Highly connected hubs are common in a simulated network (top), as in natural networks (middle), but rare if group transfer reactions are excluded (bottom).
PFEIFFER
Metabolic networks rely heavily on a few crucial metabolic hubs, such as ATP, NADH, and glutamate, that are widely used in many cellular biochemical reactions. In contrast to hubs, most other metabolites each participate in only a few reactions. Now, research from Thomas Pfeiffer, Orkun Soyer, and Sebastian Bonhoeffer (ETH Zürich, Switzerland) shows that hubs are the natural byproduct of a widely accepted scenario of network evolution.The scenario, originally proposed by Kacser and Beeby, suggests that a few multifunctional enzymes evolved to create a large network of highly specialized enzymes. In the new work, the Swiss group ran computer simulations of this scenario using a small theoretical network initially consisting of 128 metabolites, one metabolite transporter, and seven catalytic enzymes....
