Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.1.1 (hexokinase)
 5,274 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have developed radiometric assays for small quantities of glycerol, glucose and glycogen, based on a technique described by Thorner and Paulus (1971, J. Biol. Chem. 246, 3885-3894) for the measurement of glycerokinase activity. In the glycerol assay, glycerol is phosphorylated with [32P]ATP and glycerokinase, residual [32P]ATP is hydrolyzed by heating in acid, and free [32P]phosphate is removed by precipitation with ammonium molybdate and triethylamine. Standard dose-response curves were linear from 50 to 3000 pmol glycerol with less than 3% SD in triplicate measurements. Of the substances tested for interference, only dihydroxyacetone gave a slight false positive signal at high concentration. When used to measure glycerol concentrations in serum and in media from incubated adipose tissue, the radiometric glycerol assay correlated well with a commonly used spectrophotometric assay. The radiometric glucose assay is similar to the glycerol assay, except that glucokinase is used instead of glycerokinase. Dose response was linear from 5 to 3000 pmol glucose with less than 3% SD in triplicate measurements. Glucosamine and N-acetylglucosamine gave false positive signals when equimolar to glucose. When glucose concentrations in serum were measured, the radiometric glucose assay agreed well with hexokinase/glucose-6-phosphate dehydrogenase (H/GDH)-based and glucose oxidase/H2O2-based glucose assays. The radiometric method for glycogen measurement incorporates previously described isolation and digestion techniques, followed by the radiometric assay of free glucose. When used to measure glycogen in mouse epididymal fat pads, the radiometric glycogen assay correlated well with the H/GDH-based glycogen assay. All three radiometric assays offer several practical advantages over spectral assays.
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PMID:Radiometric assays for glycerol, glucose, and glycogen. 281 33

Our previous studies on cultured rabbit lens epithelial cells from 4-day-old rabbits showed that the glutathione redox cycle plays an important role in detoxifying H2O2, a potentially damaging oxidant present in the aqueous humor. Here we report the effect of donor age and cell density on the ability of cultured rabbit lens epithelial cells to detoxify H2O2. Lens epithelial cells (8 x 10(5] from a 4-day-old and an 8-year-old rabbit were cultured for 3 hr in minimal essential medium (MEM) or in MEM containing 0.01-0.1 mM H2O2 maintained with glucose oxidase. We determined the effect of H2O2 on the level of reduced glutathione (GSH), hexose monophosphate shunt activity, cell growth, and morphology. For growth studies, cells were exposed to the desired concentration of H2O2 for 3 hr and then cultured in MEM plus 10% rabbit serum for 7 days and counted. Young and old untreated cells contained high levels (30-40 nmol/8 x 10(5) cells) of GSH. Cells from 4-day-old rabbits tolerated 0.03 mM H2O2 with no effect on GSH and a minimal decrease in subsequent cell growth. However, in the older cells, GSH and growth were substantially diminished following treatment with 0.03 mM H2O2. Cells plated out at high density (8 x 10(5] were more tolerant of 0.03 mM H2O2 than cells plated out at low density (5 x 10(4]. Maximum shunt activity in the younger cells exposed to H2O2 was twice that of the older cells and occurred at a higher level of H2O2 (0.04 compared with 0.03 mM). Enzyme activities in untreated young and old cells were comparable for hexokinase, glucose-6-phosphate dehydrogenase, and glutathione peroxidase. However, glutathione reductase activity was 50% lower in the cells from the 8-year-old rabbit. The toxicity of H2O2 to cultured lens epithelial cells was directly related to donor age and inversely related to cell density. The damage in the older lens epithelial cells at 0.03 mM H2O2 was apparently due, in part, to a diminished response of the glutathione redox cycle to oxidative challenge.
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PMID:Influence of the activity of glutathione reductase on the response of cultured lens epithelial cells from young and old rabbits to hydrogen peroxide. 335 66

The kinetic behaviour of a heterogeneous branched bienzyme system of beta-D-glucose oxidase and hexokinase on glucose has been studied. In this sequence, hexokinase is inhibited by its product glucose 6-phosphate and also by D-gluconic acid produced from the parallel enzymic reaction of glucose oxidase. Effect of glucose concentrations on the product's distribution in branched pathway of the bienzyme system is dependent on the kinetic properties of hexokinase and glucose oxidase. Product inhibitions, which are also pH dependent, have a strong regulatory role on the reaction flux.
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PMID:Kinetic regulation of hexokinase activity in a heterogeneous branched bienzyme system. 335 35

Methods for 2-deoxyglucose (2-DG) and 2-deoxyglucose 6-phosphate (DG6P) are described which are based on the fact that DG6P is oxidized by glucose-6-phosphate dehydrogenase (G6PDH), but at a rate 1000-fold slower than for glucose 6-phosphate, whereas hexokinase phosphorylates 2DG and glucose at comparable rates. Therefore, by adding the two enzymes in a suitable order, and in appropriate concentrations, 2DG, glucose, DG6P, and glucose 6-P can all be separately measured. To avoid a side reaction from the use of a high level of G6PDH, when measuring DG6P, glucose is first removed with glucose oxidase plus aldose reductase.
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PMID:Enzymatic assays for 2-deoxyglucose and 2-deoxyglucose 6-phosphate. 355 57

