Redesign of allosteric regulation of enzyme for self-regulated dynamic control of metabolic fluxes in microbial amino acid production

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The goal of this project is to redesign allosteric regulation of enzyme(s) for self-regulated and dynamic metabolic control in bioproduction processes. Using homoserine dehydrogenase (HSD) and lysine biosynthesis as a model system, we will implement lysine as a signalling molecule to control metabolic flux to the threonine pathway which is necessary for cell growth but undesired for lysine production. Different HSD variants with modified allosteric regulation will be designed. By construction of Corynebacterium glutamicum mutants bearing the mutated HSD, we will use metabolic and flux analyses to investigate the flux redistribution upon the genetic perturbation. With our approach, the enzyme activity of HSD should be adjusted according to the cellular physiological conditions during the bioprocess, especially to lysine concentration. At the stage of cell growth, the intracellular lysine concentration is low, and thus the inhibition of HSD will not be strong, allowing enough flux to the threonine pathways for cell growth. With the increase of lysine concentration in the production phase, the inhibition of HSD will be automatically enhanced and thus the substrate will be channelled into the pathway of lysine production. With this novel approach, we will develop a new tool for overcoming some of the major problems associated with drastic genetic modifications like gene overexpression or knockout in conventional strain development.