Figure 2.

Metabolism of [U-¹³C]glutamine in GDH KO synaptosomes. Synaptosomes were isolated from control (white) and GDH KO mice (black) and incubated with [U-¹³C]glutamine. The synaptosomal extracts were analyzed for amino acid contents by HPLC and for percentage ¹³C labelling by GC-MS (a, c, e, f). The labelling patterns derived from [U-¹³C]glutamine (M + 5) after conversion to glutamate M + 5 and subsequent entrance into the TCA cycle by direct (b) and after first turn TCA cycle (d) metabolism that corresponds to the data shown in (c) and (e), respectively. Direct metabolism of [U-¹³C]glutamine (M + 5) leads to formation of citrate M + 4 (b), which can be further metabolism during the first turn of the TCA cycle (d). The legend in (f) applies to all panels. Asp, aspartate; cit: citrate; fum, fumarate; gln, glutamine; glu, glutamate; mal, malate; suc, succinate; α-kg, α-ketoglutarate. (n = 4–7 independently prepared synaptosomes per condition.)