title: Metabolic networks and their evolution.
abstract: Since the last decade of the twentieth century, systems biology has gained the ability to study the structure and function of genome-scale metabolic networks. These are systems of hundreds to thousands of chemical reactions that sustain life. Most of these reactions are catalyzed by enzymes which are encoded by genes. A metabolic network extracts chemical elements and energy from the environment, and converts them into forms that the organism can use. The function of a whole metabolic network constrains evolutionary changes in its parts. I will discuss here three classes of such changes, and how they are constrained by the function of the whole. These are the accumulation of amino acid changes in enzyme-coding genes, duplication of enzyme-coding genes, and changes in the regulation of enzymes. Conversely, evolutionary change in network parts can alter the function of the whole network. I will discuss here two such changes, namely the elimination of reactions from a metabolic network through loss of function mutations in enzyme-coding genes, and the addition of metabolic reactions, for example through mechanisms such as horizontal gene transfer. Reaction addition also provides a window into the evolution of metabolic innovations, the ability of a metabolism to sustain life on new sources of energy and of chemical elements.
authors: Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland. andreas.wagner@ieu.uzh.ch
authors: Andreas
authors: A
authors: Wagner
mesh_terms: D000818:Animals; D001419:Bacteria; D005057:Eukaryotic Cells / Q000201:enzymology*; D019143:Evolution, Molecular; D005658:Fungi; D020440:Gene Duplication; D022761:Gene Transfer, Horizontal; D007700:Kinetics; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D055432:Metabolomics; D008954:Models, Biological; D011387:Prokaryotic Cells / Q000201:enzymology*; D049490:Systems Biology