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)

A simple device capable of measuring almost any reactant in an enzyme-catalyzed reaction is created when an enzyme is immobilized onto one thermal sensor of a differential thermometer. Experiments are described in which two thermistors, one bare and one coated with immobilized enzyme, are immersed in a well-stirred solution. The response of this device to increases in glucose-ATP concentration was observed using hexokinase (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1), and to increases in glucose concentration using glucose oxidase (beta-D-glucose:oxygen 1-oxidoreductase, EC 1.1.3.4). A simple model is presented whose predictions are in reasonable agreement with the experimental results.
Biochim Biophys Acta 1976 Dec 08
PMID:Experiments and calculations concerning a thermal enzyme probe. 100 14

Human erythrocyte hexokinase (EC 2.7.1.1) is inhibited competitively with respect to Mg-ATP2- by uncomplexed Mg2+ (Ki = 16--18 mM) and ATP4- (Ki = 1.6 mM). No real activation by low concentrations of Mg2+ could be detected and no allosteric behaviour was observed under the conditions tested. The temperature dependence of the enzyme was studied in relationship to the presence of Mg2+ or ATP4-. At equal concentrations of Mg2+ and ATP4- a break in the Arrhenius plot was observed at 27.5 degrees C, the higher temperature form of the enzyme having the lower activation energy. This break point in the Arrhenius plot was shifted to 36 degrees C in the presence of 5 mM Mg2+. A straight-line relationship was observed in the presence of 2.5 mM ATP4-. The Km for Mg-ATP2- showed a linear increase at temperatures over about 36 degrees C independent of the presence of Mg2+ or ATP4-. The nature of these phenomena is discussed.
Biochim Biophys Acta 1976 Dec 08
PMID:Kinetics of human erythrocyte hexokinase. Influence of temperature, ATP4- and magnesium ions. 100 15

Enzyme abnormalities are frequently found in the red cells of patients with various acquired blood disorders. In leukaemias, preleukaemic states and bone marrow insufficiencies with or without sideroblastosis, changes in enzyme activity are usually characterized by the coexistence of deficiency of some enzymes and an increased activity of others. The most frequently decreased activities are those of pyruvate kinase, phosphofructokinase,2,3-diphosphoglycerate mutase and adenylate kinase; the most frequently increased activities are those of hexokinase, aldolase, enolase, 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenase. In primary myelofibrosis and in polycythaemia rubra vera, enzyme deficiencies are infrequent and differ from those observed in leukaemias and related disorders. Phosphohexose isomerase and phosphoglucomutase deficiencies seem relatively specific for polycythaemia rubra vera. Explanations for the acquired enzymopathies are still at the stage of hypothesis. The theory of multiple genetic damage may explain some findings but has not yet been proved right. The possibility of post-translational molecular modification is suggested as a working hypothesis.
Br J Haematol 1975 Dec
PMID:Acquired erythroenzymopathies in blood disorders: study of 200 cases. 107 44

A continuous flow method is described for the determination of glucose in haemolysates and other materials with hexokinase/glucose-6-phosphate dehydrogenase as reagents. It is a micro-method (20 microliter) which can be used with the 2. generation auto-analyzer. The new method was compared with a hexokinase manual method.
Z Klin Chem Klin Biochem 1975 Dec
PMID:[A micromethod for the determination of glucose in 20 microliter samples with the autoanalyzer (author's transl)]. 120 82

A previous method for red cell fractionation by density gradient centrifugation, using a swing-out rotor, has been scaled up to deal with larger volumes of red cells. This method, involving the use of a zonal rotor, is described and has been applied to the study of the decay of hexokinase in the red cells of normal individuals. Hexokinase activity was seen to fall very rapidly in the young cells followed by a much more gradual decline in older cells. It is estimated that the mature red cell probably contains no more than 2-3% of the hexokinase activity originally present in the reticulocyte. An electrophoretic study showed a changing pattern of the isozymes HK1 and HK2 with increasing cell age. HK2 declines very rapidly in the early fractions whereas HK1 appears to decay more gradually.
Clin Chim Acta 1975 Dec 15
PMID:An examination of the age-related patterns of decay of the hexokinases of human red cells. 120 20

