Metabolic loss of deuterium from isotopically labeled glucose

✍ Scribed by Oded Ben-Yoseph; Peter B. Kingsley; Brian D. Ross

• Book ID: 102956601
• Publisher: John Wiley and Sons
• Year: 1994
• Tongue: English
• Weight: 524 KB
• Volume: 32
• Category: Article
• ISSN: 0740-3194
• DOI: 10.1002/mrm.1910320317

✦ Synopsis

Abstract

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.