Structural analysis of a core model for carbohydrate uptake in Escherichia coli

The analysis of biochemical reaction schemes is often limited by uncertainties in the kinetic parameters. Here, we apply Metabolic Control Analysis to explore structurally determined properties of a feed-forward loop in carbohydrate uptake and glycolysis in Escherichia coli. This part of the metabolic network is a starting point for a sensory system and therefore an important element for the understanding of the coordination between metabolism and signal transduction. By analytical calculations for various model structures of increasing complexity, we explore for which kinetic reaction rates and in which parameter ranges the resulting core models offer the decaying degree of phosphorylation that is observed in experiments. In particular, the consequences of allowing reversibility will be described and the role of the feed-forward enzymatic activation will be discussed. Finally, it is shown that the proposed model can be used as a generic basis for an extended and more realistic version of the network.