Two-dimensional, rotational-echo double-resonance NMR of cell culture metabolism.

Two-dimensional, rotational-echo double-resonance 13C NMR, a new solid-state NMR technique, has been used to show that the relative fluxes of the labeled chemical bond of L-[2-13C,15N]serine along four metabolic pathways (direct purine synthesis, direct glycine incorporation into protein, direct non-glycyl incorporation into protein, and nitrogen scrambling with loss of carbon) are 1:2:6:36, respectively, for Klebsiella pneumoniae under conditions of nitrogenase derepression. These determinations were performed on a single sample of lyophilized, double-labeled, intact cells. Analysis of the homogeneity of the distribution of label suggests that the primary role of serine in shortening derepression is in providing specific carbon and nitrogen for RNA synthesis.