Artemia nauplii are widely used as live preys for feeding early life-cycle stages of marine finfish and shrimp. However, a major drawback associated to using Artemia is their deficient nutritional value for marine larvae that is primarily linked to suboptimal levels of long-chain polyunsaturated fatty acids (LC-PUFA), essential nutrients that guarantee normal growth and development of animals. While common marine hatchery procedures involve enrichment processes to address such nutritional deficiencies, the specific drivers accounting for the naturally occurring variability in LC-PUFA of Artemia are largely unknown. Biosynthesis, along diet, is one of the main factors determining the LC-PUFA profiles in animals and it depends upon the repertoire and function of fatty acyl elongases and desaturases existing in a particular species. The aim of this study was the molecular and functional characterisation of all elongase and desaturase enzymes involved in the LC-PUFA biosynthesis from Artemia franciscana, arguably the most commonly used Artemia species. Seven out of eight elongases (termed “Elo1-8”) found in A. franciscana had distinctive features of LC-PUFA biosynthesising elongases. Consistently, functional assays showed these elongases were able to elongate multiple substrates and thus enabling A. franciscana to perform all elongation reactions of the LC-PUFA biosynthetic pathways. While all seven functionally characterised elongases from A. franciscana showed activity towards multiple substrates including C₁₈ to C₂₂ polyunsaturated fatty acids, particularly high activity was detected for the Elovl8 orthologue (termed herein as “Elo7”). Additionally, A. franciscana was found to have three genes of the so-called “first” desaturases (“Des1-3”), and lack other key LC-PUFA biosynthesising desaturases such as methyl-end and front-end desaturases. Two desaturases have the expected ∆9 desaturase activity, whereas a third one showed ∆12 activity. Neither methyl-end nor front-end desaturases were found in A. franciscana. In conclusion, this study demonstrated that A. franciscana has high elongation capacity but its overall LC-PUFA biosynthesis can be regarded as limited due to the lack of an adequate complement of fatty acyl desaturases in its genome.

卤虫无节幼体被广泛用作活的猎物，用于喂养生命周期早期的海洋有鳍鱼和虾。然而，与使用卤虫有关的一个主要缺点是它们对海洋幼虫的营养价值不足，这主要与长链多不饱和脂肪酸 (LC-PUFA) 水平不佳有关，而长链多不饱和脂肪酸 (LC-PUFA) 是保证动物正常生长和发育的必需营养素。虽然常见的海洋孵化程序涉及解决此类营养缺乏的富集过程，但解释卤虫LC-PUFA 自然发生变异的具体驱动因素很大程度上是未知的。沿着饮食进行的生物合成是决定动物中 LC-PUFA 谱的主要因素之一，它取决于特定物种中存在的脂肪酰基延伸酶和去饱和酶的全部内容和功能。本研究的目的是对参与来自Artemia franciscana的 LC-PUFA 生物合成的所有延伸酶和去饱和酶的分子和功能表征，可以说是最常用的卤虫物种。在A. franciscana中发现的八种延伸酶中的七种（称为“Elo1-8”）具有 LC-PUFA 生物合成延伸酶的独特特征。一致地，功能测定表明这些延长酶能够延长多种底物，从而使A. franciscana进行 LC-PUFA 生物合成途径的所有延伸反应。虽然来自A. franciscana的所有七种功能表征的延伸酶都显示出对包括 C ₁₈至 C ₂₂多不饱和脂肪酸在内的多种底物的活性，但对于 Elovl8 直系同源物（本文称为“Elo7”）检测到特别高的活性。此外，发现A. franciscana具有所谓的“第一”去饱和酶（“Des1-3”）的三个基因，并且缺乏其他关键的 LC-PUFA 生物合成去饱和酶，例如甲基末端和前端去饱和酶。两种去饱和酶具有预期的 Δ9 去饱和酶活性，而第三种则具有 Δ12 活性。在A. franciscana中均未发现甲基末端去饱和酶和前端去饱和酶. 总之，本研究表明A. franciscana具有高延伸能力，但由于其基因组中缺乏足够的脂肪酰基去饱和酶补充，其整体 LC-PUFA 生物合成可被视为有限。