(A) Metabolite measurements in PANC-1 cells after culture for 48 hr in 0.05 mM glutamine. Quantification is normalized to 4 mM glutamine condition. Statistical significance was calculated by unpaired t-test. Mean ± SEM of five biological replicates is represented. (B) Overview of the GlcNAc salvage pathway feeding into the HBP. GlcNAc scavenged from O-GlcNAc removal or lysosomal breakdown of glycans can be phosphorylated by NAGK and used to regenerate UDP-GlcNAc. (C) Overview of the incorporation of 13C glucose into UDP-GlcNAc. Different parts of the molecule can be labeled from glucose-derived subunits; thus, isotopologs up to M+16 can be derived from glucose. (D) 13C glucose tracing into F-6-P, GlcNAc-P, and UDP-GlcNAc in indicated glutamine concentrations. % labeled GlcN indicates sum of M+6 and M+8 isotopologs for GlcNAc-P and sum of M+6, M+8, M+11, and M+13 for UDP-GlcNAc. % labeled Ribose indicates sum of M+5, M+7, M+11, and M+13 for UDP-GlcNAc. All isotopologs are graphed in Figure 2—figure supplement 1A. Statistical significance was calculated by unpaired t-test. Mean ± SEM of three biological replicates is represented. *p≤0.05; **p≤0.01; ***p≤0.001.