ADDENDUM TO A NEW MATHEMATICAL APPROACH TO METABOLISM OF [14C]GLUCOSE: THE PYRUVATE CARBOXYLASE REACTION 1

Abstract —Previously published equations for analysis of [14C]glucose metabolism assumed that products of glycolysis enter the citric acid cycle only through acetyl‐CoA (Larrabee, 1978). These equations are now extended to include entrance into the citric acid cycle through the pyruvate carboxy‐lase reaction as well as via acetyl‐CoA and are applied to previously reported data from dorsal root ganglia of 15‐day‐old chicken embryos. The rate of output of labelled CO2 in the presence of [2‐14C] glucose could not be accounted for if the flux rate into the citric acid cycle through the pyruvate carboxylase reaction was assumed to be more than about 10–15% of that through acetyl‐CoA. It is concluded (1) that the pyruvate carboxylase reaction is a relatively minor source of material for the citric acid cycle in these ganglia and (2) that the previous conclusions about [14C]glucose metabolism, which ignored the pyruvate carboxylase reaction, need not be modified in the light of this reanalysis.