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)

Effects of glucose concentration and anoxia upon the metabolite concentrations and rates of glycolysis and respiration have been investigated in the perfused liver of the fetal guinea pig. In most cases the metabolite concentrations in the perfused liver were similar to those observed in vivo. Between 50 days and term there was a fall in the respiratory rate and in the concentration of ATP and fructose 1,6-diphosphate and an increase in the concentration of glutamate, glycogen and glucose. Reducing the medium glucose concentration from 10 mM to 1 mM or 0.1 mM depressed lactate production and the concentration of most of the phosphorylated intermediates (except 6-phosphogluconate) in the liver of the 50-day fetus. This indicates a fall in glycolytic rate which is not in accord with the known kinetic properties of hexokinase in the fetal liver. Anoxia increased lactate production by, and the concentrations of, the hexose phosphates ADP and AMP in the 50-day to term fetal liver, while the concentration of ribulose 5-phosphate, ATP and some triose phosphates fell. These results are consistent with an activation of glycolysis, particularly at phosphofructokinase and of a reduction in pentose phosphate pathway activity, particularly at 6-phosphogluconate dehydrogenase. The calculated cytosolic NAD+/NADH ratio for the perfused liver was similar to that measured in vivo and evidence is presented to suggest that the dihydroxyacetone phosphate/glycerol 3-phosphate ratio gives a better indication of cytosolic redox than the lactate/pyruvate ratio. The present observations indicate that phosphofructokinase hexokinase and possibly pyruvate kinase control the glycolytic rate and that glyceraldehyde-3-phosphate dehydrogenase is at equilibrium in the perfused liver of the fetal guinea pig.
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PMID:Some effects of glucose concentration and anoxia on glycolysis and metabolite concentrations in the perfused liver of fetal guinea pig. 2 74

The behavior of enzyme activities, substrates and metabolites of glycosis as well as of the pentose phosphate shunt following local irradiation (250 to 6000 R surface dose) is biochemically investigated in the guinea-pig's myocardium. During irradiation, an activation of phosphorylase-a is going on while the total phosphorylase content remains unchanged. Enzyme activities of hexokinase and phosphofructokinase are increased in dependence on dosage as well as time. The glycogen content is being reduced; tissular concentration of the metabolites glucose-1-phosphate, glucose-6-phosphate, glyceraldehyde-3-phosphate, glycerol-3-phosphate, and pyruvate increases following irradiation; the content of fructose-1,6-diphosphate, dihydroxyacetonephosphate, and lactate is decreased. The activity of glucose-6-phosphate dehydrogenas is slightly inhibited, whereas 6-phosphogluconate-dehydrogenase remains unaffected.
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PMID:[Studies on the effect of radiation on electrolyte changes and metabolism of the myocardium. V. Changes in enzyme activities and glycolysis metabloites due to radiation]. 12 7

The purpose of the present investigation was to shed some light on the suppression of the glycolytic pathway by anesthetics. The antimetabolite 6-aminonicotinamide (6-AN) was used to discriminate between the key enzymes hexokinase and phosphofructokinase which are suggested to be involved in the effect of anesthetics on glycolysis. The cerebral energy metabolism was studied in the isolated perfused rat brain after the addition of thiopental (0.15 mM) to the perfusion medium, after the administration of 6-AN (35mg/kg i.p.) to the intact animals 15 h before perfusion was started, as well as in brain preparations treated in the same manner with both 6-AN and thiopental. After a perfusion period of 30 min brain levels of the following substrates and metabolites were determined: phosphocreatine, ATP, ADP, AMP, glycogen, glucose, glucose 6-phosphate, fructose 6-phosphate, pyruvate, lactate, alpha-ketoglutarate, blutamate, ammonia, and 6-phosphogluconate. The metabolic alterations in the isolated rat brain caused by 6-AN or thiopental were such as reported in the literature. When the isolated brains of the 6-AN pretreated rats were perfused with thiopental we found as the most interesting result that the concentration of glucose 6-phosphate was reduced in comparison to that in brains only treated with 6-AN but still significantly higher than that in controls. The glucose concentration was significantly elevated and the lactate concentration decreased considerably. The effect of thiopental on cerebral glycolysis was interpreted as an inhibition of hexokinase activity.
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PMID:Inhibition of glucose phosphorylation in rat brain by thiopental. 13 93

