Metabolic network analysis. A powerful tool in metabolic engineering.

Metabolic network analysis is a tool for investigating the features that identify the topology of a metabolic network and the relative activities of its individual branches. The pillars of metabolic network analysis are mathematical modeling, allowing for a quantitative analysis, biochemical knowledge of, for example, reaction stoichiometry, and the experimental techniques, providing input for the modeling part. The modeling part includes metabolite balancing, usually the basis for metabolic flux analysis, and isotope balancing. Isotope balancing can be used for both identification of active pathways and for estimation of the relative fluxes through two pathways leading to the same metabolite, aspects that are difficult to investigate using metabolite balancing. The combination of metabolite and isotope balancing is very powerful and constitutes the basis of metabolic network analysis. With the main focus being on investigating the metabolic network structure, this review describes how central metabolic features, for example, pathway identification, flux distribution, and compartmentation, can be addressed using a combination of metabolite balancing and labeling experiments.