An electrophoretic system which gives a clear separation of human hexokinases HK1, HK2 and HK3 is described. The distribution of the hexokinase isozymes in various human tissues, both adult and fetal, is reported. Some properties of the isozymes were investigated. HK2 was found to be more thermolabile than HK1, and there was also a small but significant difference in molecular size. Unlike HK3, HK1 and HK2 are not inhibited by high glucose concentrations. Screening of red cell lysates from 800 unrelated European individuals revealed no genetic variants of HK1 and HK2. However, in view of their difference in properties, it seems probable that the HK1 and HK2 isozymes are determined by separate gene loci.
Biochem Genet 1975 Dec
PMID:An electrophoretic study of the distribution and properties of human hexokinases. 123 74

A practical biosensor system has been developed for the determination of urinary glucose using a flow-injection analysis (FIA) amperometric detector and ion-exchange chromatography. Glucose oxidase was immobilized onto porous aminopropyl glass beads via glutaraldehyde activation to form an immobilized enzyme column. On the basis of its negative charge at pH 5.5, endogenous urate in urine samples was effectively retained by an upstream anion-exchange resin column. The biosensor system possessed a sensitivity of 160 +/- 2.4 RU microM-1 (RU or relative unit is defined as 2.86 microV at the detection output) for glucose with a minimum detection level of 10 microM. When applied for the determination of urinary glucose, the result obtained compared very well with that of the widely accepted hexokinase assay. The immobilized glucose oxidase could be reused for more than 1000 repeated analyses without losing its original activity. The reuse of the acetate anion-exchange column before replacement would be about 25-30 analyses. Acetaminophen and ascorbic acid were also effectively adsorbed by the acetate anion exchanger. The introduction of this type of anion exchanger thus greatly improved the selectivity of the FIA biosensor system and fostered its applicability for the determination of glucose in urine samples.
Appl Biochem Biotechnol 1992 Dec
PMID:Determination of urinary glucose by a flow injection analysis amperometric biosensor and ion-exchange chromatography. 130 63

Intracellular recordings were made from neurons in the dorsolateral septal nucleus (DLSN) of rat brain slices. Lowering the concentration of extracellular glucose resulted in a concentration-dependent membrane hyperpolarization associated with a cessation of spontaneous firing. The amplitude of the excitatory postsynaptic potential (EPSP), inhibitory postsynaptic potential (IPSP), and late hyperpolarizing potential (LHP) evoked by a single stimulus applied to the fimbrial/fornix pathway was decreased when the concentration of glucose was reduced to 0-2 mM. Substitution of glucose with 2-deoxy-D-glucose (11 mM), an antimetabolite of glucose substrate, mimicked the effects of glucose depletion. Mannoheptulose (10-20 mM), a potent hexokinase blocker, and dinitrophenol (50 microM), a potent inhibitor of oxidative phosphorylation, produced both the hyperpolarization and inhibition of postsynaptic potentials, even in the presence of 11 mM glucose. The sulphonylureas, glibenclamide (10 microM) and tolbutamide (1 mM), did not antagonize the hyperpolarization and the inhibition of the postsynaptic potentials produced by glucose depletion. The amplitude of membrane depolarizations produced by pressure application of glutamate (10 mM) and the membrane hyperpolarizations produced by pressure application of either muscimol (1 mM) or baclofen (1 mM) were almost unchanged, even when glucose was reduced to 1-2 mM. These results indicate that intracellular glucose metabolism regulates the function of septal neurons, not only by changing the resting membrane potential, but also by presynaptically affecting neurotransmission between the hippocampal formation and the lateral septum.
Synapse 1992 Dec
PMID:Glucose regulation of synaptic transmission in the dorsolateral septal nucleus of the rat. 133 80

