The Arabidopsis enzyme-enzyme metabolic network. (A) The interaction between two enzymes. Dots represent enzymes, directional edges represent metabolite flux. (B) Diagram showing in-degree, out-degree and bottlenecks. The in-degree of node α is 5 whereas its out-degree is 1, node α and node β are bottlenecks. The between-ness shown on the top left of each nodes. (C) The enzyme-enzyme network and the distribution of 173 WGD-enzymes. Dots represent enzymes and the lines represent the interactions among enzymes. Dots highlighted by red represent the WGD-enzymes. (D) Cartography of Arabidopsis metabolic network. The circles represent modules (1 to 11) and the lines reflect the connections among modules. The area of color in each module is proportional to the number of enzymes that belong to the corresponding functional pathways. The blanks represent the enzymes whose corresponding pathways are not represented in the module.