Multiple bond 13C-13C spin-spin coupling provides complementary information in a 13C NMR isotopomer analysis of glutamate

Most C-13 nuclear magnetic resonance (NMR) isotopomer analyses relate a metabolic index of interest to populations of C-13 isotopomers as reported by one-bond C-13-C-13 spin-spin couplings. Metabolic conditions that produce highly enriched citric acid cycle intermediates often lead to C-13 NMR spectra of metabolites such as glutamate that show extra multiplets due to long-range couplings. It can be demonstrated from C-13 NMR spectra of hearts perfused with mixtures of acetate plus propionate that multiplets in glutamate C2 arising from (3)J(25) coupling provide a direct readout of acetyl-CoA fractional enrichment (F-C1 and F-C3), while multiplets in glutamate C5 arising from (2)J(35) and 3J25 couplings quantitatively reflect enrichment of the anaplerotic substrate. Magn Reson Med 42:191-200, 1999. (C) 1999 Wiley-Liss, Inc.