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. 1990 Nov 15;272(1):127–132. doi: 10.1042/bj2720127

Evaluation of the pentose phosphate pathway from 14CO2 data. Fallibility of a classic equation when applied to non-homogeneous tissues.

M G Larrabee 1
PMCID: PMC1149666  PMID: 2124803

Abstract

A classic equation that has frequently been used to estimate the fraction of glucose metabolized by the pentose phosphate pathway, using 14CO2 data, is more simply re-derived with careful consideration of the assumptions involved and the conditions under which it is applicable. The equation is shown to be unreliable for non-homogeneous tissues, depending on the fraction of triose phosphate converted to CO2. The formula in question is as follows: ([1]CO2/G-[6]CO2/G)/(1-[6]CO2/G) = 3Fmet./(1 + 2Fmet.) where [1]CO2 and [6]CO2 are output rates of carbons 1 and 6 of glucose respectively to CO2, G is the rate of glucose uptake and Fmet. is the fraction of the glucose that is metabolized to CO2 and triose phosphate by the pentose phosphate pathway, allowing for recycling of an appropriate fraction of the fructose-6-phosphate produced by the pathway. This analysis illustrates the importance of suitably testing any equation that assumes homogeneity before application to non-homogeneous tissues.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Bauer U., Brand K. Carbon balance studies of glucose metabolism in rat cerebral cortical synaptosomes. J Neurochem. 1982 Jul;39(1):239–243. doi: 10.1111/j.1471-4159.1982.tb04725.x. [DOI] [PubMed] [Google Scholar]
  2. Borowitz M. J., Stein R. B., Blum J. J. Quantitative analysis of the change of metabolite fluxes along the pentose phosphate and glycolytic pathways in Tetrahymena in response to carbohydrates. J Biol Chem. 1977 Mar 10;252(5):1589–1605. [PubMed] [Google Scholar]
  3. Giroix M. H., Sener A., Malaisse W. J. Pentose cycle pathway in normal and tumoral islet cells. FEBS Lett. 1985 Jun 3;185(1):1–3. doi: 10.1016/0014-5793(85)80728-6. [DOI] [PubMed] [Google Scholar]
  4. Hothersall J. S., Baquer N., Greenbaum A. L., McLean P. Alternative pathways of glucose utilization in brain. Changes in the pattern of glucose utilization in brain during development and the effect of phenazine methosulfate on the integration of metabolic routes. Arch Biochem Biophys. 1979 Dec;198(2):478–492. doi: 10.1016/0003-9861(79)90522-8. [DOI] [PubMed] [Google Scholar]
  5. KATZ J., WOOD H. G. The use of C14O2 yields from glucose-1- and -6-C14 for the evaluation of the pathways of glucose metabolism. J Biol Chem. 1963 Feb;238:517–523. [PubMed] [Google Scholar]
  6. KATZ J., WOOD H. G. The use of C14O2 yields from glucose-1- and -6-C14 for the evaluation of the pathways of glucose metabolism. J Biol Chem. 1963 Feb;238:517–523. [PubMed] [Google Scholar]
  7. Kuehn A., Scholz R. Rates of flux through the pentose cycle in perfused rat liver. A procedure for the calculation of rates of substrate flux from 14CO2 production from [1-14C]glucose. Eur J Biochem. 1982 Jun;124(3):611–617. doi: 10.1111/j.1432-1033.1982.tb06638.x. [DOI] [PubMed] [Google Scholar]
  8. Larrabee M. G. The pentose cycle (hexose monophosphate shunt). Rigorous evaluation of limits to the flux from glucose using 14CO2 data, with applications to peripheral ganglia of chicken embryos. J Biol Chem. 1989 Sep 25;264(27):15875–15879. [PubMed] [Google Scholar]
  9. Laychock S. G. Prostaglandin E2 and alpha 2 adrenoceptor agonists inhibit the pentose phosphate shunt in pancreatic islets. Arch Biochem Biophys. 1989 Feb 15;269(1):354–358. doi: 10.1016/0003-9861(89)90117-3. [DOI] [PubMed] [Google Scholar]
  10. Magnusson I., Chandramouli V., Schumann W. C., Kumaran K., Wahren J., Landau B. R. Pentose pathway in human liver. Proc Natl Acad Sci U S A. 1988 Jul;85(13):4682–4685. doi: 10.1073/pnas.85.13.4682. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Malaisse W. J., Giroix M. H., Sener A. Anomeric specificity of glucose metabolism in the pentose cycle. J Biol Chem. 1985 Nov 25;260(27):14630–14632. [PubMed] [Google Scholar]
  12. O'Fallon J. V., Wright R. W., Jr Quantitative determination of the pentose phosphate pathway in preimplantation mouse embryos. Biol Reprod. 1986 Feb;34(1):58–64. doi: 10.1095/biolreprod34.1.58. [DOI] [PubMed] [Google Scholar]
  13. Verspohl E. J., Breuning I., Ammon H. P. Effect of CCK-8 on pentose phosphate shunt activity, pyridine nucleotides, and glucokinase of rat islets. Am J Physiol. 1989 Jan;256(1 Pt 1):E68–E73. doi: 10.1152/ajpendo.1989.256.1.E68. [DOI] [PubMed] [Google Scholar]
  14. WOOD H. G., KATZ J., LANDAU B. R. ESTIMATION OF PATHWAYS OF CARBOHYDRATE METABOLISM. Biochem Z. 1963;338:809–847. [PubMed] [Google Scholar]
  15. WOOD H. G., KATZ J., LANDAU B. R. ESTIMATION OF PATHWAYS OF CARBOHYDRATE METABOLISM. Biochem Z. 1963;338:809–847. [PubMed] [Google Scholar]
  16. Williams J. F., Arora K. K., Longenecker J. P. The pentose pathway: a random harvest. Impediments which oppose acceptance of the classical (F-type) pentose cycle for liver, some neoplasms and photosynthetic tissue. The case for the L-type pentose pathway. Int J Biochem. 1987;19(9):749–817. doi: 10.1016/0020-711x(87)90239-4. [DOI] [PubMed] [Google Scholar]
  17. Williams J. F., Blackmore P. F., Clark M. G. New reaction sequences for the non-oxidative pentose phosphate pathway. Biochem J. 1978 Oct 15;176(1):257–282. doi: 10.1042/bj1760257. [DOI] [PMC free article] [PubMed] [Google Scholar]

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