加强表达3-磷酸甘油醛脱氢酶对谷氨酸棒杆菌产L-丝氨酸的影响

Effects of glyceraldehyde-3-phosphate dehydrogenase overexpression on L-serine production in Corynebacterium glutamicum

在谷氨酸棒杆菌(Corynebacterium glutamicum)中,由3-磷酸甘油醛脱氢酶(glyceraldehyde-3-phosphate dehydrogenase,GAPDH)催化的反应是糖酵解途径的限速步骤,该反应还直接影响了L-丝氨酸的前体3-磷酸甘油酸的合成。研究首先比较了产L-丝氨酸的野生型菌株C.glutamicum SYPS-062与模式菌株C.glutamicum ATCC14067的GAPDH酶活力,发现SYPS-062的GAPDH酶活力比ATCC14067高了55.8%。进一步采用在C.glutamicum33a△SS基因组上增加gap A拷贝数的方法加强表达GAPDH,构建了重组菌C.glutamicum33a△SS-2gap A。重组菌GAPDH转录水平和酶活力分别提高119%和53%,最大比生长速率提高10.6%,总糖耗速率提高4.4%,L-丝氨酸产量提高17.4%,糖酸转化率提高12.2%,生产强度提高17.4%。结果表明,加强表达GAPDH能够提高重组菌的生长和糖耗速率,并能够提高L-丝氨酸的产量、糖酸转化率和生产强度。

In Corynebacterium glutamicum,the reaction catalyzed by glyceraldehyde-3-phosphate dehydrogenase（ GAPDH） is the rate-limiting step in the glycolysis pathway,also,it influences the biosynthesis of the L-serine precursor 3-phosphoglycerare directly. In this study,firstly,the GAPDH activity of the wild-type L-serine-producing strain C. glutamicum SYPS-062 and the model strain C. glutamicum ATCC14067 were compared. The GAPDH activity in SYPS-062 was 55. 8% higher than that in ATCC14067. Then,GAPDH was overexpressed by insertion of an additional gap A copy into genome of C. glutamicum 33 a △SS to construct the recombinant strain C. glutamicum33a△SS-2gap A. The transcriptional level and the enzyme activity of GAPDH in the recombinant strain were increased by119% and 53% respectively. The fermentation experiment showed that the maximum specific growth rate was increased by 10. 6%,the sugar consumption rate was increased by 4. 4%,the L-serine production was increased by17. 4%,the yield was increased by 12. 2%,and the productivity was increased by 17. 4% in the recombinant strain.These results demonstrated that overexpression of GAPDH could increase the growth and sugar consumption rate,and improve the production,yield and productivity of L-serine in the recombinant strain.