PHOSPHOGLUCOISOMERASE-CATALYZED INTERCONVERSION OF HEXOSE PHOSPHATES - A MODEL FOR D-[2-H-3]GLUCOSE METABOLISM IN HUMAN ERYTHROCYTES

When d-[2-3H]glucose 6-phosphate mixed with the unlabeled ester is converted to d-[1-3H]fructose 6-phosphate and 3HOH in the phosphoglucoisomerase reaction and then to d-[1-3H]fructose 1,6-bisphosphate in the phosphofructokinase reaction, the specific radioactivity of the latter metabolite and the production of 3HOH relative to the total generation of tritiated end products are both inversely related to the concentration of phosphofructokinase. In human erythrocytes, the modeling of d-[2-3H]glucose metabolism, based on the activity of phosphoglucoisomerase in cell homogenates and on the steady-state content of d-glucose 6-phosphate and d-fructose 6-phosphate in intact cells, indicates that the back-and-forth interconversion of these esters is about five-times higher than the net glycolytic flux. Yet, the production of 3HOH from d-[2-3H]glucose is about 20% lower than the net glycolytic flux, as judged from the production of 3HOH from d-[5-3H]glucose. Thus, an incomplete detriation of d-[2-3H]glucose is not incompatible with an extensive interconversion of hexose 6-phosphates in the reaction catalyzed by phosphoglucoisomerase. © 1991.