高度不饱和脂肪酸（HUFA）对人和动物体的健康具有重要功能。鱼类是HUFA的重要来源，但不同鱼类的HUFA合成能力不同，主要与HUFA合成关键酶- - 特别是脂肪酸去饱和酶（FAD）的种类和活性的差异有关。鱼类FAD具功能多样性和n-3底物偏好性的特点，但目前尚缺乏相关机制的研究。本项目拟选择几种典型的FAD（黄斑蓝子鱼Δ6/Δ5及Δ4、斑马鱼Δ6/Δ5、军曹鱼Δ6以及偏好n-6底物的小鼠Δ6去饱和酶）为研究对象，通过对不同FAD一级结构的序列比对、拓扑结构预测、基因定向改造和酶活性鉴定等方面的系统比较、分析，以阐明酶的结构与功能的关系，并揭示鱼类FAD的底物识别及n-3底物偏好性的分子基础和机制。本项目首次聚焦FAD的功能特性，项目成果不仅对于丰富鱼类分子营养学内容具有重要的理论意义，也有助于揭示鱼类富集n-3 HUFA的分子机理，还可为鱼类FAD基因资源的发掘和应用等提供理论依据。

Highly unsaturated fatty acids (HUFA) are healthy benefit to human and most animals. Fish are mainly source of n-3 HUFAs, but owing to complex key enzymes, especially fatty acid desaturase, there are huge differences HUFA biosynthesis abilities in different speciec fish. Two remarkable characteristics of fatty acid desaturases in HUFA biosynthesis are functional diversity and n-3 substrate preference in fish, which mechanism should be studied. In this project, we focus regioselectivity and substrate preference of several desaturases from fish and mammalian, such asΔ6/Δ5 and Δ4 desaturases of rabbitfish, Δ6/Δ5 desaturase of zebrafish, Δ6 desaturase of cobia, and Δ6 desaturase of mouse which has n-6 substrate preference. First, study the relationship of primary structure and molecular functional characteristics specific regioselectivity and n-3 substrate preference of desaturase in fish by performing directional transformation with quantitative heterogeous functional characterization in Saccharomyces cerevisiae. Then, explain the molecular basis of regioselectivity and substrate perference of desaturases by summarizing conservative region or concensus sequence, predict a structure model to explain mechanism of regioselectivity and n-3 substrate preference of fish desaturases. This project is the first time focus molecular character of desaturase. The prespective achievements would enrich research contents of fish molecular nutriology, set up bases for studying relationship of structure and function of member-bound fatty acid desaturase, understand pathway and mechenism of HUFA biosynthesis in fish, and reveal n-3 HUFA enrichment mechanism in fish, as well as provide the theoretical foundation to get new gene, develop new theroy, and perform transformation in expectation.