Is glucokinase responsible for the anomeric specificity of glycolysis in pancreatic islets?
At a low concentration of D-glucose (3.3 mM), the phosphorylation rate of this hexose in rat pancreatic islet homogenates incubated at 8 degrees C is higher with the beta- than with the alpha-anomer, as expected from the anomeric specificity of hexokinase. In the presence of a high concentration of glucose 6-phosphate (3.0 mM), which inhibits hexokinase but not glucokinase, the phosphorylation rates of the two anomers are not significantly different from one another. Nevertheless, in intact islets exposed at 8 degrees C to the same low concentration of D-glucose, the alpha-anomer augments, more than the beta-anomer, the production of lactic acid and net uptake of 45Ca. At the same concentration (3.3 mM), the alpha-anomer is also more potent than the beta-anomer in enhancing insulin release from perfused pancreases stimulated at 37 degrees C by L-leucine or by the combination of Ba2+ and theophylline. It is concluded that the participation of glucokinase is not essential for the anomeric specificity of glycolysis and insulin release in rat pancreatic islets.
D000818:Animals; D002118:Calcium / Q000378:metabolism; D005941:Glucokinase / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism* / Q000494:pharmacology; D019298:Glucose-6-Phosphate; D005958:Glucosephosphates / Q000494:pharmacology; D006019:Glycolysis; D006593:Hexokinase / Q000037:antagonists & inhibitors; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D007773:Lactates / Q000096:biosynthesis; D019344:Lactic Acid; D010766:Phosphorylation; D051381:Rats; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
D005958:Glucosephosphates; D007328:Insulin; D007773:Lactates; D019344:Lactic Acid; D019298:Glucose-6-Phosphate; D006593:Hexokinase; D005941:Glucokinase; D005947:Glucose; D002118:Calcium