三角褐指藻△^5-脂肪酸脱氢酶基因的克隆及在酿酒酵母中的表达

Cloning and expression in Saccharomyces cerevisiae of △^5-fatty acid desaturase gene from Phaeodactylum tricornutum

△5-脂肪酸脱氢酶是合成花生四烯酸的关键酶。根据已报道的△5-脂肪酸脱氢酶基因设计引物,分别从三角褐指藻基因组DNA和总cDNA中扩增得到1520 bp和1410 bp的特异片段,序列分析结果显示,结构基因中含有一个大小为110 bp的内含子,这是国内外首次报道。将△5-脂肪酸脱氢酶基因亚克隆到大肠杆菌和酿酒酵母的穿梭表达载体pYES2.0中,在大肠杆菌中筛选到含有目的片段的重组质粒pYPTD5,用电击转化的方法将重组质粒pYPTD5转化到营养缺陷型酿酒酵母菌株INVSc1中,在缺省培养基中筛选得到酿酒酵母转化菌株YPTD5。在合适的培养条件下,添加外源底物双高γ-亚麻酸和诱导物半乳糖,培养并收集菌体。通过脂肪酸甲酯气相色谱分析,表明三角褐指藻△5-脂肪酸脱氢酶基因在酿酒酵母中获得了高效的表达,将双高γ-亚麻酸转化为花生四烯酸,其底物转化率达到了45.9%。

△^5-fatty acid desaturase is the key enzyme in synthesis of arachidonic acid. Two specific fragment was cloned from genomic DNA and total cDNA of Phaeodactylum tricornutum through PCR with primer designed according to the reported sequences, respectively 1520 bp and 1410 bp. Comparison of the genomic and cDNA sequences revealed that the △^5-fatty Acid Desaturase gene from genomic DNA had an 110 bp intron. The 1.4 kb was subcloned into the yeast-E, coli shuttle vector pYES2.0, then an expression recombinant plasmid pYPTD5 contatining target gene was constructed. The plasmid pYPTD5 was transformed into defective mutant INCScl of Saccharomyces cerevisiae for expression by electrotransformation method. Dihomo-γ-linolenic acid was provided as an exogenous substrate to the yeast cultures, with galactose as inducer. By GC detecting, the recombinant S. cerecisiae had arachidonic acid. The results indicated that high level expression of △^5-fatty acid desaturase, and the substrate conversion reached 45.9%.