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)

In the process of defining the recruitment of fuel and pathway selection in rainbow trout fast-twitch white skeletal muscle, it was clear that the near-maximal myosin adenosinetriphosphatase activity during a 10-s sprint was supported solely by phosphocreatine hydrolysis. A conservative estimate of the ATP turnover was 188 mumol X g wet wt-1 X min-1. It was not until the rate and force of contraction decreased that the relative contribution of anaerobic glycogenolysis became increasingly important. Over a 10-min period of burst swimming at approximately 120% of maximum aerobic steady-state swimming velocity of trout determined in a Brett-type swim tunnel, fatigue was associated with the near-depletion of glycogen in white muscle. The ATP turnover supported by anaerobic glycogenolysis was 78 mumol X g wet wt-1 X min-1. The glycolytic pathway appeared functional at this time with control sites being identified at hexokinase and phosphofructokinase (PFK-1). PFK-1 did not appear to be inhibited by low muscle pH (pH 6.66). In another exercise protocol lasting 30 min, complete exhaustion was related to glycogen depletion. The sum of all glycolytic intermediates from glucose 6-phosphate to pyruvate at exhaustion decreased by a dramatic 80% compared with the 25% decrease for the 10-min fatigue swimming protocol. This large depletion of glycolytic intermediates was accompanied by an 80% fall in ATP, a 70-80% reduction in the ATP/ADP and phosphorylation potential, and a 2.5-fold increase in the NAD/NADH. Associated with these changes was a marked displacement of the phosphoglycerate kinase (PGK), and the combined glyceraldehyde-3-phosphate dehydrogenase-PGK reactions from thermodynamic equilibrium. As a general conclusion, fatigue and exhaustion should be viewed as a multicomponent biochemical process in response to low glycogen and not leveled at one particular step of the glycolytic pathway.
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PMID:Regulation of anaerobic ATP-generating pathways in trout fast-twitch skeletal muscle. 360 83

It is shown in experiments on rats that the early postischemic period after 1- and 1.5-hour ischemia of kidneys is characterized by a decrease in the damage of the glycolytic system site which induces glucose-6-phosphate transformation into lactate and by an increase in the inhibition intensity of the initial hexokinase reaction of glycolysis. In the postischemic period after more prolonged (2-, 3-hour) ischemia the damage of the glycolytic system develops also at the site of glucose-6-phosphate transformation into lactate. Administration either of the nucleotide complex (NAD and AMP) or calmodulin inhibitors (aminazine and zinc sulphate) to rats prior to two-hour occlusion of kidneys vessels promotes a decrease in the inhibition of the glycolytic system activity in the postischemic period. At the same time the separate and combined application of zinc sulphate and triftazin (the most intensive calmodulin inhibitor) is not efficient. The positive effect of NAD, AMP and aminazine on the state of the glycolytic kidney system in the postischemic period correlates with the improvement of the blood microcirculation processes in them.
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PMID:[Glycolysis in the rat kidney shortly after ischemia and administration of calmodulin inhibitors, AMP and NAD]. 379 79

M. Kuwajima, C. B. Newgard, D. W. Foster, and J. D. McGarry (1986, J. Biol. Chem. 261, 8849-8853) have concluded that the reason postprandial hepatic glycogenesis occurs primarily from gluconeogenic precursors rather than glucose is because glucokinase activity is insufficient to support the observed rates of glycogen synthesis. F. L. Alvares and R. C. Nordlie (1977, J. Biol. Chem. 252, 8404-8414) have concluded that the combined activities of glucokinase and hexokinase are less than the apparent rates of hepatic glucose uptake. We have identified several factors in the assays used in these studies which lead to substantial underestimations of glucokinase activity. Glucokinase was assayed either by allowing glucose 6-phosphate to accumulate over 10 min (discontinuous assay) or by coupling the formation of glucose 6-phosphate with its oxidation by Leuconostoc mesenteroides glucose 6-phosphate dehydrogenase and NAD (continuous assay). Accurate determinations of glucokinase at 37 degrees C with subsaturating glucose require both 100 mM KCl and 2.5 mM dithioerythritol in the assay medium; 2-mercaptoethanol will not substitute for dithioerythritol. When both KCl and dithioerythritol are absent (Kuwajima et al.) glucokinase activity is underestimated by 3- to 5-fold. The discontinuous assay as used previously (Alvares and Nordlie) underestimates glucokinase activity in crude extracts by 2- to 2.5-fold, due in part to the hydrolysis of glucose 6-phosphate and its transformation to other hexose monophosphates. Under optimized conditions at 37 degrees C both assays yield similar results in extracts from fed rats, i.e., 2-3 and 4-5 units/g liver at 10 and 100 mM glucose, respectively. Some implications of the finding that total hepatic glucose phosphorylating capacity at physiological concentrations significantly exceeds the observed rates of postprandial glycogen synthesis are discussed.
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PMID:Factors underlying significant underestimations of glucokinase activity in crude liver extracts: physiological implications of higher cellular activity. 381 60

Lonidamine is a potent inhibitor of spermatogenesis and a hyperthermic sensitizer. The principal established locus of biochemical action of lonidamine is a selective inhibitory effect of the energy metabolism either in NAD-linked reactions in germ cell mitochondria, as well as the glycolytic metabolism of a variety of tumor cell lines by means of inhibition of mitochondrially bound hexokinase. We carried out in vivo tumor experiments to determine whether lonidamine when combined with radiation could potentiate the cytotoxic effects of radiation on two murine tumors. The combined effects of single acute lonidamine (100 mg/kg) and single dose X-irradiation were evaluated on the transplanted methylcholanthrene-induced fibrosarcoma in BALB/c mice and on the radiation-induced fibrosarcoma in C3H/He mice. The radiosensitizing effect by lonidamine was maximal when lonidamine was administered immediately prior to or after X-irradiation. The dose modifying factor of lonidamine is estimated to be 1.36 for methylcholanthrene-induced fibrosarcoma tumors and 1.25 for radiation-induced fibrosarcoma tumors. There was no disproportionately enhanced skin reaction following the combined treatments. The present results of the potentiating effects of radiation may be attributed, in part, to the findings of cell culture studies that lonidamine is a potent inhibitor of repair of potentially lethal damage.
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PMID:Potentiation of radiation effects on two murine tumors by lonidamine. 394 89

