title: Determination of metabolic flux ratios from 13C-experiments and gas chromatography-mass spectrometry data: protocol and principles.
abstract: Network topology is a necessary fundament to understand function and properties of microbial reaction networks. A valuable method for experimental elucidation of metabolic network topology is metabolic flux ratio analysis, which quantifies the relative contribution of two or more converging pathways to a given metabolite. It is based on 13C-labeling experiments, gas chromatography-mass spectrometry analysis, and probabilistic equations that relate mass distributions in proteinogenic amino acids to pathway activity. Here, we describe the protocol for sample generation and illustrate the principles underlying the calculation of metabolic flux ratios with three examples. These principles are also implemented in the publicly available software FiatFlux, which directly calculates flux ratios from the mass spectra of amino acids.
authors.affiliation: Institute for Molecular Systems Biology, ETH Zürich, Switzerland.
authors.forename: Annik
authors.initials: A
authors.lastname: Nanchen
authors.forename: Tobias
authors.initials: T
authors.lastname: Fuhrer
authors.forename: Uwe
authors.initials: U
authors.lastname: Sauer
mesh_terms: D000596:Amino Acids / Q000032:analysis / Q000378:metabolism*; D001412:Bacillus subtilis / Q000254:growth & development / Q000378:metabolism*; D002247:Carbon Isotopes / Q000378:metabolism*; D004926:Escherichia coli / Q000254:growth & development / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D005947:Glucose / Q000378:metabolism; D053858:Metabolic Networks and Pathways; D012694:Serine / Q000032:analysis / Q000378:metabolism; D012984:Software
chemical_list: D000596:Amino Acids; D002247:Carbon Isotopes; D012694:Serine; D005947:Glucose