Glucose 1,6-Diphosphate Formation by Phosphoglucomutase in Mammalian Tissues

Abstract

Glucose 1,6-diphosphate concentrations in 10 mouse tissues were found to range from 70 to 80 µmoles per kg in brain and red blood cells to 7 to 10 µmoles per kg in testes and pancreas. There was no discernible correlation between levels of glucose 1,6-diphosphate and levels of glucose 6-phosphate, uridine diphosphoglucose or phosphoglucomutase, or Michaelis constants of phosphoglucomutase for its coenzyme. Ischemia caused a rapid decrease in glucose 1,6-diphosphate level in brain, whereas there was little or no effect of starvation on the level in liver, or of maximal electrical stimulation on the level in muscle. Evidence is presented to show that glucose 1,6-di-P in muscle can be synthesized by P-glucomutase itself from fructose-1,6-di-P and glucose-6-P (or glucose-1-P). The rate of synthesis is only about 0.015% of the mutase rate for glucose-1-P, but this would be sufficient to synthesize the glucose-1,6-di-P in mouse muscle in 3 min. The equilibrium constant is about 12 for (fructose-1,6-di-P) (glucose-6-P):(fructose-6-P) (glucose-1,6-di-P).