Estimation of metabolic fluxes, expression levels and metabolite dynamics of a secondary metabolic pathway in potato using label pulse-feeding experiments combined with kinetic network modelling and simulation.
Understandig of the function of complex metabolic networks and methods for their rational design, e.g. for the overproduction of metabolites or for the abatement of metabolically related diseases, are still in its infancy compared to their real complexity. Using the increasing knowledge about genome sequences and its bioinformatic exploration, whole genome network analysis and design is increasingly possible, presently primarily using stoichiometric information. In a next higher level kinetic information that cannot be derived from genome analysis is used to describe also the dynamics of network. This allows a much more detailed understanding and application for design, as has been shown for the production of citric acid . We will briefly describe the state-of-the-art and present and likely future developments. Using stoichiometric information, methods like elementary mode analysis permit direct genome scale studies providing, e.g. valuable information about potential maximal yields of overproduction also using mixed substrates. They also provide a certain guidance for the design of potentially useful mutants, e.g. by deletion of genes promoting by-product formation. We have applied this technique to analyze methionine production in C. glutamicum and E. coli . On essentially the same basis genome wide metabolic flux analysis is possible delivering in vivo activities of a network at specific conditions. Combining flux balancing with, e.g. C-labelling techniques, a detailed picture can be routinely achieved for many bacterial systems and applied for designing mutants . This requires, however, the combination of well defined cultivation, sampling, (bio)chemical analysis, modeling and parameter estimation techniques. Steady-