Deciphering the crucial roles of AraC-type transcriptional regulator Cgl2680 on NADPH metabolism and L-lysine production in Corynebacterium glutamicum.

Lysine is widely used in food, medical and feed industries. The biosynthesis of L-lysine is closely related to NADPH level, but the regulation mechanism between the biosynthesis of L-lysine in C. glutamicum and the cofactor NADPH is still not clear. Here, a high intracellular NADPH level strain C. glutamicum XQ-5Δpgi::(zwf-gnd) was constructed by blocking the glycolytic pathway and overexpressing the pentose phosphate pathway in the lysine-producing strain C. glutamicum XQ-5, and the intracellular NADPH level in strain XQ-5Δpgi::(zwf-gnd) was increased from 3.57 × 10-5 nmol/(104 cells) to 1.8 × 10-4 nmol/(104 cell). Transcriptome analyses pointed to Cgl2680 as an important regulator of NADPH levels and L-lysine biosynthesis in C. glutamicum. By knocking out the gene Cgl2680, the intracellular NADPH level of the recombinant C. glutamicum lysCfbr ΔCgl2680 was raised from 7.95 × 10-5 nmol/(104 cells) to 2.04 × 10-4 nmol/(104 cells), consequently leading to a 2.3-fold increase in the NADPH/NADP+ ratio. These results indicated that the regulator Cgl2680 showed the negative regulation for NADPH regeneration. In addition, Cgl2680-deficient strain C. glutamicum lysCfbr ΔCgl2680 showed the increase of yield of both L-lysine and L-leucine as well as the increase of H2O2 tolerance. Collectively, our data demonstrated that Cgl2680 plays an important role in negatively regulating NADPH regeneration, and these results provides new insights for breeding L-lysine or L-leucine high-yielding strain.