Localized enzymes form a tree-like loop-dense network A matrix representing the connectivity of the 1214 different biochemical reactions of E.coli was constructed (see Additional file 1: Figure S1B). A. Left Diagram illustrating the clustering (cls) and within-group connectivity (wgc) of localized (green) and non-localized (blue) enzymes. Red edges represent inter-group connections. Dotted arrows represent pathways 1 & 2 connected via localized reactions. Right Diagram illustrates the distribution of randomly selected nodes constructed to compare mean loop density with nodes from localized enzymes. B. Left. Associated p-values of the KS-test for higher number of loops in nodes derived from localized enzymes compared to non- localized ones. Right. Four plots showing the Log-scale distributions of the number of loops for each node in localized (green) and non-localized (blue) enzymes. The type of loop is indicated top right. C. Table shows the associated p-values for higher number of loops per connection in nodes derived from localized enzymes compared to nodes chosen randomly.