We evaluated whether any monosaccharides inhibit glycolysis in erythrocytes and discovered that D-mannose does. In the presence of D-mannose, glucose can be accurately measured by either the hexokinase procedure or the glucose oxidase procedure. In comparison studies with other glucose preservatives, we found that after 2 h at room temperature glucose decreased by 21 (SD 13) mg/L in D-mannose-treated blood, 93 (SD 10) mg/L in sodium fluoride-treated blood, 28 (SD 21) mg/L in ice-cooled blood, and 144 (SD 28) mg/L in control blood (no preservative treatment). Because D-mannose acted in the early phase of glycolysis, it was a more effective preservative than sodium fluoride; moreover, its use did not preclude measurement of sodium and potassium in the blood samples. D-Mannose did not interfere with other routine chemical tests except for the assay of creatine kinase involving coupled enzymes hexokinase/glucose-6-phosphate dehydrogenase. Creatine kinase could be correctly assayed in the presence of D-mannose by using glucokinase instead of hexokinase. D-Mannose can be used with or without anticoagulant and is compatible with most types of multi-channel automated analyzers.
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PMID:D-mannose as a preservative of glucose in blood samples. 200 64

Hexokinase methods for serum glucose assay appeared to give slightly but consistently higher inter-laboratory coefficients of variation than all methods combined in the UK External Quality Assessment Scheme; their performance over a two-year period was therefore compared with that for three groups of glucose oxidase methods. This assessment showed no intrinsic inferiority in the hexokinase method. The greater variation may be due to the more heterogeneous group of instruments, particularly discrete analysers, on which the method is used. The Beckman Glucose Analyzer and Astra group (using a glucose oxidase method) showed the least inter-laboratory variability but also the lowest mean value. No comment is offered on the absolute accuracy of any of the methods.
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PMID:An examination of the hexokinase method for serum glucose assay using external quality assessment data. 376 57

The glucometer II system is a small measurement device with built-in batch-specific pressbutton calibration. The corresponding test strip "Glucostix" uses a two-color system. The blood glucose test strip can be evaluated both visually and by instrument. The precision determined in series was between 2.0% and 6.7% using control sera. The day-to-day precision was between 1.5% and 7.9%. Comparison of the methods on the basis of 781 and 109 capillary blood samples respectively revealed a good agreement between the hexokinase method or the glucose oxidase method (Beckman analyser) and the glucometer II values. The precision of measurement by the system was comparable in the two test strip batches employed. Visual reading of the test strips revealed a good agreement with the laboratory method in the hypoglycemic and normoglycemic range; at higher concentrations of blood glucose, a trend to underestimation of the measurement values was shown. The easy handling and small size of the instrument facilitates measurement of blood glucose by the patient under everyday conditions.
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PMID:[Clinical testing of a new blood glucose measuring system. A cooperative study at 8 centers]. 382 20

Results for urinary glucose by the Boehringer Mannheim BM33071 test pad and a hexokinase-based method agree well. The new test, which involves the glucose oxidase/peroxidase reaction, measures as little as 260 mg of glucose per liter. Acetoacetate, beta-hydroxybutyrate, and human hemoglobin do not interfere.
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PMID:New test for urinary glucose (BM33071) evaluated. 396 21

A study of the reverse reaction of rat brain hexokinase (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1) has been performed using a photometric method based on a mutarotase-glucose oxidase-peroxidase-chromogen system to trap and visualize glucose, plus a glycerol kinase-glycerol system to trap ATP. Glucose 6-phosphate or 2-deoxyglucose 6-phosphate were used as phosphoryl donors at different concentrations of ADP. Variation of glucose 6-phosphate concentrations resulted in a biphasic curve from which apparent Km and Ki values of ca. 0.2 mM were calculated. In contrast, variation of 2-deoxyglucose 6-phosphate concentrations resulted in Michaelian kinetics with an apparent Km of 2 mM. The Km value for MgADP was 16 mM irrespective of the nature and concentration of the hexose 6-phosphate substrate. These results are fully consistent with an allosteric site for glucose 6-phosphate as an explanation for the inhibition of animal hexokinases by glucose 6-P and further indicate that the maximal rate is the parameter affected. From these observations and previous knowledge, the possible occurrence in animal hexokinases of a regulatory site for ATP to account for the competition between glucose 6-phosphate and ATP in the forward reaction is postulated.
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PMID:Allosteric inhibition of brain hexokinase by glucose 6-phosphate in the reverse reaction. 400 67

Van Etten, James L. (University of Illinois, Urbana), H. Peter Molitoris, and David Gottlieb. Changes in fungi with age. II. Respiration and respiratory enzymes of Rhizoctonia solani and Sclerotium bataticola. J. Bacteriol. 91:169-175. 1966.-The rate of respiration of Rhizoctonia solani and Sclerotium bataticola decreased with age. This decrease in respiratory rate might be produced by a decrease in the specific activity of one or more enzymes involved in carbohydrate metabolism. Specific activities in cell-free extracts were measured for most of the enzymes in the hexose monophosphate shunt, Embden-Meyerhof-Parnas pathway, tricarboxylic acid cycle, and terminal electron-transport system. In addition, glucose oxidase, isocitritase, and malic enzyme were measured. In R. solani, increases in activity with age occurred for hexokinase, alpha-glycerolphosphate dehydrogenase, malic dehydrogenase, and cytochrome oxidase. Decreases occurred for phosphohexokinase, aconitase, nicotinamide adenine dinucleotide-specific isocitric dehydrogenase, reduced nicotinamide adenine dinucleotide oxidase, and at least one of the enzymes between 3-phosphoglycerate and pyruvate. In S. bataticola, increases in activity with age were observed for phosphohexokinase, pyruvic dehydrogenase, fumarase, malic dehydrogenase, and malic enzyme, whereas none of the enzymes decreased. The specific activities of the remaining enzymes did not change with age in either fungus.
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PMID:Changes in fungi with age. II. Respiration and respiratory enzymes of Rhizoctonia solani and Sclerotium bataticola. 428 29


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