Enzyme-to-enzyme channeling in the early steps of glycolysis in rat pancreatic islets.

The enzyme-to-enzyme channeling of metabolic intermediates is not an uncommon process. The present review draws attention to recent experimental work documenting, in rat pancreatic islets, the enzyme-to-enzyme channeling of alpha-D-glucose 6-phosphate between hexokinase isoenzyme(s), mainly glucokinase, and phosphoglucoisomerase. Likewise, the possible enzyme-to-enzyme channeling of beta-D-fructose 6-phosphate between phosphoglucoisomerase and phosphofructokinase is briefly evoked. These considerations are relevant to the anomeric specificity of D-glucose metabolism, even in islets exposed to equilibrated D-glucose, to the perturbation of such an anomeric specificity in the phenomenon of so-called B-cell glucotoxicity, and to the correct interpretation of 3HOH generation from D-[2-(3H)]glucose.