Alpha- and beta-anomeric preference of glucose-induced insulin secretion at physiological and higher glucose concentrations, respectively.

We determined the anomeric preference of glucose phosphorylation by islet glucokinase, glucose utilization by pancreatic islets, and insulin secretion induced by glucose over a wide range of glucose concentrations. alpha-D-Glucose was phosphorylated faster than beta-D-glucose by islet glucokinase at lower glucose concentrations (5 and 10 mM), whereas the opposite anomeric preference was observed at higher glucose concentrations (40 and 60 mM). At 20 mM, there was no significant difference in phosphorylation rate between the two anomers. Similar patterns of anomeric preference were observed both in islet glucose utilization and in glucose-induced insulin secretion. The present study affords strong evidence that glucokinase is responsible for the anomeric preference of glucose-stimulated insulin secretion through anomeric discrimination in islet glucose utilization.