Various enzymes of glycolysis (hexokinase, phosphoglucoisomerase, aldolase and lactate dehydrogenase), the Krebs cycle (isocitrate, succinic and malate dehydrogenases), and the pentose phosphate cycle (glucose-6-phosphate and 6-phosphogluconate dehydrogenases) were studied in buffalo spermatozoa by biochemical and cytochemical methods. The enzymes of glycolysis were found to be loosely bound whereas those of the Krebs and pentose phosphate cycles were strongly bound to mitochondrial membranes. All the enzymes studied were localized histochemically in the mid-piece.
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PMID:Glycolytic, Krebs cycle and pentose phosphate cycle enzymes in spermatozoa of the buffalo (Bubalus bubalis). 51 3

The ratios of some key enzymatic activities of carbohydrate metabolism have been measured in human tumor cytosols. The activities of whole hexokinase (low Km, EC 2.7.1.1 and high Km, EC 2.7.1.2), 6-phosphogluconate dehydrogenase (EC 1.1.1.43), glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and glucose-6-phosphate isomerase (EC 5.3.1.9) change according to a biochemical pattern coherent with cell growth requirements. 6-phosphogluconate dehydrogenase activity was in each sample tested higher than glucose-6-phosphate dehydrogenase activity; this indicates that 6-phosphogluconate, a powerful inhibitor of glucose-6-phosphate isomerase, is unlikely to accumulate and inhibit this enzyme and glucose-6-phosphate channelling into glycolysis.
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PMID:6-phosphogluconate dehydrogenase, glucose-6-phosphate dehydrogenase, glucose-6-phosphate isomerase, and hexokinase activity ratios in some human tumor cytosols. 74 21

The activity of 19 enzymes (hexokinase, glucoso-6-phosphatisomerase, alpha-glycerophosphate-, lactate-, succinate-, isocitrate-, malate-, glucoso-6-phosphate-, 6-phosphogluconate-, glutamate-, alcohol-, inosine-5'-phosphate-, guanosine-5'-monophosphate-dehydrogenase, cytochromoxidase NAD.N2- and NADP.N2-diaphorase, monoaminoxidase, alkaline and acid phosphatase) was studied comparatively in the mucosa of control rats and in tumors of the small intestine (27), and large intestine (176), induced in 41 rats percutaneously by 1,2-dimethylhydrazine. A decreased level of the enzymes of tissue respiration and Krebs cycle was found with a simultaneous increase in the activity of the enzymes of glycolysis and pentoso-monophosphate shunt. These data evidence variations in tumor metabolism consisting in oxidizing phosphorylation, being replaced by aerobic glycosis, and also reflecting an intensive proliferation of tumor cells.
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PMID:[An enzymohistochemical study of experimental tumors of the intestine]. 123 60

