Metabolism of D-Glucose Anomers in Rat Pancreatic Islets Exposed to Equilibrated D-Glucose

Abstract

This study aims at establishing the contribution of α- and β-D-glucose to the total generation of ³HOH by rat pancreatic islets exposed to D-[2 - ³H]glucose or D-[5 - ³H] glucose at anomeric equilibrium. The islets were incubated for 60 min at 4 °C in the presence of equilibrated D-glucose (2.8 and 8.3 mM) mixed with tracer amounts of either α- or β-D-glucose labelled with tritium on either the C₂ or C₅ of the hexose. Relative to their respective concentrations, ³HOH generation from the anomers labelled with tritium on the C₂ or C₅ of the hexose provided β/α ratios comparable to those previously found at both 2.8 and 8.3mM, when the islets were exposed to each anomer separately. The relative contributions of each anomer to the total generation of ³HOH was also close to the theoretical values derived from mathematical models for the catabolism of D-glucose at anomeric equilibrium in rat islets at both 2.8 and 8.3 mM and in the case of both D-[2 - ³H]glucose and D-[5 - ³H]glucose. Thus, even in islets exposed to D-glucose at anomeric equilibrium, the metabolic fate of α-D-glucose differs vastly from that of β-D-glucose, the enzyme-to-enzyme channelling between hexokinase isoenzymes, especially glucokinase, and phosphoglucoisomerase being restricted to α-D-glucose 6-phosphate.

Key words

Rat pancreatic islets - Metabolism of D-glucose anomers - Enzyme-to-enzyme channelling of glycolytic intermediates

References

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