Figure 4.

Time courses for labeling of glutamate, lactate, and fatty acyl resonances during perfusion with medium containing [1,6-¹³C₂] glucose and unlabeled glutamine. (A) Time course fits for labeling of glutamate (indicated with “fit” ending) at positions 4, 3, and 2. Glu4, ¹³C at glutamate-C4; Glu4s, singlet at glutamate-C4; Glu4d34, doublet at glutamate-C4. Glu2, 13C enrichment at glutamate-C2; Glu3, 13C at glutamate-C3. “fit” ending stands for the model fit and no-ending reflects experimental values. (B) Time courses for labeling glutamate at positions 2 and 3. Fitted curves labeled with ending “fit” are Glu2 and Glu3 total; Glu2s, singlet at glutamate-2; Glu3s, singlet at glutamate-3; Glu3d, doublet at glutamate-3. PE stands for positional enrichment – this is predicted mitochondrial enrichment of acetyl-CoA at position C2 and mitochondrial Pyr at position C3 multiplied by factor 10. Curves are fit, and points are experimental data. (C,D) Experimental data and least-squares fit of time course for labeling of lactate-C3 and fatty acyl methylene (–(CH₂)_n–) resonance in proliferating DB-1 melanoma cells. (C) Time course for labeling of total lactate-C3 (medium + intracellular). (D) De novo lipogenesis in melanoma cells. Time course for labeling of fatty acyl methylene (–(CH₂)_n–) resonance. [This research was originally published in Journal of Biological Chemistry. Shestov et al. (14). © the American Society for Biochemistry and Molecular Biology.]