Metabolic Regulation of the Main Metabolism

It is quite important to understand the overall regulation mechanism of a cell system for the proper modeling. Namely, it is desirable to incorporate how the cell detect environmental signals, integrate such information, and how the cell system is regulated. In particular, carbon catabolite regulation (CCR) is of primal importance for the analysis of overflow metabolism and for the selective assimilation of multiple carbon sources. Metabolic regulation is made by enzyme level regulation and transcriptional regulation via the transcription factors. The effects of feed-forward and feed-back regulations on the metabolism is also explained based on the simple linear system. For CCR, proper understanding on the phosphotransferase system (PTS) and the transcriptional regulation by cAMP-Crp and Cra is important. The coordinated regulation between catabolic and anabolic (nitrogen source-assimilation) metabolism may be made by the keto acid such as αKG. The effect of oxygen level on the metabolism is explained in terms of global regulators such as ArcA/B and Fnr. Moreover, the nitrogen regulation in response to nitrogen limitation is explained. The modeling may be made by taking into account the metabolic regulation mechanisms of the central metabolism.

Keywords: Metabolic regulation, catabolite regulation, nitrogen regulation, transcription factors, Cra, cAMP-Crp, acetate overflow, catabolite repression, multiple carbon sources, ArcA, Fnr, feed-forward regulation, feed-back regulation, nitrogen regulation.