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Quantitation of Fluxes in the Gluconeogenic, Glycolytic, and Pentose Phosphate Pathways in Isolated Rat Hepatocytes: Energetic Considerations

  • Jacob J. Blum
  • Michael S. Rabkin
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 194)

Abstract

For any given substrate mixture and hormonal state, a large number of factors serve to regulate the flow of metabolites along the major pathways of carbohydrate metabolism in hepatocytes. In addition to the amounts of enzymes present, these factors include the intracellular levels of various effectors such as fructose 2,6-bisphosphate, ADP, ATP, and alanine, among others, and the phosphorylation states of several key enzymes. Enzyme levels are subject to long term regulation by dietary and hormonal influences, while effector levels and the phosphorylation state of regulatory enzymes are subject to moment-to-moment changes in hormonal states. While studies on purified enzymes or on tissue homogenates have contributed enormously to our present understanding of the many factors that help regulate metabolic fluxes, a more complete understanding of in vivo regulation of intermediary metabolism requires studies on perfused liver or, in so far as they can be considered as representative of the intact liver, on isolated hepatocytes.

Keywords

Pentose Phosphate Pathway Triose Phosphate Isomerase Triose Phosphate Substrate Mixture Futile Cycle 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. Blum, J.J., and Stein, R.B., 1982, On the analysis of metabolic networks, in:Biological Regulation and Development,Vol. 3A, R.F. Goldberger and K.R. Yamamoto, eds., Plenum Press, New York.Google Scholar
  2. Brand, I.A., and Soling, H.D., 1982, Metabolite-controlled phosphorylation of phosphofructokinase in rat hepatocytes, Eur. J. Biochem., 122: 175.Google Scholar
  3. Crawford, J.M., and Blum, J.J., 1982, On the use of trace levels of [1–14C]galactose to estimate cycling between pentose 6-phosphate and fructose diphosphate, Arch. Biochem. Biophys., 216: 42.Google Scholar
  4. Crawford, J.M., and Blum, J.J., 1983, Quantitative analysis of flux along the gluconeogenic, glycolytic and pentose phosphate pathways under reducing conditions in hepatocytes isolated from fed rats, Biochem.J., 212: 585.PubMedGoogle Scholar
  5. Foe, L.G., and Kemp, R.G., 1982, Properties of phospho and dephospho forms of muscle phosphofructokinase, J. Biol. Chem., 257: 6368.Google Scholar
  6. Hers, H.G., and Van Schaftingen, E., 1982, Fructose 2,6 bisphosphate two years after its discovery, Biochem. J., 206: 1.Google Scholar
  7. Hue, L., 1981, The role of futile cycles in the regulation of carbohydrate metabolism in the liver, Adv. Enzymol., 52: 247.Google Scholar
  8. Hue, L., 1982, Futile cycles and regulation of metabolism, in: “Metabolic Compartmentation,” H. Sies, ed., Academic Press, New York.Google Scholar
  9. Katz, J., and Rognstad, R., 1976, Futile cycles in the metabolism of glucose, Curr. Top. Cell. Regul., 10: 237.Google Scholar
  10. Pilkis, S.J., Walderhaug, M., Murray, K., Beth, A., Venkataramu, S.D., Pilkis, J., and El-Maghrabi, M.R., 1983, 6-Phosphofructo-2-kinase/fructose 2,6-bisphosphate from rat liver - isolation and identification of a phosphorylated intermediate, J. Biol. Chem., 258: 6135.Google Scholar
  11. Sommercorn, J., and Freedland, R.A., 1982, Regulation of hepatic phosphofructokinase by 6-phosphogluconate, J. Biol. Chem., 257: 9424.Google Scholar
  12. Stein, R.B., and Blum, J.J., 1978, On the analysis of futile cycles in metabolism, J. Theor. Biol., 72: 487.Google Scholar

Copyright information

© Plenum Press, New York 1986

Authors and Affiliations

  • Jacob J. Blum
    • 1
  • Michael S. Rabkin
    • 1
  1. 1.Department of PhysiologyDuke University Medical CenterDurhamUSA

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