瓦氏黄颡鱼(Pelteobagrus vachellii)脂肪酸去饱和酶FAD2和延伸酶ELOVL5的克隆及表达分析

MOLECULAR CLONING AND EXPRESSION OF FATTY ACID DESATURASE AND ELONGASE GENES IN DARKBARBEL CATFISH PELTEOBAGRUS VACHELLII

脂肪酸去饱和酶(FAD,fatty acyl desaturase)及延伸酶(ELOVL,elongases of very long chain fatty acids)在鱼类脂肪代谢过程中发挥了重要作用。利用RT-PCR克隆得到瓦氏黄颡鱼(Pelteobagrus vachellii)肝脏中控制高不饱和脂肪酸合成的(FAD2)和(ELOVL5)基因cDNA序列。瓦氏黄颡鱼FAD2cDNA片段长2041bp,编码447个氨基酸,含有3个组氨酸簇(HDx GH,Hxx HH,Qxx HH),含亚铁血红素结合基序(HPGG)的类似细胞色素b5结构域等。瓦氏黄颡鱼ELOVL5 cDNA片段长1065bp,编码294个氨基酸,含有组氨酸簇(Hxx HH)、内质网停留信号(K、R)和4个ELO共有的保守区域(Kxx Exx DT,Qxx FLHx YHH,Nxxx Hxx MYx YY,Txx Qxx Q)等结构域。荧光定量PCR分析表明,FAD2和ELOVL5 m RNA在瓦氏黄颡鱼脑、肝脏的表达量最高,显著高于肠道、脾脏、肾脏、鳃等组织。结果表明,瓦氏黄颡鱼具有合成高不饱和脂肪酸的关键酶FAD2和ELOVL5,且肝脏为合成高不饱和脂肪酸的主要场所。

Understanding the endogenous synthesis of long-chain polyunsaturated fatty acids is of benefit to fish feed formulation. A FADS2 and an ELOVL5 cDNA were cloned containing open reading frames（ORF） of 1338 base pair（bp） and 864 bp specifying proteins of 447 and 294 amino acids, respectively. The deduced amino acid sequence of Pelteobagrus vachellii FADS2 possessed conserved motif and included the histidine boxes, cytochrome b5 domain, transmembrane regions, and ELOVL 5 containing histidine boxes, endoplasmic reticulum retention signal domain, and transmembrane regions. In addition, FADS2 and ELOVL 5 m RNA distributed mainly in the brain and liver, and expressed significantly higher than that of intestine, spleen, kidney, gill, heart and muscle. These results indicate that P. vachellii possessed the desaturase and elongase, and the liver was the main tissues for synthesis of long-chain polyunsaturated fatty acids.