由于进化事件,例如基因丢失和随后由现有基因编码的酶的新和/或亚官能化,硬骨鱼中长链多不饱和脂肪酸(LC-PUFA)的生物合成能力高度多样化。在本研究中,我们已经全面表征了可能参与LC-PUFA生物合成的基因,即一个前端去饱和酶(fads2)和八个脂肪酸延伸酶(elovl1a,elovl1b,elovl4a,elovl4b,elovl5,elovl7,elovl8a和elovl8b)来自两栖硬骨鱼,Ayu甜鱼,多舌肌。功能分析证实Fads2对多种PUFA底物具有Δ6,Δ5和Δ8去饱和酶活性,并且几种Elovl酶对C18-20或C18-22PUFA底物表现出延伸能力。因此,P.altivelis具有完整的酶促能力来合成生理上重要的LC-PUFA,包括花生四烯酸(ARA,20:4n-6),二十碳五烯酸(EPA,20:5n-3)和二十二碳六烯酸(DHA,22:6n-3)来自其C18前体。有趣的是,通过基因组和系统发育分析证实了Altivelis中elovl2基因的丢失。然而,这种限制可能会被替代Elovl酶的功能所克服,比如Elovl1b,迄今为止,在硬骨鱼中还没有功能特征。本研究为相对研究不足的硬骨鱼组的LC-PUFA生物合成提供了新的见解,Osmeriformes(Stomiati),从而增强我们对硬骨鱼中LC-PUFA生物合成基因互补的理解。
The biosynthetic capability of the long-chain polyunsaturated fatty acids (LC-PUFA) in teleosts are highly diversified due to evolutionary events such as gene loss and subsequent neo- and/or sub-functionalisation of enzymes encoded by existing genes. In the present study, we have comprehensively characterised genes potentially involved in LC-PUFA biosynthesis, namely one front-end desaturase (fads2) and eight fatty acid elongases (elovl1a, elovl1b, elovl4a, elovl4b, elovl5, elovl7, elovl8a and elovl8b) from an amphidromous teleost, Ayu sweetfish, Plecoglossus altivelis. Functional analysis confirmed Fads2 with Δ6, Δ5 and Δ8 desaturase activities towards multiple PUFA substrates and several Elovl enzymes exhibited elongation capacities towards C18-20 or C18-22 PUFA substrates. Consequently, P. altivelis possesses a complete enzymatic capability to synthesise physiologically important LC-PUFA including arachidonic acid (ARA, 20:4n-6), eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) from their C18 precursors. Interestingly, the loss of elovl2 gene in P. altivelis was corroborated by genomic and phylogenetic analyses. However, this constraint would possibly be overcome by the function of alternative Elovl enzymes, such as Elovl1b, which has not hitherto been functionally characterised in teleosts. The present study contributes novel insights into LC-PUFA biosynthesis in the relatively understudied teleost group, Osmeriformes (Stomiati), thereby enhancing our understanding of the complement of LC-PUFA biosynthetic genes within teleosts.