Remote impact and local flux compensation. A system component can affect distant entities even greater than its closest neighbours, which is illustrated by TKb. Moreover, asymmetry in the criticalities of components can result in local flux compensation, which is illustrated by the alternative paths of TKb, TA and PGI. (A) An explicit demonstration of Figure 2A in the biological network overlay. It is organized as a metabolite network with TKb highlighted in blue and metabolites arranged along green circles representing distance levels. The amplitude is proportional to the color gradient (upper-right corner, "red-yellow" corresponds to "strong-slight"). (B) The enzyme-centric view of (A). Subfigure (A) and (B) mainly show the distributions of distances and amplitudes in a network's view, whereas the exact vertices' labels are not important here. To see the two pictures in high resolution, refer to Additional file 7 and 8. (C) Metabolites ribu5p, sed7p, rib5p and e4p in the pentose-phosphate pathway have increased fluxes after PGI knockout due to the asymmetry of system-levels properties of PGI, TKb and TA. The three enzymes mutually form alternative paths associating to the essential metabolite f6p.
Li and Liu BMC Systems Biology 2012 6(Suppl 1):S11 doi:10.1186/1752-0509-6-S1-S11