Effect of odhA overexpression and odhA antisense RNA expression on Tween-40-triggered glutamate production by Corynebacterium glutamicum.

Recent studies have suggested that a decrease in the specific activity of the 2-oxoglutarate dehydrogenase complex (ODHC) is important for glutamate overproduction by Corynebacterium glutamicum. To further investigate the role of the odhA gene and its product in this process, we constructed the recombinant strains of C. glutamicum in which the expression of the odhA and its product could be controlled by odhA overexpression and odhA antisense RNA expression. We examined changes in glutamate production and ODHC specific activity of the constructed strains during glutamate production triggered by Tween 40 addition. The ODHC specific activity increased with odhA overexpression, resulting in dramatically reduced glutamate production despite Tween 40 addition, indicating that a decrease in the specific activity of ODHC is required for glutamate production induced by Tween 40 addition. However, odhA antisense RNA expression alone did not result in glutamate overproduction in spite of the decrease in ODHC specific activity. Rather, it enhanced glutamate production triggered by Tween 40 addition due to the additional decrease in ODHC specific activity, suggesting that odhA antisense RNA expression is effective in enhancing Tween-40-triggered glutamate overproduction. Our results suggest that a change in ODHC specific activity is critical but is not the only factor responsible for glutamate overproduction by C. glutamicum.