Effect of adenine on metabolic fluxes in Escherichia coli DH5α and its acetate-tolerant mutant DA19

Abstract:

Abstract:［Objective］ In order to further understand the difference in metabolic regulation between Escherichia coli DH5α and its acetate-tolerant mutant DA19，we analyzed the effect of supplementing adenine in defined media on metabolic fluxes in the two strains． ［Methods］ E． coli DH5α and DA19 were continuously cultured in nitrogen-limited defined media without or with supplemented adenine． Based on mass balance and metabolic reaction stoichiometry，the metabolic fluxes in DH5α and DA19 at different culture condition were calculated，and the results were compared with the activities of key enzymes． ［Results］ The supplementation of adenine decreased specific glucose consumption rate and specific acetate production rate，and improved growth yield coefficient on glucose of DH5α． Nevertheless，specific pyruvate production rate did not significantly change． Furthermore acetate split ratio decreased whereas pyruvate and TCA split ratios increased． Obvious changes were observed in the activities of phosphofructokinase， 6-phosphoglucose dehydrogenase and acetokinase． Compared with DH5α，the supplementation of adenine increased rate specific pyruvate production rate of DA19 nearly 57% ，and other parameters did not change． In addition，it showed decreased TCA split ratio and greatly increased pyruvate split ratio，whereas no changes in the key enzyme activities were observed．The differences of enzyme activities in the two strains were reasonably consistent with those in metabolic fluxes． ［Conclusion］Because there were differences in the de novo biosynthesis capacity of purine nucleotides between DH5α and DA19，supplementation of adenine had completely different effect on metabolic fluxes in two strains．