Invariant features of metabolic networks: a data analysis application on scaling properties of biochemical pathways

The network metaphor is currently one ofthe most common general paradigms in biological sciences: this paradigm spans di3erent scales ofde4nition going f rom gene regulation to protein–protein interaction studies and metabolic regulation networks. Generally, the networks are de4ned by the nature ofthe connected elements (nodes) and their relative relations (edges). In this paper we demonstrate how the same biochemical regulation network can assume di3erent shapes in terms ofboth constituting elements and intervening relations while remaining recognizable as a speci4c entity. This behaviour can be explained by the general scaling properties ofbiological networks and points to regulation pathways as emergent features of biochemical systems posited at a di3erent hierarchical level with respect to the intervening metabolites. c