Systems level engineering of Corynebacterium glutamicum - Reprogramming translational efficiency for superior production

In this study, we replaced the natural start codons of different enzymes in the central carbon metabolism of Corynebacterium glutamicum to influence their activity toward improved production of the feed amino acid lysine. It was found that the translational start codon directly affects the intracellular activity of the encoded enzyme, whereby the common ATG generally led to higher values as compared with the rare variant GTG. This could be exploited to specifically amplify or attenuate enzyme activities in order to redirect carbon flux from undesired, competing pathways toward reactions supporting lysine formation. Replacement of the natural ATG codon by GTG reduced the specific enzyme activity of pyruvate dehydrogenase (PDH) and phosphoglucoisomerase by 60 and 40%, respectively. Vice versa, the activity of glucose 6-phosphate dehydrogenase was increased by 40% by the substitution GTG- > ATG. Implementation of the attenuated pyruvate dehydrogenase in the background of lysine producing C. glutamicum increased product yield by 17%. This was related to a redirection of the metabolic flux toward the supply of the lysine precursor oxaloacetate. The amplified expression of glucose 6-phosphate dehydrogenase by the start codon exchange increased lysine yield by 10%, linked to an increased flux toward NADPH supply in the pentose phosphate pathway.