Inverse metabolic engineering with phosphagen kinase systems improves the cellular energy state

Inverse metabolic engineering attempts to identify or construct desired phenotypes of applied interest to endow them on appropriate host organisms. A particular desirable phenotype is the ATP homeostasis exhibited by animal cells with high and variable ATP turnover through temporal and spatial energy buffering. This buffering is achieved by phosphagen kinase systems that consist of a specific kinase and its cognate phosphagen, which functions as a large pool of 'high-energy phosphates' that are used to replenish ATP during periods of high energetic demand. This review discusses recent advances and potentials of inverse metabolic engineering of cell types that do not normally contain such systems--bacteria, yeast, plants, and liver--with creatine or arginine kinase systems. Examples are discussed that illustrate how microbial metabolism can be tailored for large-scale industrial processes with imperfect mixing and how the liver can be protected from metabolic insults or stimulated for better regeneration.