A cyclic pathway of NADPH generation involving interconversion of mannitol and fructose has been proposed to occur in fungi. In Aspergillus nidulans three enzymes of this proposed mannitol cycle (hexokinase, NADP-mannitol dehydrogenase and mannitol-l-phosphate phosphatase) were shown to be localized exclusively in the cytosol. Two isoenzymes of the fourth enzyme (mannitol-l-phosphate dehydrogenase) were detected and shown to be localized respectively in the mitochondrion and the cytosol. The mitochondrial isoenzyme appeared to be present on the outer face of the inner mitochondrial membrane. No evidence was found for a coordinated change in the maximal activities of the enzymes of the proposed mannitol cycle in extracts prepared from mycelia grown on six different carbon, and three different nitrogen sources nor for any increase in these activities induced by growth on NO3-. Studies of this type in which other NADP-linked dehydrogenases were measured showed that for most carbon sources tested growth on NO3- increased the maximal activity of NADP-isocitrate dehydrogenase as well as that of glucose-6-phosphate and 6-phosphogluconate dehydrogenases but had little effect on the maximal activity of NADP-malate dehydrogenase (decarboxylating). Our studies provide no support for the operation of the mannitol cycle, or for the proposed role of this cycle in NADPH generation in A. nidulans.
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PMID:NADPH generation in Aspergillus nidulans: is the mannitol cycle involved? 314 71

A specific and simple enzymatic method for the determination of glycogen in tissue, with a detection limit of about 1 microgram glycogen (6.2 nmol glucosyl residues) is described. Glycogen is converted to 6-phosphogluconate by means of amyloglucosidase, hexokinase, and glucose-6-phosphate dehydrogenase. The increase in NADPH is measured fluorometrically. Muscle tissue (5-20 mg) is hydrolysed in hot KOH (5.4 mol/l), neutralized and analysed. The glycogen-glucosyl content in wet rat diaphragm muscle is about 43 mmol/kg.
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PMID:Enzymatic microanalysis of glycogen. 371 72

Essential differences are established between the activities in enzymes of monophosphohexoses' transformation in the Zajdela hepatoma and liver of tumour-bearing rats. So, a very low hexokinase activity is observed in the liver, the activity of phosphoglucomutase and glucose-6-phosphate being high. In hepatoma cells the activity of hexokinase is relatively high and that of phosphoglucomutase, glucose-6-phosphate phosphatase and dehydrogenases--glucose-6-phosphate and 6-phosphogluconate inhibiting the activity of phosphoglucomutase is considerably lower. Significant differences are also found in the ratios of the glucose, glucose-6-phosphate, fructose and fructose-6-phosphate concentrations, that evidences for changes in the regulatory mechanisms in the hepatoma cells.
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PMID:[Characteristics of hexosephosphate transformation regulation in Zajdela hepatoma and the liver of tumor-bearing rats]. 381 Aug 99

The natural product of the glucose-6-phosphate dehydrogenase reaction is 6-phosphoglucono-delta-lactone, which must be hydrolyzed to 6-phosphogluconic acid before it can be further metabolized by 6-phosphogluconate dehydrogenase. Because this lactone is very unstable, it has been uncertain whether the enzyme that hydrolyzes it, 6-phosphogluconolactonase, is required for functioning of the hexose monophosphate pathway. We have purified glucose-6-phosphate dehydrogenase, 6-phosphogluconolactonase, and 6-phosphogluconate dehydrogenase from human erythrocytes to the point where each enzyme is essentially free of each of the other activities. We constructed an artificial hexose monophosphate pathway from these enzymes, providing as substrate 14C-labeled glucose-6-phosphate either directly or by continual generation from 14C-glucose by yeast hexokinase and adenosine triphosphate. The oxidation of 6-phosphogluconic acid was estimated by measuring the CO2 formed. In the absence of a reduced nicotinamide-adenine dinucleotide phosphate (NADPH)-oxidizing system, such as oxidized glutathione (GSSG)-glutathione reductase or phenazine methosulfate, little CO2 was formed, and the presence of 6-phosphogluconolactonase did not affect the amount that was produced. When the hexose monophosphate pathway was stimulated by providing an NADPH-oxidizing system, CO2 was produced two and a half to five times as fast in the presence of 6-phosphogluconolactonase as in its absence. These studies suggest that 6-phosphogluconolactonase is required for the functioning of the hexose monophosphate pathway when the rate of oxidation of NADPH is accelerated.
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PMID:Limiting role of 6-phosphogluconolactonase in erythrocyte hexose monophosphate pathway metabolism. 393 73


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