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)

An automated method is described for the enzymatic determination of adenosine-5'-triphosphate (ATP) in meat using hexokinase (EC 2.7.1.1) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49) in the range of 0-115 micrograms/ml. THe NADPH formed is measured spectrophotometrically at 340 nm. ATP can be analysed at a rate of forty samples per hour.
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PMID:Automated enzymatic determination of ATP in bovine muscle tissue. 731 21

Resealed red cell ghosts were prepared at a final dilution of 1:325 from normal and G6PD-deficient cells. The activity of the HMS and concentrations of G6P, ATP, and total and reduced nictinamide adenine dinucleotide phosphate were determined after incubation in the presence of 0 and 100 micrometer methylene blue. The results indicate that the HMS is still under ununexplained restraint in the resealed cells but that the restraint has been reduced between twofold and fourfold from that observed in the intact normal red cells. The addition of various combinations of ATP, hexokinase, and methylene blue led to the demonstration that the unexplained restraint is not significantly correlated with levels of ATP or G6P. As with intact red cells, however, the explained restraint is greatest under conditions that cause the level of NADP+ to be low and that of NADPH to be high.
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PMID:Regulation of glucose-6-phosphate dehydrogenase. II. Resealed red cell ghosts. 738 Dec 97

beta-Fructofuranosidase, alpha-glucosidase, beta-glucosidase, alpha-mannosidase, beta-mannosidase, sucrose phosphorylase, glucosyltransferase and fructosyltransferase were separated by isoelectric focusing and sensitively detected to be slightly diffuse and insoluble spots in thin-layer gels, supported by a glass plate, by release of monosugars or a sugar phosphate, followed by conversion to glucose-6-phosphate (G6P) and then by reduction of NADP+ to NADPH, terminated by the formation of reduced Nitroblue Tetrazolium (NBT). Approximately 1-10 mU of enzyme was focused and the gel, after washing with a buffer, was partially dried and directly stained by uniformly spreading on the gel surface a staining medium containing sucrose or nitrophenyl glycosides as substrates, intermediary enzymes such as hexokinase, mutase and/or isomerase, NADP+, ATP, Mg+, phenazine methosulfate (PMS) and NBT. Specific staining procedures for each of these activities, on sucrose or on the glycosides as substrates, and staining procedures for multiple activities are described, with the conditions necessary for optimal development.
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PMID:Glucose, fructose, mannose and/or glucose-1-phosphate-releasing activity stains for glycosidases and glycosyltransferases in gels after isoelectric focusing. 751 61

The structure of the isocitrate dehydrogenase (IDH) complex with bound alpha-ketoglutarate, Ca2+, and NADPH was solved at 2.7-A resolution. The alpha-ketoglutarate binds in the active site at the same position and orientation as isocitrate, with a difference between the two bound molecules of about 0.8 A. The Ca2+ metal is coordinated by alpha-ketoglutarate, three conserved aspartate residues, and a pair of water molecules. The largest motion in the active site relative to the isocitrate enzyme complex is observed for tyrosine 160, which originally forms a hydrogen bond to the labile carboxyl group of isocitrate and moves to form a new hydrogen bond to Asp 307 in the complex with alpha-ketoglutarate. This triggers a number of significant movements among several short loops and adjoining secondary structural elements in the enzyme, most of which participate in dimer stabilization and formation of the active-site cleft. These rearrangements are similar to the ligand-binding-induced movements observed in globins and insulin and serve as a model for an enzymatic mechanism which involves local shifts of secondary structural elements during turnover, rather than large-scale domain closures or loop transitions induced by substrate binding such as those observed in hexokinase or triosephosphate isomerase.
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PMID:Structure of isocitrate dehydrogenase with alpha-ketoglutarate at 2.7-A resolution: conformational changes induced by decarboxylation of isocitrate. 836 1

In this study changes in alternative pathways of glucose metabolism are examined in the rat lens using radiolabelled glucose in a 1 hr in vitro incubation of 50 mM or 10 mM glucose with or without 0.1 mM phenazine methosulphate (PMS). PMS which reoxidizes NADPH ensures that the pentose phosphate pathway (PPP) is not limited by the supply of NADP+. The data shows that maximal activation of the PPP (with PMS) is 40% greater at high glucose concentrations than normal glucose. This difference in maximal stimulation may be explained by the increase glucose uptake in the hyperglycaemic incubation. In the high-glucose incubation with PMS, hexokinase activity and the glucose 6-phosphate pool is not limiting for the PPP. Under these conditions, PMS alter the NAD+/NADH and NADP+/NADPH ratio. The change in the redox state alters the flux through the polyol pathway, the glycerol 3-phosphate shuttle and the glycolytic control sites, glyceraldehyde 3-phosphate, pyruvate and lactate dehydrogenases. These results are discussed in relation to hyperglycaemia-induced oxidative stress.
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PMID:The effect of phenazine methosulphate on intermediary pathways of glucose metabolism in the lens at different glycaemic levels. 865 4

