氨基脱氧分支酸合成酶对Corynebacterium glutamicum SYPS-062积累L-丝氨酸的影响

Effect of ADC Synthase to the L-serine Accumulation by C.glutamicum SYPS-062

为阐明氨基脱氧分支酸合成酶(ADC合成酶)在Corynebacterium glutamicum SYPS-062体内积累L-丝氨酸过程中的作用,通过交叉PCR以及同源重组的方法敲除叶酸途径关键酶ADC合成酶的编码基因pabAB,构建了叶酸缺陷型菌株Corynebacterium glutamicum SYPS-062△pabAB,同时构建pabAB基因增强表达重组菌C.glutamicum SYPS-062(pJC I-pabAB)。分别考察了ADC合成酶对菌株生长的影响、对L-丝氨酸降解途径关键酶丝氨酸羟甲基转移酶(SHMT)的影响以及其对L-丝氨酸积累的影响。结果表明,与出发菌株相比,增强表达基因pabAB重组菌的ADC合成酶的酶活力提高了33%,SHMT酶的酶活力提高了30%,其最大比生长速率(μ_m)提高了48%,单位细胞产酸率(Yp/x)降低了36.2%;而敲除基因pabAB重组菌的ADC合成酶的酶活力降低了61%。SHMT酶的酶活力降低了20%,最大比生长速率降低了32%,单位细胞产酸率提高了12%。

To study the roles ADC synthase played in the process of L-serine accumulation in C. glutamicum SYPS-062, the pab- AB mutant was successfully constructed through crossover PCR and homologous recombination, and the pabAB overexpression mutant was also construted. The effect of ADC synthase to the growth of the three strain, the activity of SHMT and the L-serine accumulation were studied. The results showed that the ADC synthase raised 33% with the overexpression of gene pabAB ,while it decreased 61% after the gene pabAB was deleted. Meanwhile the SHMT activity of C. glutamicum SYPS-062 （pJCI-pabAB）increased 30%, the μm raised 48% ,and the Yp/x decreased 36. 2% compared with that of the original srtain C. glutamicum SYPS-062 ;The SHMT activity of C. glutamicum SYPS-062 A pabAB decresaed 20% compared to that of the original strain, the μm decreased 32% , while the Yp/x increased 12% compared with the original strain.