Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

The pathways for catabolism of fructose were investigated in the type strains of Azospirillum lipoferum and Azospirillum brasilense grown aerobically with (NH4)2SO4 as the nitrogen source. When grown on fructose, the former species possessed a complete Entner-Doudoroff pathway, whereas the latter species lacked activity for glucose-6-phosphate dehydrogenase. Both species possessed a complete catabolic Embden-Meyerhof-Parnas pathway. Neither species possessed the key enzyme of the hexose monophosphate pathway, 6-phosphogluconate dehydrogenase. Both species could phosphorylate fructose to fructose-1-phosphate by means of a phosphoenolpyruvate-phosphotransferase system, and high activities of 1-phosphofructokinase occurred. Both species possessed glucokinase activity, but only A. lipoferum had hexokinase activity; moreover, the cells of A. brasilense were nearly impermeable to glucose, accounting for the inability of this species to grow on glucose. Both species possessed pyruvate dehydrogenase, a complete tricarboxylic acid cycle, a glyoxylate shunt, and malic enzyme. Analysis of the acidic end products for both species indicated the formation of only small amounts of various organic acids, and most of the titratable acidity was due to utilization of the ammonium ions of the medium. Gluconic acid was not formed during growth of either species on fructose but was detected during growth of A. lipoferum on glucose; this species also possessed an NADP-linked glucose dehydrogenase and gluconokinase.
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PMID:Fructose catabolism in Azospirillum brasilense and Azospirillum lipoferum. 673 86

The effect of dissolved oxygen concentration on the metabolism of glucose in Pseudomonas aeruginosa was studied with chemostat cultures using both single-step and gradual transitions from either ammonium or glucose limitation to oxygen limitation and studying transient and steady states. The pathway of glucose metabolism was regulated by the availability of oxygen. The organism responded to oxygen limitation by adjusting its metabolism of glucose from the extracellular direct oxidative pathway, which produces gluconate and 2-oxogluconate, to the intracellular phosphorylative route. This change was a consequence of decreased activities of glucose dehydrogenase and gluconate dehydrogenase and of the transport systems for gluconate and 2-oxogluconate, and an increased activity of glucose transport, while relatively high activities of hexokinase and glucose-6-phosphate dehydrogenase were maintained. Citrate synthase, isocitrate dehydrogenase and malate dehydrogenase activities responded to changes in dissolved oxygen concentration rather than to changes in the glucose or ammonium concentrations. The effect of oxygen limitation on the oxo-acid dehydrogenases and aconitase was probably due, wholly or in part, to repression by glucose consequent upon the increase in residual glucose concentration. Succinate dehydrogenase was repressed by an increase in ammonium concentration under an oxygen limitation.
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PMID:The role of oxygen in the regulation of glucose metabolism, transport and the tricarboxylic acid cycle in Pseudomonas aeruginosa. 708 92

A method for the manual determination of glucose in hemolysate is described. Both hexokinase/G6P-DH (e.g. Glucoquant) and glucose dehydrogenase can be used as reagents. The two methods correlate satisfactorily with an approved method. Correlation with an automated method: Gluc-DH: r = 0,98323; hexokinase/G6P-DH: r = 0,94172.
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PMID:[Glucose determination in the hemolysate, manual analysis]. 737

Two hexokinases were characterized in Schizosaccharomyces pombe: hexokinase 1, with a low phosphorylation coefficient on glucose (Km 8.5 mM) and hexokinase 2, a kinetically conventional hexokinase. Genes hxk1+ and hxk2+ encoding these enzymes were cloned and sequenced. Disruption of hxk1+ had no effect on growth but disruption of hxk2+ doubled the generation time in glucose. Spores carrying the double disruption hxk1+ hxk2+ did not grow on glucose or fructose after one week. Expression of hxk1+ increased strongly during growth in fructose or glycerol. Expression of hxk2+ was highest during growth in glycerol. A NADP-dependent glucose dehydrogenase was detected, but not a glucokinase.
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PMID:Schizosaccharomyces pombe possesses an unusual and a conventional hexokinase: biochemical and molecular characterization of both hexokinases. 854 30

