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)

Common carp (Cyprinus carpio L.), 1 kg body weight, were acclimated for 1-2 months to water temperatures of either 7-8 degrees C (cold-acclimated group) or 23-24 degrees C (warm-acclimated group). Single fast fibres and small bundles of slow fibres were isolated from the myotomal muscles and chemically skinned. Force-velocity (P-V) characteristics were determined at 7 degrees C and 23 degrees C. The contractile properties of carp muscle fibres are dependent on acclimation temperature. In the warm-acclimated group maximum isometric tensions (P0, kN m-2) are 47 +/- 6 and 64 +/- 5 for slow muscle fibres and 76 +/- 10 and 209 +/- 21 for fast muscle fibres at 7 degrees C and 23 degrees C, respectively. Maximum contraction velocities (Vmax, muscle lengths-1), are 0.4 +/- 0.05 and 1.5 +/- 0.1 at 7 degrees C (slow fibres) and 0.6 +/- 0.04 and 1.9 +/- 0.4 at 23 degrees C (fast fibres). All values represent mean +/- S.E. P0 and Vmax at 7 degrees C are around 1.5-2.0 times higher for slow and fast muscle fibres isolated from the cold-acclimated group. Fibres from 7 degrees C-acclimated carp fail to relax completely following maximal activations at 23 degrees C. The resulting Ca-insensitive force component (50-70% P0) is associated with the development of abnormal crossbridge linkages and very slow contraction velocities. Activities of enzymes associated with energy metabolism were determined at a common temperature of 15 degrees C. Marker enzymes of the electron transport system (cytochrome oxidase), citric acid cycle (citrate synthase), fatty acid metabolism (carnitine palmitoyl transferase, beta-hydroxyacyl CoA dehydrogenase) and aerobic glucose utilization (hexokinase) have 30-60% higher activities in slow muscle from cold-acclimated than from warm-acclimated fish. Activities of cytochrome oxidase and citrate synthase in fast muscle are also elevated following acclimation to low temperature. It is concluded that thermal compensation of mechanical power output by carp skeletal muscle is matched by a concomitant increase in the potential to supply aerobically-generated ATP at low temperatures.
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PMID:Force-velocity characteristics and metabolism of carp muscle fibres following temperature acclimation. 409 57

1. Superovulated rat ovary slices from rats treated with 20mug. of luteininzing hormone/100g. body wt. 2hr. before death and from control animals have been incubated in vitro. Output of Delta(4)-3-oxo steroids (0.2mumole/g. wet wt./hr. in control tissue) was linear for 4hr., and was increased by approx. 70% in slices from luteinizing hormone-treated rats. Rate of oxygen consumption (90.0+/-4.6mumoles/g. wet wt./hr.) was linear for 3hr. and unaltered by luteinizing hormone treatment or addition of glucose (1mg./ml.) to the medium. 2. In slices from control animals, steady-state rate of glucose uptake was 78.0+/-2.9mug. atoms of carbon/g. wet wt./hr.; steady-state rates of lactate output, pyruvate output and incorporation of [U-(14)C]-glucose carbon atoms into carbon dioxide and total lipid extract were 60.7+/-0.9, 2.4+/-0.1, 18.0+/-1.1 and 0.7+/-0.1mug. atom of carbon/g. wet wt./hr. and accounted for 104.5+/-1.9% of the glucose uptake. In slices from luteinizing hormone-treated rats, glucose uptake and outputs of lactate, pyruvate and [(14)C]carbon dioxide were increased by approx. 25%, and 108.4+/-3.2% of the glucose uptake could be accounted for. 3. The total lipid extract was separated by thin-layer chromatography and saponification. Of the (14)C incorporated into this fraction during incubation with [U-(14)C]glucose 97% was found in the fractions containing glyceride glycerol and less than 3% in the fractions containing sterols, steroids or fatty acids. Appreciable quantities of (14)C were incorporated into these lipid fractions from [1-(14)C]acetate. 4. From a consideration of the tissue glycogen content, the specific activities of [(14)C]lactate and glucose 6-phosphate (C-1) derived from [1-(14)C]-, [6-(14)C]- and [U-(14)C]-glucose, and the ratio of [(14)C]carbon dioxide yields from [1-(14)C]glucose and [6-(14)C]glucose, it was concluded that there was no appreciable glycogenolysis or flow through the pentose phosphate cycle. 5. In ovary slices from both control and luteinizing hormone-treated animals, glucose in vitro raised the incorporation rate of (14)C from [1-(14)C]acetate into sterols and steroids. Luteinizing hormone in vivo stimulated the incorporation rate in vitro but only in the presence of glucose. 6. In slices incubated in medium containing [(3)H]water, [(14)C]sorbitol and glucose (1mg./ml.), the total water space (865+/-7.1mul./g.) and the extracellular water space (581+/-22mul./g.) were unchanged by luteinizing hormone treatment in vivo but the glucose space was raised from 540+/-23.6mul./g. to 639+/-31.3mul./g. 7. Luteinizing hormone treatment was found to lower the tissue concentration of the hexose monophosphates and to increase the total activity of hexokinase, glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase and possibly of phosphofructokinase. 8. The kinetic properties of a partially purified preparation of phosphofructokinase were found to be qualitatively similar to those from other mammalian tissues. 9. The results are discussed with reference to both the role of glucose metabolism in steroidogenesis and the mechanism by which luteinizing hormone increases the rate of glucose uptake.
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PMID:Glucose metabolism in the superovulated rat ovary in vitro. Effects of luteinizing hormone and the role of glucose metabolism in steroidogenesis. 424 Jul 7

