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

Recent studies indicate a key role of aquaporin (AQP) 4 in astrocyte swelling and brain edema and suggest that AQP4 inhibition may be a new therapeutic way for reducing cerebral water accumulation. To understand the physiological role of AQP4-mediated astroglial swelling, we used 21-nucleotide small interfering RNA duplexes (siRNA) to specifically suppress AQP4 expression in astrocyte primary cultures. Semiquantitative RT-PCR experiments and Western blot analysis showed that AQP4 silencing determined a progressive and parallel reduction in AQP4 mRNA and protein. AQP4 gene suppression determined the appearance of a new morphological cell phenotype associated with a strong reduction in cell growth. Water transport measurements showed that the rate of shrinkage of AQP4 knockdown astrocytes was one-half of that of controls. Finally, cDNA microarray analysis revealed that the gene expression pattern perturbed by AQP4 gene silencing concerned ischemia-related genes, such as GLUT1 and hexokinase. Taken together, these results indicate that 1) AQP4 seems to be the major factor responsible for the fast water transport of cultured astrocytes; 2) as in skeletal muscle, AQP4 is a protein involved in cell plasticity; 3) AQP4 alteration may be a primary factor in ischemia-induced cerebral edema; and 4) RNA interference could be a new potent tool for studying AQP pathophysiology in those organs and tissues where they are expressed.
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PMID:Inhibition of aquaporin-4 expression in astrocytes by RNAi determines alteration in cell morphology, growth, and water transport and induces changes in ischemia-related genes. 1282 87

Sugars like glucose and fructose induce death of yeast cells within a few hours, in the absence of additional nutrients to support growth, while cells incubated in water remain viable for weeks. This sugar-induced cell death (SICD) by glucose and fructose required glucose or fructose phosphorylation since yeast cells deficient in hexose phosphorylation did not die. However, when hexose phosphorylation is restored by complementation with Arabidopsis thaliana hexokinase, the cells died. The affinity of A. thaliana hexokinase is about 400 times higher for glucose than for fructose, therefore, A. thaliana hexokinase was further utilized to study the role of hexose phosphorylation in SICD. The rate of SICD of hexokinase-deficient yeast cells expressing A. thaliana hexokinase was significantly slower in fructose than in glucose, indicating that SICD is determined by the rate of hexose phosphorylation. The significance of hexose phosphorylation and its role in SICD is discussed.
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PMID:Sugar induced cell death in yeast is dependent on the rate of sugar phosphorylation as determined by Arabidopsis thaliana hexokinase. 1455 68

The binding of D-glucose to hexokinase PII at 25 degrees C and pH 8.7 has been investigated by a combination of ultrasonic velocimetry, high precision densimetry, and fluorescence spectroscopy. The binding of glucose to the enzyme results in significant dehydration of the two interacting molecules, while the intrinsic coefficient of adiabatic compressibility of hexokinase slightly decreases. Glucose-hexokinase association is an entropy-driven process. The favorable change in entropy results from compensation between two large contributions. The binding-induced increase in hydrational entropy slightly prevails over the decrease in the configurational entropy of the enzyme. Taken together, our results emphasize the crucial role of water in modulating the energetics of protein recognition.
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PMID:Volumetric and spectroscopic characterizations of glucose-hexokinase association. 1462 93

Life began in a bath of water and has never escaped it. Cellular function has forced the evolution of many mechanisms ensuring that cellular water concentration has never changed significantly. To free oneself of any conceptual distinction among all small molecules, solutes and solvents, means that experiments to probe water's specific role in molecular function can be designed like any classical chemical reaction. Such an 'osmotic stress' strategy will be described in general and for an enzyme, hexokinase. Water behaves like a reactant that competes with glucose in binding to hexokinase, and modulates its conformational change and activity. This 'osmotic stress' strategy, now applied to many very different systems, shows that water plays a significant role, energetically, in most macromolecular reactions. It can be required to fill obligatory space, it dominates nearest non-specific interactions between large surfaces, it can be a reactant modulating conformational change; all this in addition to its more commonly perceived static role as an integral part of stereospecific intramolecular structure.
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PMID:Probing the role of water in protein conformation and function. 1530 82

