Direct Estimation of Metabolic Flux by Heavy Isotope Labeling Simultaneous with Pathway Inhibition: Metabolic Flux Inhibition Assay

  • Tong Zhang
  • Christiaan F. Labuschagne
  • Karen H. Vousden
  • Oliver D. K. MaddocksEmail author
Part of the Methods in Molecular Biology book series (MIMB, volume 1862)


Heavy isotope labeled metabolites are readily detected by mass spectrometry and are commonly used to analyze the rates of metabolic reactions in cultured cells. The ability to detect labeled metabolites—and infer fluxes—is influenced by a number of factors that can confound simplistic comparative assays. The accumulation of labeled metabolites is strongly influenced by the pool size of the metabolite of interest and also by changes in downstream reactions, which are not always fully perceived. Here, we describe a method that overcomes some of these limitations and allows simple calculation of reaction rates under low nutrient, rapid reaction rate conditions. Acutely increasing the pool of the metabolite of interest (by adding a pulse of excess unlabeled nutrient to the cells) rapidly increases accumulation of labeled metabolite, facilitating a more accurate assessment of reaction rate.

Key words

Metabolic flux inhibition assay Carbon-13 Heavy isotope metabolic tracer Pathway activity Pulse-stop-flux 



ODKM and ACN are funded by Cancer Research UK Career Development Fellowship C53309/A19702. KHV and CFL are funded by CRUK Grant C596/A10419.


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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  • Tong Zhang
    • 1
  • Christiaan F. Labuschagne
    • 2
  • Karen H. Vousden
    • 2
  • Oliver D. K. Maddocks
    • 1
    Email author
  1. 1.Wolfson Wohl Cancer Research Centre, Institute of Cancer SciencesUniversity of GlasgowGlasgowUK
  2. 2.The Francis Crick InstituteLondonUK

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