Metabolic activity of erythrocytes was studied in healthy pregnant women. The second half of the normal pregnancy was characterized by an increase in activity of hexokinase, in content of 2,3-DPG, ADP, by a distinct decrease in ATP, NAD and the ratio ATP/ADP as well as by unaltered ratios NAD/NADH and lactate/pyruvate.
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PMID:[Glycolytic enzyme activity and levels of glycolysis metabolites in erythrocytes in physiological pregnancy]. 400 52

The metabolic properties of mitochondria from rat cerebral cortex and olfactory bulb were investigated. The pyruvate-supported oxygen uptake rates by olfactory bulb mitochondria were significantly lower than those by cerebrocortical mitochondria. This is consistent with the differences in pyruvate dehydrogenase complex activities between these mitochondrial preparations. Pyruvate dehydrogenase kinase, NAD-linked isocitrate dehydrogenase, and hexokinase activities in olfactory bulb mitochondria were significantly lower than those in cerebrocortical mitochondria. However, NADP-linked isocitrate dehydrogenase, and NAD-linked and NADP-linked glutamate dehydrogenase activities in olfactory bulb mitochondria were significantly higher than those in cerebrocortical mitochondria. The differences between these two mitochondrial preparations in terms of the activities of these energy-metabolizing enzymes reflect the differences detected in the homogenates of these regions.
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PMID:Differences in some of the metabolic properties of mitochondria isolated from cerebral cortex and olfactory bulb of the rat. 404 57

1. Enzymic evidence supporting the operation of the Entner-Doudoroff pathway in the anaerobic conversion of glucose into ethanol and carbon dioxide by Zymomonas mobilis is presented. 2. Cell extracts catalysed the formation of equimolar amounts of pyruvate and glyceraldehyde 3-phosphate from 6-phosphogluconate. Evidence that 3-deoxy-2-oxo-6-phosphogluconate is an intermediate in this conversion was obtained. 3. Cell extracts of the organism contained the following enzymes: glucose 6-phosphate dehydrogenase (active with NAD and NADP), ethanol dehydrogenase (active with NAD), glyceraldehyde 3-phosphate dehydrogenase (active with NAD), hexokinase, gluconokinase, glucose dehydrogenase and pyruvate decarboxylase. Extracts also catalysed the overall conversion of glycerate 3-phosphate into pyruvate in the presence of ADP. 4. Gluconate dehydrogenase, fructose 1,6-diphosphate aldolase and NAD-NADP transhydrogenase were not detected. 5. It is suggested that NAD is the physiological electron carrier in the balanced oxidation-reduction involved in ethanol formation.
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PMID:The route of ethanol formation in Zymomonas mobilis. 428 42

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

The enzyme activities involved in fructose metabolism were measured in samples of human liver. On the basis of U/g of wet-weight the following results were found: ketohexokinase, 1.23; aldolase (substrate, fructose-1-phosphate), 2.08; aldolase (substrate, fructose-1,6-diphosphate), 3.46; triokinase, 2.07; aldehyde dehydrogenase (substrate, D-glyceraldehyde), 1.04; D-glycerate kinase, 0.13; alcohol dehydrogenase (nicotinamide adenine dinucleotide [NAD]) substrate, D-glyceraldehyde), 3.1; alcohol dehydrogenase (nicotinamide adenine dinucleotide phosphate [NADP]) (substrate, D-glyceraldehyde), 3.6; and glycerol kinase, 0.62. Sorbitol dehydrogenases (25.0 U/g), hexosediphosphatase (4.06 U/g), hexokinase (0.23 U/g), and glucokinase (0.08 U/g) were also measured. Comparing these results with those of the rat liver it becomes clear that the activities of alcohol dehydrogenases (NAD and NADP) in rat liver are higher than those in human liver, and that the values of ketohexokinase, sorbitol dehydrogenases, and hexosediphosphatase in human liver are lower than those values found in rat liver. Human liver contains only traces of glycerate kinase. The rate of fructose uptake from the blood, as described by other investigators, can be based on the activity of ketohexokinase reported in the present paper. In human liver, ketohexokinase is present in a four-fold activity of glucokinase and hexokinase. This result may explain the well-known fact that fructose is metabolized faster than glucose.
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PMID:Enzymes of fructose metabolism in human liver. 438 49

1. The activities of six enzymes (hexokinase, phosphoglucose isomerase, phosphofructokinase, aldolase, glucose 6-phosphate dehydrogenase and amylase) in extracts of pea cotyledons were determined. The activities during the first 10 days after germination showed individual and characteristic changes that indicate a specific control of both synthesis and destruction of enzymes. 2. Tissue contents of glucose, inorganic phosphate, glucose 6-phosphate, fructose 6-phosphate, ATP, ADP, AMP, NAD and NADP were also determined, and a correlation is reported between the substrate concentrations at day 1 and the subsequent enzymic activity. 3. The initial NAD(+)/NADH ratio value of 1 changed to about 3 by day 4; the NADP content was lower and changes in the oxidation state were less striking. The ratio of ATP to ADP and AMP remained virtually constant.
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PMID:Correlated changes of some enzyme activities and cofactor and substrate contents of pea cotyledon tissue during germination. 438 39


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