鱼类脂肪酸合成关键酶的鉴定与进化分析
毕业论文关键词：鱼类；脂肪酸合成；关键酶；进化
Molecular Characterization and Evolution of the Key Enzymes Involved in Fatty Acid Biosynthesis in Fish
Abstract: As a carboxylic acid, Fatty acid can be found in a variety of esters, palying important roles in cell structure, energy transport and storage, hormone synthesis intermediates and so on. Fatty acid synthesis is required for normal biological functions in fish. But the key enzymes of this pathway remain unknown. In this study, the sequence and evolution of ACACA, ACACB, FASN, OLAH, ACSL1a, ACSL1b and ACSBG, which are mainly involved in fatty acid biosynthesis, were analyzed in detail. All the enzymes could be pided into five groups, and ACACA/ACACB and ACSL1a/ACSL1b belong to the same group. The conserved motif organizations were shared by the same group, but different motif organizations were displayed in different group. The same enzyme usually was under negative selection, and this could be associated with functional constraint. Branch model had revealed heterogeneous evolutionary rate found in different branches from the phylogenic tree of the same enzyme. The results provide useful clues for functionally investigating the biological roles of key enzymes from fatty acid biosynthesis in fish.
Key words: Fish, Fatty acid synthesis, Key enzyme, Evolution
目 录
摘要 1
引言 2
1数据与方法 3
1.1物种抽样与数据来源 3
1.2 数据下载与整理 4
1.3 鱼类脂肪酸合成关键酶基因的进化分析 4
1.4 鱼类脂肪酸合成关键酶蛋白的保守基序分析 4
1.5 鱼类脂肪酸合成关键酶的选择压力 4
2 结果与分析 5
2.1 鱼类脂肪酸合成关键酶基因的鉴定 5
2.2 鱼类脂肪酸合成关键酶基因的系统进化关系 5
2.3 鱼类脂肪酸合成关键酶蛋白的序列特征 6
2.4 基于位点模型检测鱼类脂肪酸合成酶的选择压力 8
2.5 基于分支模型检测鱼类脂肪酸合成关键酶的选择压力 11
3 讨论与结论 13
参考文献 14
附录 16
致谢 17
鱼类脂肪酸合成关键酶的鉴定与进化分析
引言
脂肪酸(fatty acid)是属于长烃链的羧酸，常以酯的形式存在，游离态的脂肪酸在自然界很罕见。大多数脂肪酸含偶数个碳原子，因为它们通常由2碳单位(乙酰-COA)生物合成[1]。高等动物与植物中最丰富的脂肪酸是16或18个碳原子的，如软脂酸、亚油酸和硬脂酸[2]。动植物脂质的脂肪酸中，超过半数含不饱和的脂肪酸，且常为多双键不饱和脂肪酸。动物能合成饱和脂肪酸和只含1个双键的不饱和脂肪酸，含有2个或2个以上双键的多不饱和脂肪酸则必须从植物中获取(后者称为必需脂肪酸)，其中亚油酸和亚麻酸最重要。脂肪酸是细胞能量运输和储存所必须的，也是细胞结构的重要组成成分，又在激素合成过程中有着不可或缺的作用[3]。总之，脂肪酸在细胞的生命活动中发挥着关键作用。
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