Figure 2

We show two reactions (R1, R2) sharing a common chemical compound, and both reactions contain more than one product (or substrate). The substrate graph G (chemical compounds) is shown dark blue circles. The reaction graph L _real (reactions) is shown with light red circles. If we apply a line graph transformation to this network, we would obtain more than two nodes in the transformed network. However, only two nodes (reactions) are present in the real process. These cases are computed and transformed by generating only as many nodes in the transformed network as reactions in the real metabolic process. We call this procedure physical line graph transformation.