Metabolic loss of deuterium from isotopically labeled glucose.
The isotopically substituted molecule (6-13C, 1, 6, 6-2H3)glucose was evaluated to determine whether metabolic 2H loss would prevent its use in quantitating pentose phosphate pathway (PPP) activity. PPP activity causes the C1 of glucose to be lost as CO2, while C6 can appear in lactate. 2H NMR analysis of the lactate produced from this glucose can distinguish (3-2H)-lactate (from C1 of glucose) from (3-13C, 3, 3-2H2)lactate (from C6 of glucose). 2H NMR spectroscopic analysis of medium containing (6-13C, 1, 6, 6-2H3)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 (1-13C)glucose and (6-13C)glucose. Subsequent experiments with other isotopically labeled glucose molecules suggest that this discrepancy is due to selective loss of 2H from the C1 position of glucose, catalyzed by phosphomannose isomerase. Failure to consider 2H 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.
Ben-Yoseph
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Department of Radiology, School of Medicine, University of Michigan Medical Center, Ann Arbor.
Kingsley
P B
PB
Ross
B D
BD
D000818:Animals; D001932:Brain Neoplasms / Q000201:enzymology / Q000378:metabolism*; D002247:Carbon Isotopes; D002540:Cerebral Cortex / Q000201:enzymology / Q000378:metabolism; D003903:Deuterium / Q000737:chemistry / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D005910:Glioma / Q000201:enzymology / Q000378:metabolism*; D005947:Glucose / Q000737:chemistry / Q000378:metabolism*; D006019:Glycolysis; D007773:Lactates / Q000737:chemistry / Q000378:metabolism*; D019344:Lactic Acid; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008359:Mannose-6-Phosphate Isomerase / Q000378:metabolism; D008956:Models, Chemical; D010427:Pentose Phosphate Pathway; D011770:Pyruvate Kinase / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D014407:Tumor Cells, Cultured
D002247:Carbon Isotopes; D007773:Lactates; D019344:Lactic Acid; D003903:Deuterium; D011770:Pyruvate Kinase; D008359:Mannose-6-Phosphate Isomerase; D005947:Glucose