Reprogramming One-Carbon Metabolic Pathways To Decouple l‑Serine Catabolism from Cell Growth in Corynebacterium glutamicum

• Published in: ACS synthetic biology 2018-02, Vol.7 (2), p.635-646
• Main Authors: Zhang, Yun, Shang, Xiuling, Lai, Shujuan, Zhang, Yu, Hu, Qitiao, Chai, Xin, Wang, Bo, Liu, Shuwen, Wen, Tingyi
• Format: Article
• Language: English
• ISSN: 2161-5063; 2161-5063
• DOI: 10.1021/acssynbio.7b00373

l-Serine, the principal one-carbon source for DNA biosynthesis, is difficult for microorganisms to accumulate due to the coupling of l-serine catabolism and microbial growth. Here, we reprogrammed the one-carbon unit metabolic pathways in Corynebacterium glutamicum to decouple l-serine catabolism from cell growth. In silico model-based simulation showed a negative influence on glyA-encoding serine hydroxymethyltransferase flux with l-serine productivity. Attenuation of glyA transcription resulted in increased l-serine accumulation, and a decrease in purine pools, poor growth and longer cell shapes. The gcvTHP-encoded glycine cleavage (Gcv) system from Escherichia coli was introduced into C. glutamicum, allowing glycine-derived 13CH2 to be assimilated into intracellular purine synthesis, which resulted in an increased amount of one-carbon units. Gcv introduction not only restored cell viability and morphology but also increased l-serine accumulation. Moreover, comparative proteomic analysis indicated that abundance changes of the enzymes involved in one-carbon unit cycles might be responsible for maintaining one-carbon unit homeostasis. Reprogramming of the one-carbon metabolic pathways allowed cells to reach a comparable growth rate to accumulate 13.21 g/L l-serine by fed-batch fermentation in minimal medium. This novel strategy provides new insights into the regulation of cellular properties and essential metabolite accumulation by introducing an extrinsic pathway.