A fast, simple, and accurate method, using only standard laboratory equipment, was developed for the quantification of glucose, fructose, sucrose, and inulin/oligofructose in different food matrixes. Samples were extracted using boiling water and hydrolyzed with sucrase and fructanase. Sugars were determined in the initial extract and in both hydrolysates using an enzymatic, spectrophotometric kit for glucose and fructose determination with hexokinase, glucose-6-phosphate dehydrogenase, and phosphoglucose isomerase. Calculations of sucrose and inulin/oligofructose were based only on fructose measurement. Glucose results of the hydrolysates were not used for inulin/oligofructose calculations because of possible interference. Released glucose by the hydrolysis of maltose or by possible partial hydrolysis of other compounds like maltodextrines, starch, lactose, or maltitol could interfere in the measurement of the sucrase and the fructanase hydrolysates. To validate the method, a wide range of different food matrixes and different amounts of inulin/oligofructose (1-54%) were analyzed. Mean recovery +/- relative standard deviation (RSD) for inulin or oligofructose was 96.0 +/- 5.3%. The RSDr for inulin/oligofructose measured on 35 food samples, analyzed in duplicate, was 5.9%. Accuracy and precision of the method were less for samples with large concentrations of sucrose, maltose, maltodextrines, or starch (ratio to inulin/oligofructose >4 to 1). Precision and accuracy were comparable with those of the ion exchange chromatographic method AOAC 997.08 and the enzymatic, spectrophotometric method AOAC 999.03. In contrast to 999.03, this method allows the accurate quantification of both GFn and Fn forms.
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PMID:Enzymatic, spectrophotometric determination of glucose, fructose, sucrose, and inulin/oligofructose in foods. 1549 79

A series of nine organometallic technetium-99m and rhenium complexes of glucose are presented and characterized in vitro regarding their potential as surrogates of [18F]-2-fluoro-desoxy glucose ([18F]-FDG). The glucose derivatives are functionalized at positions C-1, C-2, C-3, and C-6. Different spacer lengths and chelating systems have been introduced at these sites. For the (radio)labeling, the organometallic precursors [99mTc(H2O)3(CO)3]+ and [ReBr3(CO)3](2-) respectively have been used. The resulting complexes have been characterized chemically and radiochemically. The formation of uniform products has been observed on the macroscopic (Re) and no-carrier-added level (99mTc). The Tc-99m complexes revealed good inertness against ligand exchange (Cys and His) and excellent stability in physiological buffered saline as well as in human plasma over a period of 24 h at 37 degrees C. The rhenium complexes have been tested for competitive inhibition of the (yeast) hexokinase. Only for C-2 derivatized glucose complexes with extended spacer functionalities Ki values in the millimolar and sub-millimolar range have been observed. In silico molecular docking experiments supported these experimental findings. However, the competitive inhibitors are not recognized as a pseudosubstrate of hexokinase. The cellular uptake of all 99mTc-complexes into HT-29 colon carcinoma cells via Glut1 was generally low and unspecific independent of the position at the hexose ring, the chelating systems, or the overall charge of the corresponding metal complexes. The current results seem to preclude the use of these compounds as [18F]-FDG surrogates primarily due to the low cellular uptake via Glut1.
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PMID:Synthesis and in vitro characterization of organometallic rhenium and technetium glucose complexes against Glut 1 and hexokinase. 1565 81

A new enzymatic method for glucose determination is described. It allows measurement of glucose concentration as low as 10 M. Such sensitivity makes this method particularly appropriate for estimation of glucose in natural-water bodies, generally without prior concentration or extraction. The method is based on the reaction between glucose and adenosine 5'-triphosphate, catalyzed by hexokinase to form glucose-6-phosphate. The amount of adenosine 5'-triphosphate consumed in this reaction, which is directly proportional to the amount of glucose present in the sample, is measured by the luciferin-luciferase assay. The optimal conditions for glucose determination by this method have been defined as follows: 20 min of incubation at 30 degrees C, magnesium concentration of 10 M, and pH in the range of 7.5 to 10.5. The specificity of the assay to different carbohydrates has also been studied. Recovery of known amounts of glucose added to Lake Kinneret water was in the range of 80 to 114%. Application of this method is demonstrated in eight monthly profiles of the glucose content in Lake Kinneret.
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PMID:Sensitive enzymatic assay for glucose determination in natural waters. 1634 45

