Uniform sampling of steady-state flux spaces: means to design experiments and to interpret enzymopathies.

TitleUniform sampling of steady-state flux spaces: means to design experiments and to interpret enzymopathies.
Publication TypeJournal Article
Year of Publication2004
AuthorsPrice ND, Schellenberger J, Palsson BØ
JournalBiophysical journal
PubMed Date2004 Oct
KeywordsAnimals, Blood Proteins, Computer Simulation, Erythrocytes, Gene Expression Regulation, Enzymologic, Humans, Metabolism, Inborn Errors, Models, Biological, Models, Statistical, Multienzyme Complexes, Sample Size, Signal Transduction

Reconstruction of genome-scale metabolic networks is now possible using multiple different data types. Constraint-based modeling is an approach to interrogate capabilities of reconstructed networks by constraining possible cellular behavior through the imposition of physicochemical laws. As a result, a steady-state flux space is defined that contains all possible functional states of the network. Uniform random sampling of the steady-state flux space allows for the unbiased appraisal of its contents. Monte Carlo sampling of the steady-state flux space of the reconstructed human red blood cell metabolic network under simulated physiologic conditions yielded the following key results: 1), probability distributions for the values of individual metabolic fluxes showed a wide variety of shapes that could not have been inferred without computation; 2), pairwise correlation coefficients were calculated between all fluxes, determining the level of independence between the measurement of any two fluxes, and identifying highly correlated reaction sets; and 3), the network-wide effects of the change in one (or a few) variables (i.e., a simulated enzymopathy or fixing a flux range based on measurements) were computed. Mathematical models provide the most compact and informative representation of a hypothesis of how a cell works. Thus, understanding model predictions clearly is vital to driving forward the iterative model-building procedure that is at the heart of systems biology. Taken together, the Monte Carlo sampling procedure provides a broadening of the constraint-based approach by allowing for the unbiased and detailed assessment of the impact of the applied physicochemical constraints on a reconstructed network.

Alternate JournalBiophys. J.
PubMed ID15454420



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