The uptake and release properties of Ca2+ by several subcellular fractions of the bovine adrenal medulla were investigated. Investigation by the 45Ca2+ tracer method showed that permeabilized cells and the fractions of mitochondria (MT) and microsomes (MC) caused ATP-dependent Ca2+ uptake in a Ca2+ concentration-dependent manner (pCa 8-4), whereas permeabilized cells and the fractions of secretory granules (SG) were able to accumulate a significant amount of Ca2+ even in the absence of ATP, which was completed by the addition of hexokinase and glucose. In these organelle fractions, Ca2+ uptake in the presence of ATP at pCa 7 and pCa 5.8 was well-correlated with the activity of the NADPH cytochrome c reductase (marker enzyme for the endoplasmic reticulum) and cytochrome c oxidase (marker enzyme for mitochondria), respectively. As detected by Fura-2 ratiometry, both inositol 1,4,5-trisphosphate (IP3) and caffeine caused concentration-dependent Ca2+ releases from permeabilized cells and MC, but not from MT and SG. In an ATP-depleted condition, homogenates still took up a significant amount of Ca2+ but was not able to respond to IP3 and caffeine. These results suggest that the endoplasmic reticulum is a major Ca(2+)-storing organelle, which releases Ca2+ in response to IP3 and caffeine in bovine adrenal chromaffin cells.
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PMID:Inositol 1,4,5-trisphosphate- and caffeine-sensitive Ca(2+)-storing organelle in bovine adrenal chromaffin cells. 901 39

In order to reveal sequel of events responsible for increase in red cell cytosolic glucose-6 phosphate (G-6P) content of diabetic patients the enzyme producing and transforming G-6P were assayed. Increase in the activity of hexokinase and decrease in phosphoglucoisomerase activity was observed in mild insulin dependent diabetes mellitus (mIDDM) rat erythrocytes. Increase and decrease in activity of hexokinase and phosphoglucoisomerase respectively will increase the cytosolic glucose-6 phosphate content. Thus any substance which autoregulate the activity of hexokinase and maintains critical level of G-6P necessary for generation of ATP and coenzymes (NADPH & NAD+) in the prevailing hyperglycemic state can be a potential therapeutic agent for diabetic patients.
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PMID:Activation of hexokinase by mild insulin dependent diabetes mellitus in rat erythrocytes. 937 21

A common characteristic of tumor cells is the constant overexpression of glycolytic and glutaminolytic enzymes. In tumor cells the hyperactive hexokinase and the partly inactive pyruvate kinase lead to an expansion of all phosphometabolites from glucose 6-phosphate to phosphoenolpyruvate. In addition to the glycolytic phosphometabolites, synthesis of their metabolic derivatives such as P-ribose-PP, NADH, NADPH, UTP, CTP, and UDP-N-acetyl glucosamine is also enhanced during cell proliferation. Another phosphometabolite derived from P-ribose-PP, AMP, inhibits cell proliferation. The accumulation of AMP inhibits both P-ribose-PP-synthetase and the increase in concentration of phosphometabolites derived from P-ribose-PP. In cells with low glycerol 3-phosphate and malate-aspartate shuttle capacities the inhibition of the lactate dehydrogenase by low NADH levels leads to an inhibition of glycolytic ATP production. Several tumor-therapeutic drugs reduce NAD and NADH levels, thereby inhibiting glycolytic energy production. The role of AMP, NADH, and NADPH levels in the success of chemotherapeutic treatment is discussed.
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PMID:The role of phosphometabolites in cell proliferation, energy metabolism, and tumor therapy. 938 92

As part of the development of structured models for the metabolism of myeloma cells in suspension culture, a study was made of the subcellular localization of key enzymes of glucose and glutamine metabolism. Steady state chemostat cultures of the mouse myeloma SP2/0-Ag14 were used as a reproducible source of biomass. Homogenates of the cells, obtained via mechanical disruption, were separated into a mitochondrial and a cytosolic fraction via differential centrifugation. The following conclusions are drawn: (1) approximately one fifth of the hexokinase activity of cell-free homogenates is associated with the mitochondria; (2) a malate-aspartate shuttle may operate for oxidation of cytosolic NADH, as indicated by high levels of malate dehydrogenase and aspartate aminotransferase in both particulate and soluble fractions; (3) the pentose phosphate pathway and isocitrate dehydrogenase may contribute to the provision of cytosolic NADPH; (4) phosphoenolpyruvate carboxykinase and pyruvate kinase, which are present in high activities, are exclusively cytosolic and probably play a key role in glutamine metabolism; (5) oxidation of glutamine via these enzymes leads to the formation of pyruvate that enters the same pool as pyruvate generated by glycolysis. As a result, lactate and alanine formation can occur from both glucose and glutamine.
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PMID:Subcellular localization of enzyme activities in chemostat-grown murine myeloma cells. 965 Feb 85

Hexokinase and D-glucose-6-phosphate dehydrogenase (G6PDH) from Schizosaccharomyces pmbe have been purified 250-fold by an identical three-step. Both enzymes are dimeric with a molecular mass of 88 kDa for the kinase and 112 kDa for the dehydrogenase. Steady-state kinetic studies were performed on hexokinase and G6PDH, which form the glucose phosphate branch of the oxidative pentose phosphate pathway of S. pombe (fission yeast). Hexokinase promotes Mg(2+)-activated phosphorylation of D-glucose by the equilibrium random Bi Bi mechanism with formation of the abortive enzyme-ADP-glucose complex. ADP inhibits the kinase competitively versus ATP and noncompetitively versus D-glucose. The Mg2+ activation of hexokinase is associated with an increase in the maximal velocity by its interaction with the ternary complex to facilitate the transfer of the phosphoryl group. G6PDH catalyzes NADP(+)-linked oxidation of D-glucose-6-phosphate by the ordered Bi Bi mechanism with NADP+ as the leading reactant. High NADP+ concentration inhibits the dehydrogenase by forming the dead-end ternary complex. In addition, G6PDH is also subjected to product inhibition by NADPH and noncompetitive inhibition by A(G)TP. Thus, the oxidative pentose phosphate pathway in S. pombe may be regulated via inhibition of hexokinase by ADP in conjunction with inhibition of G6PDH by NADPH and ATP.
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PMID:Purification and kinetic characterization of hexokinase and glucose-6-phosphate dehydrogenase from Schizosaccharomyces pombe. 966 12


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