Exposure of red cells to fluoride produces a variety of metabolic alterations, most of which are based upon the secondary effects of enolase inhibition, which reduces pyruvate synthesis and interferes with the regeneration of diphosphopyridine nucleotide (NAD). Adenosine triphosphate (ATP) is consumed in the hexokinase and phosphofructokinase reactions but is not regenerated since the deficiency of NAD limits glyceraldehyde phosphate dehydrogenase. ATP depletion in the presence of fluoride and calcium induces a massive loss of cations and water. Of the other known sites of ATP utilization, membrane-bound ATPase is inhibited by fluoride, but the incorporation of fatty acids into membrane phospholipids is unaffected until ATP is depleted. The addition of methylene blue to fluoride-treated red cells regenerates NAD, permitting triose oxidation and the generation of 3-phosphoglycerate and 2,3-diphosphoglycerate. Enolase inhibition is then partially overcome by mass action, and sufficient glycolysis proceeds to maintain the concentration of ATP. This in turn prevents the massive cation and water loss, and permits membrane phospholipid renewal to proceed. Membrane ATPase activity is not restored by the oxidant so that normal cation leakage remains unopposed by cation pumping in red cells exposed to the combination of fluoride and methylene blue.
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PMID:Energy metabolism in human erythrocytes. I. Effects of sodium fluoride. 432 3

Analyses of key glycolytic intermediates in freshly drawn red cells from six related individuals suggest that decreased hexokinase activity underlies the hemolytic process in the two members with overt hemolysis. Low red cell glucose 6-phosphate (G6P) was observed not only in the anemic patients but in the presumptive heterozygotes as well and served as a useful marker for the presence of the trait. Hexokinase activity was labile in distilled water hemolysates but was only slightly low when protected by glucose, mercaptoethanol, and ethylenediaminetetraacetate (EDTA). Normal red cell hexokinase was demonstrated to be dependent on glucose for maintenance of activity after heating to 45 degrees C. The cells of the proposita are unable to utilize glucose efficiently at glucose concentrations lower than 0.2 mmole/liter whereas normal cells maintain linear glucose consumption to at least 0.05 mM glucose. These qualitative abnormalities could result from the presence of a mutant hexokinase with an abnormally reactive sulfhydryl group and altered substrate affinity in the red cells of this kindred.
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PMID:Hemolytic anemia with impaired hexokinase activity. 498 Sep 29

1-10 muM ATP stimulated H(+) uptake and slowed the release of H(+) in the dark in chloroplasts illuminated at pH values at which photophosphorylation can occur, but not at pH 6.5. This ATP stimulation of H(+) uptake was abolished by an antiserum to the chloroplast coupling factor and was reduced by the energy transfer inhibitors phlorizin and Dio-9. ATP synthesis after illumination was also enhanced by ATP. Electron flow from water to methyl viologen was inhibited by the same low concentrations of ATP.ADP also increased the extent of H(+) uptake in chloroplasts, even in the presence of arsenate and MgCl(2). In the presence of hexokinase and glucose, as well as arsenate and Mg(++), ADP inhibited H(+) uptake. The failure of previous investigators to observe a direct inhibition of H(+) uptake by phosphorylation was probably caused by a masking of the inhibition by the stimulation of H(+) uptake by ATP. Furthermore, the stimulation of H(+) uptake by ATP provides an explanation for its inhibition of electron flow.
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PMID:Effects of adenine nucleotides on hydrogen-ion transport in chloroplasts. 528 86

Rats preferring ethanol were distinct from water-consuming animals in a decreased level of immunoreactive insulin im blood serum as well as in glucokinase activity of liver tissue. Per oral loading with glucose, 4 g/kg of body mass, enabled to detect a difference in the sugar phosphorylation via hexokinase and glucokinase reactions as well as the dissimilar sensitivity of the insulin system to glucose in the ethanol-, water-consuming and intermediate animals. Ethanol-consuming rats were more resistant to the effect of starvation during 48 hrs. The data obtained suggest that the characteristic properties of glucose metabolism in ethanol-consuming rats appear to be responsible for increased consumption of ethanol, which is used as optimal energy source, metabolized via pathways which did not involve the glycolytic pathway.
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PMID:[Characteristics of glucose metabolism in rats with different preferences for alcohol]. 609 27