The aim of the study was to evaluate a portable photometer, HemoCue Blood Glucose Analyzer, in the instant diagnosis of hypoglycaemia in newborns. The HemoCue is a simple, easy-to-handle photometer; with an analysis time of less than 240 s, it utilizes a modified glucose dehydrogenase method in 5 microliters whole blood. The HemoCue method was compared to a hexokinase method for deproteinized whole blood in a total of 118 samples from 58 newborns. The linear regression for these samples was Y = 1.19 x -1.02 (range 0.7-7.2 mmol/L), r = 0.90. Ten samples were < or = 2.0 mmol/L with both methods and 37 samples were < or = 2.0 mmol/L with the HemoCue method. The average difference (D) for each sample (n = 118) and the standard deviation (SD) for the difference were 0.45 +/- 0.46 mmol/L. Blood samples with a mean value with both methods < or = 2.0 mmol/L (n = 20) had a D and SD of 0.71 +/- 0.29 mmol/L. When testing for linearity at low glucose concentrations, the HemoCue method gave significantly lower values compared to an ideal line. The HemoCue method has several advantages in the analysis of glucose in newborns: short analysis time, small sample size, and no influence from glycolysis. However, in our investigation, falsely low values occurred, especially in the low measuring range, so the HemoCue method is not suitable in the diagnosis of hypoglycaemia in newborns.
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PMID:Evaluation of HemoCue Blood Glucose Analyzer for the instant diagnosis of hypoglycaemia in newborns. 945 95

An improved method has been developed for the assay of hexokinase (EC 2.7.1.1) levels in human tissue homogenates. The enzyme is quantitated by the spectrophotometric measurement, at 340 nm, of NADPH formed according to the reaction scheme: [formula: see text] In tissue homogenates a number of enzymes are present which can interfere with the assay by reacting with substrates or products of the assay reactions. In the described procedure hexokinase is assayed directly in homogenates under conditions in which the effect of possible contaminating enzymes (glucose dehydrogenase, EC 1.1.1.47; glucose 6-phosphatase, EC 3.1.3.9; glucose phosphate isomerase, EC 5.3.1.9; 6-phosphogluconate dehydrogenase EC 1.1.1.44; and NADP-reducing enzymes) are eliminated. Precision studies on the assay gave within-day reproducibility of 4.3% (CV) on a tissue having a mean activity of 1.68 U/g of tissue, and day-to-day variability of 15% (CV) for a tissue averaging 1.83 U/g of tissue.
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PMID:An improved assay for hexokinase activity in human tissue homogenates. 976 31

There is an urgent need to develop technology for continuous in vivo glucose monitoring in subjects with diabetes mellitus. Problems with existing devices based on electrochemistry have encouraged alternative approaches to glucose sensing in recent years, and those based on fluorescence intensity and lifetime have special advantages, including sensitivity and the potential for non-invasive measurement when near-infrared light is used. Several receptors have been employed to detect glucose in fluorescence sensors, and these include the lectin concanavalin A (Con A), enzymes such as glucose oxidase, glucose dehydrogenase and hexokinase/glucokinase, bacterial glucose-binding protein, and boronic acid derivatives (which bind the diols of sugars). Techniques include measuring changes in fluorescence resonance energy transfer (FRET) between a fluorescent donor and an acceptor either within a protein which undergoes glucose-induced changes in conformation or because of competitive displacement; measurement of glucose-induced changes in intrinsic fluorescence of enzymes (e.g. due to tryptophan residues in hexokinase) or extrinsic fluorophores (e.g. using environmentally sensitive fluorophores to signal protein conformation). Non-invasive glucose monitoring can be accomplished by measurement of cell autofluorescence due to NAD(P)H, and fluorescent markers of mitochondrial metabolism can signal changes in extracellular glucose concentration. Here we review the principles of operation, context and current status of the various approaches to fluorescence-based glucose sensing.
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PMID:Fluorescence-based glucose sensors. 1585 25

