The large-scale organization of metabolic networks

In a cell or microorganism, the processes that generate mass, energy, infor mation transfer and cell-fate specification are seamlessly integrated throu gh a complex network of cellular constituents and reactions(1). However, de spite the key role of these networks in sustaining cellular functions, thei r large-scale structure is essentially unknown. Here we present a systemati c comparative mathematical analysis of the metabolic networks of 43 organis ms representing all three domains of life. We show that, despite significan t variation in their individual constituents and pathways, these metabolic networks have the same topological scaling properties and show striking sim ilarities to the inherent organization of complex non-biological systems(2) . This may indicate that metabolic organization is not only identical for a ll living organisms, but also complies with the design principles of robust and error-tolerant scale-free networks(2-5), and may represent a common bl ueprint for the large-scale organization of interactions among all cellular constituents.