Controlling the carbon flux between glycolysis and the pentose phosphate pathway via targeted protein degradation in Corynebacterium glutamicum.

Controlling the carbon flux is important for efficient production of value-added chemicals using microbial cell factories. In this study, we developed a system to control the carbon flux in Corynebacterium glutamicum via targeted protein degradation. We employed an SspB-dependent protein degradation system targeting the SsrA tag and applied it to control the carbon flux. First, we selected a degradation tag efficiently recognized by the ClpXP protease in C. glutamicum using green fluorescent protein (GFP) as a model protein. Among the four tags examined in this study, a mutant SsrA tag with DAS residues from Escherichia coli resulted in specific GFP degradation only when the adaptor SspB was induced in C. glutamicum. Next, we applied this system to control the carbon flux. We selected phosphoglucoisomerase (PGI) encoded by pgi, as a target protein, to control the carbon flux between glycolysis and pentose phosphate pathway (PPP) and 1,5-diaminopentane as a model product to evaluate this control system. Compared with the parental strain, the specific growth rate of the engineered strain decreased by 36 %, whereas the yield and production rate of 1,5-diaminopentane increased by 193 % and 70 %, respectively. This is the first report on the application of a protein degradation system to control carbon flux in C. glutamicum. The system developed in this study can be widely applied for designing C. glutamicum cell factories for efficient production of varied value-added chemicals.