葡萄糖异构酶基因工程菌的改造初探

葡萄糖异构酶（ｇｌｕｃｏｓｅｉｓｏｍｅｒａｓｅ，ＧＩ）是使用量最大的工业酶之一，可用于高果糖浆的生产，也可以用含木聚糖物质及废料为底物发酵生产乙醇，具有重要的经济价值．本文选择了表达载体ｐＢＶ２２０［１］，利用ＰＣＲ方法删除了原表达质粒ｐＴＫＤＧＩ１中ＧＩ结构基因５′端多余的核苷酸，并添加了合适的酶切位点，重新构建了能在大肠杆菌ＤＨ５α中高效表达ＧＩＧ１３８Ｐ的表达质粒ｐＢＺＧＩ１．传代实验表明，新表达体系的稳定性明显优于原表达体系．粗酶液经热处理、ＤＥＡＥＳｅｐｈａｒｏｓｅＦＦ和分子筛Ｓｅ…

Preliminary Study on Reformation of Engineered Bacteria E.coli of Glucose Isomerase

In order to realize stable overexpression of mutant glucose isomerase(GI)gene from Streptomyces diastaticus No.7 M1033 in E.coli, a 1.2 kb fragment containing the intact coding sequence of the protein was amplified specifically from plasmid pTKD GI1 by PCR.At the same time,45 bp unnecessary sequence at GI gene upstream was deleted.The amplified fragment was inserted into the expression vector pBV220 to obtain the recombinant plasmid pBZGI1,which was introduced into E.coli DH5α.Data gathered from passage of the generations of the strains showed that pBZGI1 in DH5α was much more stable than pTKD GI1 in K38/pGP1 2.Induced at 42℃,pBZGI1 overexpressed the mutant GI,which accounted for about 55% of total soluble proteins and was purified through heat treatment,DEAE Sepharose FF column and Sephacrcyl S 300 column.It also showed that the thermostability of the purified GI didn't decline though the undesired 15 amino acids present in N terminal was deleted.