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In both starved and diazoxide-treated rats, the rate of D-(U-14C)glucose phosphorylation (10 mM) by liver cytosol, as measured in the presence of D-glucose 6-phosphate, was lower than in fed control rats. Moreover, in these two models of insulinopenia, the sensitivity of glucokinase to a lowering of temperature from 30 degrees C to 10 degrees C and its(More)
The kinetic behaviour of liver glucokinase was examined in the liver cytosol from normal and streptozotocin diabetic rats. In addition to the classical reduction in glucokinase activity, diabetes severely lowered both the energy of activation and the apparent affinity of the enzyme for D-glucose. Diabetes also impaired the positive cooperativity found at(More)
Incubation of yeast phosphoglucoisomerase for 14 days at a high concentration (100 mM) of D-glucose was found to cause the non-enzymatic glycation of the enzyme. The kinetic properties of the glycated and control enzymes were similar in terms of specific activity, affinity for D-glucose 6-phosphate, isotopic discrimination between D-(U-14C) glucose(More)
1. Cross-linked and permeabilized rat erythrocytes were incubated for 2-5 min at 37 degrees C in the presence of ATP and either D-[U-14C]glucose 6-phosphate (3 mM) mixed with unlabelled D-fructose 6-phosphate (1 mM) or D-[U-14C]fructose 6-phosphate (1 mM) mixed with unlabelled D-glucose 6-phosphate (3 mM). 2. The contribution of molecules derived from the(More)
In the liver postmicrosomal supernatant of starved rats, the high-Km glucose-phosphorylating enzymic activity, presumably attributable to glucokinase, is not solely decreased but also displays an apparently lower affinity and less pronounced temperature dependency than in fed rats. In the presence of exogenous D-glucose 6-phosphate and D-fructose(More)
The kinetics of the low-Km hexokinase isoenzymes, which obey the Michaelis-Menten equation, can be established from the Km (Michaelis constant) and Vmax (maximal velocity) values for either equilibrated D-glucose or its alpha- and beta-anomers. In the case of the high-Km glucokinase isoenzyme, however, the sigmoidal substrate dependency and the competition(More)
In rat liver slices incubated in the absence of exogenous D-glucose, both the basal and glucagon-stimulated output of D-glucose resulted in the production of a greater relative amount of alpha-D-glucose than that found at anomeric equilibrium. Comparable results were obtained in isolated hepatocytes. In these experiments, the rate of glycogenolysis largely(More)
In rat pancreatic islets, hypoxia severely decreased both the oxidation of D-[U-14C]glucose and the release of insulin evoked by D-glucose. The production of [14C]lactate was increased in the hypoxic islets, the relative magnitude of such an increment being greater at low (2.8 mM) than high (8.3 and 16.7 mM) D-glucose concentrations. Hypoxia increased the(More)
Aldolase and triose phosphate isomerase both display strict specificity towards the enantiomers of [1-3H]glycerone 3-phosphate. The enantiomer generated from D-[1-3H]glyceraldehyde 3-phosphate produces 3HOH in the aldolase reaction, whilst the other enantiomer generated from D-[3-3H]fructose 1,6-bisphosphate is solely detritiated in the reaction catalyzed(More)
Adult rats injected with streptozotocin during the neonatal period displayed in the fed state moderate hyperglycemia. However, the percentages of glycated hemoglobin in erythrocytes and glycated lactate dehydrogenase in liver and pancreatic islets, as well as the sorbitol and glycogen content of the islets, were not significantly increased. Likewise, in(More)