣。本文以普通章鱼（Octopus vulgaris）为模式物种，之前已对参与软体动物 LC-PUFA 生物合成的 ∆5 去饱和酶和两种延伸酶（即 Elovl2/5 和 Elovl4）进行了特征描述。本研究旨在从分子和功能上对两种甲基端（或 ωx）去饱和酶进行研究，这些酶在大多数动物中被认为长期缺失。章鱼 O. vulgaris 拥有两种 ωx 去饱和酶基因，编码具有 ∆12 和 ω3 区域选择性的酶，使 C PUFA 18:2ω6（LA，亚油酸）和 18:3ω3（ALA，α-亚麻酸）的从头生物合成成为可能，这些脂肪酸通常被认为是动物的饮食必需脂肪酸。章鱼 O. vulgaris 的 ∆12 去饱和酶（"ωx2"）介导 18:1ω9（油酸）向 LA 的转化，随后，ω3 去饱和酶（"ωx1"）催化 LA 向 ALA 的 ∆15 去饱和。此外，章鱼 O. vulgaris 的 ω3 去饱和酶对各种 C ω6 PUFA 具有 ∆17 能力，这些脂肪酸转化为其 ω3 PUFA 产物。特别值得注意的是，ω3 去饱和酶对 20:4ω6（ARA，花生四烯酸）的亲和力，使其能够产生 20:5ω3（EPA，二十碳五烯酸），这一结果得到了酵母异源表达和幼虫在存在 [1-C]20:4ω6 时体内酶活性的支持。这些结果证实，几种使 EPA 生物合成的途径在 O. vulgaris 中是可行的，而 ARA 和二十二碳六烯酸（DHA，22:6ω3）应该被认为是必需脂肪酸，因为内源性产生似乎是有限的。
