Metabolism flows much like city traffic, according to an analysis by Eivind Almaas, Albert-László Barabási (University of Notre Dame, Notre Dame, IN), and colleagues. Although the vast majority of the reactions are less-traveled side roads, a few vital highways carry most of the metabolic traffic.
The organization of the numerous reactions that produces or consumes key metabolites is well-established in E. coli. Metabolites are arranged in a power–law distribution: a large number are made or consumed by only a few reactions, whereas a few metabolites are made or consumed by many more reactions. Barabási's group took a mathematical approach to examine the flux, or the frequency of use, through all of these reactions. Using flux–balance analysis, in which mass conservation, cellular equilibrium, and maximum growth rate constrain the possible flow through each reaction, the authors identified all possible flux states through every reaction for...
