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Metabolic loss of deuterium from isotopically labeled glucose
Author(s) -
BenYoseph Oded,
Kingsley Peter B.,
Ross Brian D.
Publication year - 1994
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910320317
Subject(s) - chemistry , pentose phosphate pathway , biochemistry , metabolism , deuterium , carbohydrate metabolism , glucose uptake , isotopic labeling , glycolysis , metabolic pathway , insulin , biology , endocrinology , organic chemistry , physics , quantum mechanics
The isotopically substituted molecule (6‐ 13 C, 1, 6, 6‐ 2 H 3 )glucose was evaluated to determine whether metabolic 2 H loss would prevent its use in quantitating pentose phosphate pathway (PPP) activity. PPP activity causes the C1 of glucose to be lost as CO 2 , while C6 can appear in lactate. 2 H NMR analysis of the lactate produced from this glucose can distinguish (3‐ 2 H)‐lactate (from C1 of glucose) from (3‐ 13 C, 3, 3‐ 2 H Z )lactate (from C6 of glucose). 2 H NMR spectroscopic analysis of medium containing (4‐ 13 C, 1,6,6 −2 H 3 ) glucose after incubation with cultured rat 9L glioma cells suggested a 30.8 ± 2.1% PPP activity as compared with 6.0 ± 0.8% from separate, parallel incubations with (1‐ 13 C)glucose and (6‐ 13 C)glucose. Subsequent experiments with other isotopically labeled glucose molecules suggest that this discrepancy is due to selective loss of 2 H from the C1 position of glucose, catalyzed by phosphoman‐nose isomerase. Failure to consider 2 H exchange from the C1 and C6 positions of glucose can lead to incorrect conclusions in metabolic studies utilizing this and other deuterated or tritiated glucose molecules.