毕赤酵母甲酸脱氢酶在大肠杆菌中的高表达及纯化

用PCR方法从毕赤酵母(Pichia pastoris)基因组DNA扩增甲酸脱氢酶(FDH)基因,通过定点突变密码子TAG(649-651位碱基)为GAG,突变后的基因片段插入表达载体pET-22b( )构建质粒pET-FDH,转化E．coli BL21(DE3)。基因工程菌在IPTG诱导下高效表达可溶性的FDH融合蛋白,蛋白的表达量占基因工程菌株总蛋白的30%。工程菌破壁上清液采用一步亲和层析分离,得到比活力为6．45U/mg的重组FDH。

Over-expression and Purification of Formate Dehydrogenase form Pichia pastoris in Escherichia coli

Formate dehydrogenase(FDH)coding gene was amplified from genomic DNA of Pichia pastoris by polymerase chain reaction, and the codon TAG(bases 649-651)was mutated to GAG using site-directed mutagenesis.The recombinant plasmid pET-FDH was con- structed by inserting the mutated DNA fragment into expression vector pET-22b(+),and transformed into E.coli BL21(DE3).FDH was expressed as a form of soluble prutein fused with 6×His tag at high level through IPTG induction.The amount of FDH was up to about 30% of the total cell protein. The cells-free crude extract was purified by one affinity chromatographic step,and resulting enzyme preparation revealed a specific activity of 6.45U/mg.