High-resolution ¹³C nuclear magnetic resonance studies of glucose metabolism in Escherichia coli

High-resolution ¹³C nuclear magnetic resonance spectra of suspensions of E. coli cells have been obtained at 90.5 MHz by using the Fourier transform mode. Anaerobic cells incubated with [1-¹³C]glucose show a time course of glycolysis in which the α and β glucose anomers disappear at different rates, lactate, succinate, acetate, alanine, and valine accumulate as end products of glycolysis, and fructose bisphosphate appears as an intermediate. It is shown that fructose bisphosphate is labeled at C-1 and C-6 during [1-¹³C]glucose catabolism. Upon oxygenation, glutamate appears with the ¹³C enrichment at the C-4, C-3, and C-2 positions, with the C-4 most intense. From the position of the ¹³C label it is concluded that valine is formed by condensation of pyruvate and that carbon enters the tricarboxylic acid cycle mainly through acetyl CoA.