Glucokinase activity in pancreatic islets was dose-dependently inactivated by D-glyceraldehyde, whereas islet hexokinase activity was not altered. In untreated islets, alpha-D-glucose stimulated insulin secretion more efficiently than beta-D-glucose at a glucose concentration of 10 mM. However, glyceraldehyde highly attenuated the insulin-secretory response of pancreatic islets to alpha-D-glucose compared with that to beta-D-glucose. Thus, there was apparently no anomeric preference of glucose-induced insulin secretion in glyceraldehyde-treated islets. Glyceraldehyde affected neither the alpha-preference of glucose phosphorylation by glucokinase nor the beta-preference of glucose phosphorylation by hexokinase. Our study suggests that defective discrimination of glucose anomers by glyceraldehyde-treated islets may be caused by inactivation of glucokinase.
Animals Enzyme Activation