Fig. 8. Metabolism of [2-13C]pyruvate by fifth-instar M. sexta larvae, illustrating the derivation of 13C-enrichment in glycolytic and gluconeogenic intermediates, and in haemolymph trehalose. Principal metabolic derivations are shown with different symbols. Circles, 13C enrichments derived directly following carboxylation of the original 13C in [2-13C]pyruvate, as administered to larvae; *13C-enrichments derived from [2-13C]pyruvate, but following carboxylation and randomization at the fumarase-catalyzed step of the TCA cycle; 
13C-enrichments also derived from [2-13C]pyruvate following decarboxylation to acetyl-coenzyme A, condensation with oxaloacetate and subsequent synthesis of Glx. The metabolic effects of pentose cycling are not shown.
