Study on the metabolism of Escherichia coli DH5alpha and its acetate-tolerant mutant DA19 based on key enzyme activity analysis / 生物工程学报

ABSTRACT

The differences in metabolism in Escherichia coli DH5alpha and its acetate-tolerant mutant DA19 were analyzed based on the activity of key enzymes involved in central metabolism when both strains were continuously cultured in nitrogen source-limited defined media. The activity of glucose-6-phosphate dehydrogenase (G6PDH) and isocitrate dehydrogenase (ICDH) in DA19 increased as compared with those in DH5alpha, while acetate kinase (ACK) and phosphofructosekinase (PFK) decreased. These indicated that more carbon flux of DA19 entered the phosphopentose pathway (PPP) and less entered the glycolytic (EMP) pathway and acetic acid production (Ack-Pta) pathway. Therefore, the differences in activity of key enzyme coincided with increased cell yield based on consumed glucose (Y(X/G)) and decreased production of acetic acid and pyruvate of DA19. G6PDH and ICDH in DH5alpha were up-regulated by addition of adenine, while ACK and PFK were down-regulated. On the other hand, adenine had little effect on those in DA19. The enzymes except PFK in both strains were down-regulated by sodium acetate, especially the activity of ICDH in DH5alpha. These results suggested changed flux of central metabolic pathways were also consistent with the changes of growth properties and byproducts formation.