Oil Crops Research Institute of Chinese Academy of Agricultural Sciences, Wuhan 430062, China.
J Microbiol Biotechnol. 2013 Oct 28;23(10):1413-21. doi: 10.4014/jmb.1301.01065.
The marine microalga Isochrysis sphaerica is rich in the very-long-chain polyunsaturated fatty acids, including eicosapentaenoic acid (EPA, C20:5ω-3) and docosahexaenoic acid (DHA, C22:6ω-3) that are important to human health. Here, we report a functional characterization of a Δ4-fatty acid desaturase gene (FAD4) from I. sphaerica. IsFAD4 contains a 1,284 bp open reading frame encoding a 427 amino acid polypeptide. The deduced amino sequence comprises three conserved histidine motifs and a cytochrome b5 domain at its N-terminus. Phylogenetic analysis indicated that IsFad4 formed a unique Isochrysis clade distinct from the counterparts of other eukaryotes. Heterologous expression of IsFAD4 in Pichia pastoris showed that IsFad4 was able to desaturate docosapentaenoic acid (DPA) to form DHA, and the rate of converting DPA to DHA was 79.8%. These results throw light on the potential industrial production of specific polyunsaturated fatty acids through IsFAD4 transgenic yeast or oil crops.
海洋微藻球等鞭金藻富含对人体健康非常重要的超长链多不饱和脂肪酸，包括二十碳五烯酸（EPA，C20:5ω-3）和二十二碳六烯酸（DHA，C22:6ω-3）。在这里，我们报道了来自球等鞭金藻的 Δ4-脂肪酸去饱和酶基因（FAD4）的功能特征。IsFAD4 含有一个 1,284 bp 的开放阅读框，编码一个 427 个氨基酸的多肽。推导的氨基酸序列包含三个保守的组氨酸基序和一个 N 端的细胞色素 b5 结构域。系统发育分析表明，IsFad4 形成了一个独特的等鞭金藻分支，与其他真核生物的对应物不同。在巴斯德毕赤酵母中异源表达 IsFAD4 表明，IsFad4 能够使二十二碳五烯酸（DPA）去饱和形成 DHA，并且将 DPA 转化为 DHA 的转化率为 79.8%。这些结果为通过 IsFAD4 转基因酵母或油料作物来潜在地生产特定的多不饱和脂肪酸提供了思路。
