Highly Unsaturated Fatty Acid Synthesis in Atlantic Salmon: Characterization of ELOVL5-and ELOVL2-like Elongases
Highly Unsaturated Fatty Acid Synthesis in Atlantic Salmon: Characterization of ELOVL5-and ELOVL2-like Elongases
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DOI：
10.1007/s10126-009-9179-0
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发表时间：
2009-10-01
影响因子：
3
通讯作者：
Tocher, Douglas R.
中科院分区：
文献类型：
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作者：
Morais, Sofia;Monroig, Oscar;Tocher, Douglas R.
鱼类生物合成n-3长链多不饱和脂肪酸（LC-PUFA）、二十碳五烯酸（EPA）和二十二碳六烯酸（DHA）的能力各不相同，这些酸对高等脊椎动物的健康至关重要。LC-PUFA的合成涉及酶介导的脂肪酰基去饱和和延伸。以前，已经从大西洋鲑鱼中克隆了现在称为elovl 5a的延长酶的互补DNA（cDNA）。在这里，我们报告两个新的延伸酶cDNA的克隆：第二elovl 5 b延伸酶，对应于294个氨基酸（aa）的蛋白质，和elovl 2样延伸酶，编码287个氨基酸的蛋白质，其特征在于第一次在非哺乳动物脊椎动物。酵母中的异源表达显示鲑鱼Elovl 5 b延长C18和C20 PUFA，对C22具有低活性，而Elovl 2延长C20和C22 PUFA，对C18 PUFA具有较低活性。所有三种转录物均在肠和肝脏中显示出主要表达，其次是脑。延伸酶表达差异营养调节。与饲喂鱼油（FO）的鱼相比，饲喂植物油（VO）的鲑鱼的肝脏中elovl 5 b和特别是elovl 2（但不是elovl 5a）转录物的水平显著增加。肠道表达显示出类似的模式。系统发育比较表明，与鲑鱼和斑马鱼相比，棘鳍鱼类缺乏elovl 2，这与它们生物合成LC-PUFA和适应VO膳食包含的能力可忽略不计（与主要的淡水鲑鱼相比）是一致的。因此，鲑鱼中elovl 2的存在解释了该物种生物合成LC-PUFA的能力，并且可以提供生物技术工具以在转基因生物中产生增强水平的LC-PUFA，特别是DHA。
Fish species vary in their capacity to biosynthesize the n-3 long-chain polyunsaturated fatty acids (LC-PUFA), eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids that are crucial to the health of higher vertebrates. The synthesis of LC-PUFA involves enzyme-mediated fatty acyl desaturation and elongation. Previously, a complementary DNA (cDNA) for an elongase, now termed elovl5a, had been cloned from Atlantic salmon. Here, we report on the cloning of two new elongase cDNAs: a second elovl5b elongase, corresponding to a 294-amino-acid (aa) protein, and an elovl2-like elongase, coding for a 287-aa protein, characterized for the first time in a nonmammalian vertebrate. Heterologous expression in yeast showed that the salmon Elovl5b elongated C18 and C20 PUFA, with low activity towards C22, while Elovl2 elongated C20 and C22 PUFA with lower activity towards C18 PUFA. All three transcripts showed predominant expression in the intestine and liver, followed by the brain. Elongase expression showed differential nutritional regulation. Levels of elovl5b and particularly of elovl2, but not of elovl5a, transcripts were significantly increased in liver of salmon fed vegetable oils (VO) compared to fish fed fish oil (FO). Intestinal expression showed a similar pattern. Phylogenetic comparisons indicate that, in contrast to salmon and zebra fish, Acanthopterygian fish species lack elovl2 which is consistent with their negligible ability to biosynthesize LC-PUFA and to adapt to VO dietary inclusion, compared to predominantly freshwater salmonids. Thus, the presence of elovl2 in salmon explains the ability of this species to biosynthesize LC-PUFA and may provide a biotechnological tool to produce enhanced levels of LC-PUFA, particularly DHA, in transgenic organisms.