In this study, glucose repression in Saccharomyces cerevisiae was analysed under defined physiological conditions, at both the molecular and physiological levels, by pulsing glucose to a galactose-limited continuous culture. During this pulse of glucose, the galactose feed was kept constant. Directly after the glucose pulse, carbon dioxide production increased while oxygen consumption remained constant, demonstrating that the surplus of glucose had been consumed by means of fermentation. The direct accumulation of galactose in the medium after the glucose pulse indicated that the consumption of galactose had been stopped instantaneously. Galactose uptake experiments revealed that the galactose transporter was still present but apparently was incapable of galactose uptake, which could be due to inhibition of the galactose transporter by glucose. The total concentration of cAMP increased from 5 nmol g-1 at t = 0 to 25 nmol g-1 at t = 1.5 min. After 2 min the concentration of cAMP gradually decreased again to the normal level. Within 2 min after the addition of glucose, the transcription of the GAL genes and SUC2 was inhibited. In addition, the transcription of the HXK1 gene, encoding hexokinase isoenzyme 1, was also inhibited, which demonstrates that the HXK1 gene is regulated at the transcriptional level comparable with invertase.
Yeast 1992 Dec
PMID:Analysis of glucose repression in Saccharomyces cerevisiae by pulsing glucose to a galactose-limited continuous culture. 133 40

The effects of various concentrations of deoxyglucose (DG) on the aerobic metabolism of glucose in glucose-grown repressed Saccharomyces cerevisiae cells were studied at 30 degrees C in a standard pyrophosphate medium containing 4.5 10(7) cells/ml. 31P-nuclear magnetic resonance (NMR) spectroscopy was used to monitor DG phosphorylation and the formation of polyphosphates. The production of soluble metabolites of glucose was evaluated by 13C- and 1H-NMR and biochemical techniques. The cells were aerobically incubated with 25 mM of glucose and various concentrations of DG (0, 5 and 10 mM) in order to determine the DG concentration leading to optimum of 2-deoxy-D-glucose 6-phosphate (DG6P) formation without over-inhibiting the synthesis of other metabolites. The production of DG6P increased by about 25% when the external DG concentration was doubled (from 5 to 10 mM). The formation of polyphosphates (polyP), on the other hand, was found to be mainly conditioned by the DG concentration. The amount of polyP decreased by a factor of four upon addition of 5 mM DG and became undetectable in the presence of 10 mM DG. The glucose consumption and the production of soluble metabolites of [1-13C]glucose were then evaluated as a function of time in both the absence and presence of 5 mM DG. The effect of DG is to decrease the glucose consumption and the formation of polyphosphates, ethanol, glycerol, trehalose, glutamate, aspartate and succinate while stimulating the formation of arginine and citrate. Upon co-addition of 25 mM glucose and 5 mM DG, the ratio between the initial rates of glucose consumption (0.16 mM/min) and DG6P production (0.027 mM/min) is about (5.9 +/- 1.2), not very different from the ratio of the initial concentration of glucose and DG (= 5.0). Therefore, hexokinase can phosphorylate deoxyglucose as well as glucose. However, after 100 min of incubation, the glucose concentration in the external medium decreased by about 64% while only 10% of DG was phosphorylated. DG6P was formed and quickly reached the limiting value about 30 min after co-addition of glucose and DG. Nevertheless, when the maximum quantity of DG6P was obtained, the DG consumption became negligible. By contrast, the glucose consumption and the production of ethanol and glycerol, although substantially reduced by about 42%, varied linearly with time up to 80 min of incubation. Thus even in the presence of an excess of DG, glycolysis is only slowed but not gradually or completely inhibited by DG.(ABSTRACT TRUNCATED AT 400 WORDS)
Biochimie 1992 Dec
PMID:Effects of 2-deoxy-D-glucose on the glucose metabolism in Saccharomyces cerevisiae studied by multinuclear-NMR spectroscopy and biochemical methods. 136 73


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