Asymmetrical Labeling ofd-Glucose Generated from [3-13C]Pyruvate in Rat Hepatocytes

The generation of¹³C-labeledd-glucose isotopomers by rat hepatocytes incubated for 30 or 120 min in the presence of 10 mm[3-¹³C]pyruvate was assessed by¹³C NMR. The amount of C₁-labeledd-glucose exceeded that of C₂-labeled hexose, which was itself higher than that of C₃-labeledd-glucose. A comparable hierarchy was observed in the C₆–C₅–C₄moiety of the hexose. The latter moiety ofd-glucose was more efficiently labeled, however, than the C₃–C₂–C₁moiety. This finding is similar to that both previously reported and again observed in the present study when hepatocytes were exposed to [2-¹³C]pyruvate. These converging observations thus support the concept of enzyme-to-enzyme channeling ofd-glyceraldehyde 3-phosphate between glyceraldehyde-3-phosphate dehydrogenase and phosphofructoaldolase.