a ICAR - CIFRI, Barrackpore , India.
b ICAR - Krishi Anusandhan Bhawan I , New Delhi , India.
Anim Biotechnol. 2018 Jul 3;29(3):161-173. doi: 10.1080/10495398.2017.1332639. Epub 2017 Jun 28.
Fish are an important source of highly unsaturated fatty acids (HUFA) such as eicosapentaenoic acid EPA (20:5 n-3) and docosahexaenoic acid DHA (22:6 n-3) and play a significant role in human nutrition. The fatty acyl delta6-desaturase (Δ6 desaturase) is a rate-limiting enzyme in the biosynthetic pathway of highly unsaturated fatty acids (HUFA) that converts polyunsaturated fatty acids (PUFA) such as linoleic (18:2n-6) and α-linolenic (18:3n-3) acids into HUFA. In this study, fatty acyl Δ6 desaturase was identified from pangasius (Pangasianodon hypophthalmus) and further analyzed for sequenced-based characterization and 3D structural conformation. Sequenced-based analysis revealed some important secondary information such as physicochemical property. e.g., isoelectric point, extinction coefficient, aliphatic index, and grand average hydropathy, among others, and also post-translational modification sites were identified. An evolutionary-conserved stretch of amino acid residue and a functionally significant conserved structural ancestor, N-terminal cytochrome b5 and membrane FADS-like superfamily, were identified. Protein association analysis showed a high confidence score with acyl-CoA synthetase, elovl5, elovl2, and phospholipase A2. Herein, we report, for the first time, a 3D native structure of Δ6 desaturase protein by homology modeling approach; molecular docking analysis was performed with linoleic (18:2n-6) and α-linolenic (18:3n-3) acids, which are the two key substrates in the HUFA biosynthetic pathway. This work provides insight into the structural and functional characterization of Δ6 desaturase, which is involved in HUFA biosynthesis as a rate-limiting enzyme.
鱼类是高度不饱和脂肪酸（HUFA）如二十碳五烯酸（EPA，20:5n-3）和二十二碳六烯酸（DHA，22:6n-3）的重要来源，在人类营养中发挥着重要作用。脂肪酸 Δ6 去饱和酶（Δ6 去饱和酶）是高度不饱和脂肪酸（HUFA）生物合成途径中的限速酶，可将多不饱和脂肪酸（PUFA）如亚油酸（18:2n-6）和α-亚麻酸（18:3n-3）转化为 HUFA。在这项研究中，从 Pangasianodon hypophthalmus 鉴定出脂肪酸 Δ6 去饱和酶，并进一步基于测序进行了特征分析和 3D 结构构象分析。基于测序的分析揭示了一些重要的二级信息，如等电点、消光系数、脂肪指数和平均亲水性等，还鉴定了翻译后修饰位点。鉴定了一个氨基酸残基的进化保守片段和一个功能上重要的保守结构祖先，N 端细胞色素 b5 和膜 FADS 样超家族。蛋白质关联分析显示与酰基辅酶 A 合成酶、elovl5、elovl2 和磷脂酶 A2 具有高置信度评分。本文首次通过同源建模方法报告了 Δ6 去饱和酶蛋白的 3D 天然结构；进行了分子对接分析，使用了亚油酸（18:2n-6）和α-亚麻酸（18:3n-3），这两种酸是 HUFA 生物合成途径中的两个关键底物。这项工作深入了解了作为限速酶参与 HUFA 生物合成的 Δ6 去饱和酶的结构和功能特征。
