Kabeya Naoki, Sanz-Jorquera Alicia, Carboni Stefano, Davie Andrew, Oboh Angela, Monroig Oscar
Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, Scotland, United Kingdom.
PLoS One. 2017 Jan 4;12(1):e0169374. doi: 10.1371/journal.pone.0169374. eCollection 2017.
Sea urchins are broadly recognised as a delicacy and their quality as food for humans is highly influenced by their diet. Lipids in general and the long-chain polyunsaturated fatty acids (LC-PUFA) in particular, are essential nutrients that determine not only the nutritional value of sea urchins but also guarantee normal growth and reproduction in captivity. The contribution of endogenous production (biosynthesis) of LC-PUFA in sea urchins remained unknown. Using Paracentrotus lividus as our model species, we aimed to characterise both molecularly and functionally the repertoire of fatty acyl desaturases (Fads), key enzymes in the biosynthesis of LC-PUFA, in sea urchins. Three Fads, namely FadsA, FadsC1 and FadsC2, were characterised. The phylogenetic analyses suggested that the repertoire of Fads within the Echinodermata phylum varies among classes. On one hand, orthologues of the P. lividus FadsA were found in other echinoderm classes including starfishes, brittle stars and sea cucumbers, thus suggesting that this desaturase is virtually present in all echinoderms. Contrarily, the FadsC appears to be sea urchin-specific desaturase. Finally, a further desaturase termed as FadsB exists in starfishes, brittle stars and sea cucumbers, but appears to be missing in sea urchins. The functional characterisation of the P. lividus Fads confirmed that the FadsA was a Δ5 desaturase with activity towards saturated and polyunsaturated fatty acids (FA). Moreover, our experiments confirmed that FadsA plays a role in the biosynthesis of non-methylene interrupted FA, a group of compounds typically found in marine invertebrates. On the other hand, both FadsC desaturases from P. lividus showed Δ8 activity. The present results demonstrate that P. lividus possesses desaturases that account for all the desaturation reactions required to biosynthesis the physiological essential eicosapentaenoic and arachidonic acids through the so-called "Δ8 pathway".
海胆被广泛认为是一种美味佳肴，其作为人类食物的品质受到其饮食的高度影响。一般来说，脂质，特别是长链多不饱和脂肪酸（LC-PUFA），是必需营养素，不仅决定了海胆的营养价值，还保证了圈养中海胆的正常生长和繁殖。海胆中LC-PUFA的内源性产生（生物合成）的贡献仍然未知。我们以紫球海胆（Paracentrotus lividus）作为模型物种，旨在从分子和功能上表征海胆中脂肪酸去饱和酶（Fads）的全部组成，Fads是LC-PUFA生物合成中的关键酶。我们表征了三种Fads，即FadsA、FadsC1和FadsC2。系统发育分析表明，棘皮动物门内Fads的全部组成在不同类别之间有所不同。一方面，在包括海星、蛇尾和海参在内的其他棘皮动物类别中发现了紫球海胆FadsA的直系同源物，因此表明这种去饱和酶实际上存在于所有棘皮动物中。相反，FadsC似乎是海胆特有的去饱和酶。最后，海星、蛇尾和海参中存在另一种称为FadsB的去饱和酶，但海胆中似乎没有。紫球海胆Fads的功能表征证实，FadsA是一种Δ5去饱和酶，对饱和脂肪酸和多不饱和脂肪酸（FA）具有活性。此外，我们的实验证实，FadsA在非亚甲基中断脂肪酸的生物合成中起作用，非亚甲基中断脂肪酸是一组通常在海洋无脊椎动物中发现的化合物。另一方面，紫球海胆的两种FadsC去饱和酶都表现出Δ8活性。目前的结果表明，紫球海胆拥有去饱和酶，这些去饱和酶通过所谓的“Δ8途径”完成生物合成生理必需的二十碳五烯酸和花生四烯酸所需的所有去饱和反应。