A high-performance monitoring system for human blood glucose levels was developed using microchip electrophoresis with a plastic chip. The combination of reductive amination as glucose labeling with fluorescent 2-aminoacridone (AMAC) and glucose-borate complex formation realized the highly selective detection of glucose even in a complex matrix such as a blood sample. The migration time of a single peak, observed on an electropherogram of AMAC-labeled plasma, closely resembled that of glucose standard solution. The treatment of plasma with hexokinase or glucokinase for glucose phosphorylation resulted in a peak shift from approximately 145 to 70 s, corresponding to glucose and glucose-6-phosphate, respectively. A double-logarithm plot revealed a linear relationship between glucose concentration and fluorescence intensity in the range of 1-300 microM of glucose (r(2) = 0.9963; p <0.01), and the detection limit was 0.92 microM. Furthermore, blood glucose concentrations estimated from the standard curves of three subjects were compared with results obtained by conventional colorimetric analysis using glucose dehydrogenase. Good correlation was observed between methods according to simple linear regression analysis (p <0.05). The reproducibility of the assay was about 6.3-9.1% (RSD) and the within-days and between-days reproducibility were 1.6-8.4 and 5.2-7.2%, respectively. This system enables us to determine blood glucose with high sensitivity and accuracy, and will be applicable to clinical diagnosis.
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PMID:Determination of human blood glucose levels using microchip electrophoresis. 1764 93

A novel concept for a dual-enzyme-based microbiosensor for the detection of adenosine-5'-triphosphate (ATP) was developed. The employed enzymes pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH) and hexokinase were entrapped, using pH-shift-induced precipitation of electrodeposition paint (EDP) at platinum microelectrodes (diameter of 25 microm). PQQ-GDH is known showing a superior activity for glucose conversion at the relevant conditions (low oxygen concentration) for ATP detection in targeted biomedical studies. For immobilizing the two enzymes PQQ-GDH and hexokinase, the deposition conditions of EDP Resydrol AY498w/35WA were adapted to ensure high immobilization rates. Prior to ATP sensing, the conversion of glucose, which is the co-substrate for both enzymatic reactions, was optimized. Optimization was targeted towards ATP measurements in biomedical environments by optimizing the PQQ-GDH sensor for glucose. Therefore, different mediators were tested regarding their electron transfer rate and their compatibility with the enzyme: free-diffusing N-methylphenazonium methyl sulfate (PMS) and ferrocenemethanol, and an immobilized chromium hexacyanoferrate layer at platinum electrode. Free-diffusing ferrocenemethanol reveals high sensitivity towards glucose of 1.5 +/- 0.4 nA/mM. In a next step, hexokinase was co-entrapped in the polymer film resulting in a sensitivity of up to 290 pA/microM.
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PMID:Developmental aspects of amperometric ATP biosensors based on entrapped enzymes. 1977 27

Study refers comparison of three methods for glucose determination - precision (repeatability, reproducibility), traceability to SRM 965a NIST, comparability in blood-pools and in patients' samples: Electrochemical determination on Super GL (DiaSys, Germany) in hemolyzate - GL method, spectrophotometric determination using hexokinase (Glucose System Reagent 800, Olympus) - HKL method - and using glucose dehydrogenase (Glucose Gluc-DH, EcolineS+, DiaSys, Germany) - GDL method - in hemolyzate. For showing differences between the concentration of glucose in hemolyzed blood and corresponding plasma, spectrophotometric determination using hexokinase in plasma was used (Glucose System Reagent 800, Olympus) - HKP method. Coefficients of variation characterizing precision under repeatability and reproducibility conditions are not higher than 3.0% for the GL method, 6.3% for the GDL method and 15.8% for the HKL method with low sensitivity. For glucose concentration less than 8 mmol/l, HKL tends to give lower results than GDL, and GL tends to give higher results than GDL. For glucose concentration about 2 mmol/l, the results of glucose in plasma - HKP method - tend to be significantly lower (by more than ten percent) than in corresponding total (hemolyzed) blood. HKL method can be reasonably used in a high number of parallel determinations. For glucose 8 mmol/l and lower, comparability of results given by HKL, GDL and GL methods gradually worsens, while for glucose between 8 and 34 mmol/l results of the three mentioned methods are well comparable.
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PMID:Comparison of three methods for determination of glucose. 2035 37


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