[Revealing key interactions in the metabolic network: a model of primary phosphate transport in bacteria]

One of the main problems of metabolic engineering is to determine the genetically controlled limiting links of a metabolic network. We have built a model of the primary transport of inorganic phosphates (Pi), analyzed the Pi metabolic network in Gram-negative bacteria, and determined the factors controlling the phosphate exchange. The model explains why the Pi primary transport is not observed at the release stage. The nonlinearity of primary transport and the differences in its parameters in the membrane and within the cell give rise to transport asymmetry, i.e., the Pi release rate is low as compared with the uptake rate, and is small at the background of secondary transport. Discussed is a general scheme of coordination between primary and secondary transport, which are interconnected through the substrate-product reration.