Aldehyde analogues of the normal alcohol substrates induce ATPase activities by glycerokinase (D-glyceraldehyde), fructose-6-phosphate kinase (2,5-anhydromannose 6-phosphate), fructokinase (2,5-anhydromannose or 2,5-anhydrotalose), hexokinase (D-gluco-hexodialdose), choline kinase (betaine aldehyde), and pyruvate kinase (glyoxylate). Since purified deuterated aldehydes give V and V/K isotope effects near 1.0 for glycerokinase, fructokinase with 2,5-anhydro[1-2H]talose, hexokinase, choline kinase, and pyruvate kinase, the hydrates of these almost fully hydrated aldehydes are the activators of the ATPase reactions. Fructose-6-phosphate kinase and fructokinase with 2,5-anhydro[1-2H]mannose show V/K deuterium isotope effects of 1.10 and 1.22, respectively, suggesting either that both hydrate and free aldehyde may be activators (predicted values are 1.37 if only the free aldehyde activates the ATPase) or, more likely, that the phosphorylated hydrate breaks down in a rate-limiting step on the enzyme while MgADP is still present and the back-reaction to yield free hydrate in solution is still possible. 18O was transferred from the aldehyde hydrate to phosphate during the ATPase reactions of glycerokinase, fructose-6-phosphate kinase, fructokinase, and hexokinase but not with choline kinase or pyruvate kinase. Thus, direct phosphorylation of the hydrates by the first four enzymes gives the phosphate adduct of the aldehyde, which decomposes nonenzymatically, while with choline kinase and pyruvate kinase the hydrates induce transfer to water (metal-bound hydroxide or water with pyruvate kinase on the basis of pH profiles). Observation of a lag in the release of phosphate from the glycerokinase ATPase reaction at 15 degrees C supports the existence of a phosphorylated hydrate intermediate with a rate constant for breakdown of 0.035-0.043 s-1 at this temperature. Kinases that phosphorylate creatine, 3-phosphoglycerate, and acetate did not exhibit ATPase activities in the presence of keto or aldehyde analogues (N-methylhydantoic acid, D-glyceraldehyde 3-phosphate, and acetaldehyde, respectively), possibly because of the absence of an acid-base catalytic group in the latter two cases. These analogues were competitive inhibitors vs. the normal substrates, and in the latter case, the hydrate of acetaldehyde was shown to be the inhibitory species on the basis of the deuterium isotope effect on the inhibition constant.
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PMID:Mechanisms of aldehyde-induced adenosinetriphosphatase activities of kinases. 609 91

An enzymatic assay for the determination of alpha-amylase in serum was developed which employed a soluble substrate, maltoheptaose, and a coupled enzymatic indicator reaction consisting of alpha-glucosidase and the hexokinase-glucose-6-phosphate dehydrogenase system. We used high-performance liquid chromatography (HPLC) to establish the action pattern of maltoheptaose under the test conditions: (A) the action pattern of alpha-amylase, (B) that of the combined action of alpha-amylase and alpha-glucosidase. Conductive to this effect was: the availability of pure maltoheptaose and human pancreatic alpha-amylase; the development of an adequate procedure for sample pretreatment (partition chromatography on a mixed-bed ion exchange) and of an HPLC system for separation of substrate and reaction products without interference from by products of the assay (partition chromatography on a cation-exchange column with acetonitrile-water); and the use of a new, very sensitive refractometric detector revealing sugar amounts as low as 40 ng. We derived the following stoichiometric equations: (see formula index).
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PMID:Action pattern of human pancreatic alpha-amylase on maltoheptaose, a substrate for determining alpha-amylase in serum. 616 29

A method is described for the determination of the pH of intracellular water based on the distribution of [14C]benzoate (0.01 mM) between intra- and extra-cellular water. Benzoate at higher concentrations (2-10mM) enters the yeast cell in the undissociated form, and its neutralization within the cell can cause a shift of the pH of the intracellular water by more than 1 pH unit. Benzoate causes an accumulation of the two hexose monophosphates of yeast glucose fermentation and a decrease in intermediates beyond phosphofructokinase, suggesting inhibition at this stage. Benzoate also causes a concomitant fall in [ATP]. Phosphofructokinase is inhibited to a greater extent than hexokinase at acid pH. There is a relationship between intracellular pH, phosphofructokinase inhibition and CO2 production, suggesting that the antifungal action of benzoate is caused by an accumulation of benzoate at low external pH, which lowers the intracellular pH into the range where phosphofructokinase is sensitive. The subsequent inhibition of glycolysis causes a fall in [ATP] and thus restricts growth.
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PMID:Studies on the mechanism of the antifungal action of benzoate. 622 83

Measurements of the fluorescent lifetimes of the rare earth metal Eu3+ in varying mole fractions of H2O/D2O were used to determine the hydration of the metal in the presence of ATP and/or hexokinase or chloroplast reversible ATPase. The number of water molecules coordinated to the metal in Eu3+-ATP was estimated to be 2.6; when this complex is bound to hexokinase, 1 water molecule is displaced. Upon binding to chloroplast reversible ATPase, the metal coordinates 1 water molecule while the Eu3+-ATP complex does not retain any associated solvent. These numbers are in contrast to the 9 solvent molecules coordinated to the naked metal ion. These results are discussed in reference to mechanistic and structural considerations of the two enzymes.
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PMID:Fluorescence decay time measurements of Eu3+-ATP-enzyme complexes. Replacement of the metal hydration water by active site ligands. 622 53


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