The present study was conducted to evaluate the adverse effects of chlorpyrifos on the key enzymes of carbohydrate metabolism in liver, and also to assess the role of zinc under these toxic conditions. Male Sprague-Dawley (SD) rats received either oral chlorpyrifos treatment (13.5 mg/kg body weight in corn oil) every alternate day, zinc alone (227 mg/l in drinking water), or combined chlorpyrifos and zinc treatments for a total duration of 8 weeks. The effects of different treatment regimens were studied on various enzymes of carbohydrate metabolism in the rat livers, which included hexokinase, glucose-6-phosphatase, fructose-1,6-diphosphatase, glycogen phosphorylase, succinate dehydrogenase (SDH), lactate dehydrogenase (LDH) and the levels of glycogen. In vitro uptake of (14)C-D-glucose was also assessed in liver slices after similar treatments. Chlorpyrifos intoxication resulted in a significant increase in the activities of glucose-6-phosphatase and glycogen phosphorylase, whereas, it caused a significant inhibition in the levels of hexokinase, SDH, LDH and glycogen content. However, zinc treatment to chlorpyrifos-intoxicated animals was able to normalize the activities of most of these enzymes to either close to, or within normal limits. Chlorpyrifos intoxication demonstrated significantly inhibited (14)C-D-glucose uptake in liver slices, which again was reversed to normal limits following simultaneous zinc treatment. Levels of metallothionein were also found to be depressed in chlorpyrifos-treated animals, but tended to increase significantly on co-administration of zinc to chlorpyrifos-treated group. Hence, the present study clearly suggests that zinc plays an important role in regulating the hepatic activities of the enzymes involved in carbohydrate metabolism under conditions of chlorpyrifos toxicity.
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PMID:Chlorpyrifos-induced alterations in the activities of carbohydrate metabolizing enzymes in rat liver: the role of zinc. 1637 99

Osmolytes of the polyol series are known to accumulate in biological systems under stress and stabilize the structures of a wide variety of proteins. While increased surface tension of aqueous solutions has been considered an important factor in protein stabilization effect, glycerol is an exception, lowering the surface tension of water. To clarify this anomalous effect, the effect of a series of polyols on the thermal stability of a highly thermolabile two domain protein yeast hexokinase A has been investigated by differential scanning calorimetry and by monitoring loss in the biological activity of the enzyme as a function of time. A larger increase in the T(m) of domain 1 compared with that of domain 2, varying linearly with the number of hydroxyl groups in polyols, has been observed, sorbitol being the best stabilizer against both thermal as well as urea denaturation. Polyols help retain the activity of the enzyme considerably and a good correlation of the increase in T(m) (DeltaT(m)) and the retention of activity with the increase in the surface tension of polyol solutions, except glycerol, which breaks this trend, has been observed. However, the DeltaT(m) values show a linear correlation with apparent molal heat capacity and volume of aqueous polyol solutions including glycerol. These results suggest that while bulk solution properties contribute significantly to protein stabilization, interfacial properties are not always a good indicator of the stabilizing effect. A subtle balance of various weak binding and exclusion effects of the osmolytes mediated by water further regulates the stabilizing effect. Understanding these aspects is critical in the rational design of stable protein formulations.
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PMID:Stabilization of yeast hexokinase A by polyol osmolytes: correlation with the physicochemical properties of aqueous solutions. 1682 62

This work describes the use of 3-hydroxy-4-pyridinone ligands for binding the [M(CO)(3)](+) core (M = Re, Tc) in the context of preparing novel Tc(I) and Re(I) glucose conjugates. Five pyridinone ligands bearing pendent carbohydrate moieties, HL(1-5), were coordinated to the [M(CO)(3)](+) core on the macroscopic scale (M = Re) and on the tracer scale (M = (99m)Tc, (186)Re). On the macroscopic scale the complexes, ReL(1-5)(CO)(3)(H(2)O), were thoroughly characterized by mass spectrometry, IR spectroscopy, UV-visible spectroscopy, elemental analysis, and 1D/2D NMR spectroscopy. Characterization confirmed the bidentate coordination of the pyridinone and the pendent nature of the carbohydrate and suggests the presence of a water molecule in the sixth coordination site. In preliminary biological evaluation, both the ligands and complexes were assessed as potential substrates or inhibitors of hexokinase, but showed no activity. Labeling via the [(99m)Tc(CO)(3)(H(2)O)(3)](+) precursor gave the tracer species (99m)TcL(1-5)(CO)(3)(H(2)O) in high radiochemical yields. Similar high radiochemical yields when labeling with (186)Re were facilitated by in situ preparation of the [(186)Re(CO)(3)(H(2)O)(3)](+) species in the presence of HL(1-5) to give (186)ReL(1-5)(CO)(3)(H(2)O). Stability challenges, incubating (99m)TcL(1-5)(CO)(3)(H(2)O) in the presence of excess cysteine and histidine, confirmed complex stability up to 24 h.
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PMID:Carbohydrate-appended 3-hydroxy-4-pyridinone complexes of the [M(CO)3]+ core (M = Re, 99mTc, 186Re). 1698 43


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