ABSTRACT
Themetabolic network of an organism consists of spontaneous and enzyme-catalyzed reactions that transform smallmolecules, ormetabolites, into others to produce energy and building blocks for essential macromolecules. Large-scale metabolic networks have been reconstructed from genome sequence and literature data for a number of organisms, including Escherichia coli, yeast, and humans [1-3]. These networks shed light on the metabolic capabilities of these organisms and their differences. Now with the ability to identify metabolic networks from sequence data and the vast accumulated knowledge ofmetabolism,we are challenged to characterize how these networks
function. A metabolic pathway defines the static sequence of feasible and observable biochemical reaction steps involved in the conversion of inputs into this pathway into a product.Metabolic fluxes are the rates at whichmaterial is processed through the steps of a pathway. Flux distributions indicate patterns of network utilization. The complete analysis of how a cell functions will include not only a description of its metabolic network, but also an understanding of flux distribution in different environments.
