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)

Bacterial luciferase and NADH:FMN oxidoreductase have been immobilized onto arylamine glass beads. These immobilized enzymes can detect as little as 0.2 pmol of NADH per assay sample. Glucose-6-phosphate dehydrogenase has been co-immobilized with these enzymes, and with this system it is possible to quantitate 1 pmol of glucose 6-phosphate. By co-immobilizing a fourth enzyme, hexokinase, onto the glass beads, the system can reproducibly detect 20 pmol of glucose per liter. These immobilized enzyme systems are potentially superior to soluble enzymes by being reusable and much more stable. We compared the light-emitting properties of the immobilized enzyme systems with that of an equivalent mixture of the soluble enzymes. The most striking difference was the apparently more efficient conversion of NADH or glucose 6-phosphate to light by the immobilized enzymes. We used hydroxysteroid dehydrogenase in developing a soluble coupled system for the assay of androsterone and testosterone. The lower limit of detection was 100 pmol.
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PMID:Properties and uses of immobilized light-emitting enzyme systems from Beneckea harveyi. 3 21

In order to devise a more physiologic system for measuring depletion of red cell ATP levels, the effect of incubating human erythrocytes with 2-deoxyglucose has been investigated. ATP depletion proceeds very slowly at a 20 mM concentration of 2-deoxyglucose, a level which exceeds the Km of hexokinase for this substrate by more than 10-fold. However, at 160 mM concentration of 2-deoxyglucose, ATP depletion proceeds sufficiently rapidly that nearly 90% of ATP has disappeared from the red cell after 2 1/2 hr of incubation. To explain this observation, a number of additional studies were carried out. It was found that 2-deoxyglucose penetrated rapidly into red cells. Phosphorylation of 2-deoxyglucose in red cells was inhibited by both products of the 2-deoxyglucose-phosphorylating reaction, namely, 2-deoxyglucose-6-phosphate and ADP. Inhibition of 2-deoxyglucose phosphorylation was diminished at higher-than-physiologic pH levels. Red cells may be relatively rapidly depleted of ATP by incubation with 100 mM 2-deoxyglucose in a saline-phosphate-buffered medium, pH 7.8. In such rapidly depleted cells, the morphologic changes which formerly were attributed to ATP depletion do not occur.
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PMID:Depletion of red cell ATP by incubation with 2-deoxyglucose. 3 6

1) The rate of 2,3-bisphosphoglycerate breakdown is independent of pH value. 2) The adenine nucleotide pattern at alkaline pH values with its characteristic lowering of ATP and the accompanying accumulation of fructose-1,6-bisphosphate is caused by a relative excess of the activity of the hexokinase-phosphofructokinase system as compared wity pyruvate kinase. 3) The breakdown of adenine nucleotides proceeds via AMP mainly through phosphatase and not via AMP deaminase. 4) The constancy of the sum of nucleotides as long as glucose is present is postulated to be due to resynthesis via adenosine kinase which competes successfully with adenosine deaminase. 5) A procedure is given to calculate ATPase activity of glucose-depleted red cells. The results indicate that the ATPase activity is less at lower pH values and declines with time. An ATPase with a high Km for ATP is postulated. 6) During glucose depletion ATP production is mostly derived from the breakdown of 2,3-bisphosphoglycerate and the supply from the pentose phosphate pool both of which proceed at a constant rate. The contribution of pentose phosphate from the breakdown of adenine nucleotides amounts to 40% of the lactate formed at pH 6.8 and is about twice the lactate at pH 8.1.
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PMID:The breakdown of adenine nucleotides in glucose-depleted human red cells. 4 52

The activity of enzymes regulating the processes providing functional activity of leukocytes was studied in the exudate leukocytes of healthy rabbits and animals with alloxan diabetes. Rabbits with diabetes displayed a reduction of hexokinase, phosphoglucomutase, glucose-6-phosphate dehydrogenase and adenylate kinase activity. The activity of UDPH-pyrophosphorylase, UDPH-glycogentranspherase, 6-phosphogluconate dehydrogenase and glutathion reductase showed no significant changes in the exudate leukocytes in diabetes. A reduction of hexokinase and glucose-6-phosphate dehydrogenase limiting glycolysis and the pentose-phosphate cycle, respectively, providing energy for leukocytes and important in protein metabolism of these cells, is of great significance in the reduction of functional activity of leukocytes in the inflammatory focus in diabetes.
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PMID:[Enzymatic profile of the exudate leukocytes in diabetes mellitus]. 9 55

The aluminum present as a contaminant in ATP preparations can cause strong inhibition of yeast hexokinase P-II activity at pH 7.0 or below but has little or no inhibitory effect at a pH of 7.5 or greater. The inhibition is reversed by citrate, 3-phosphoglycerate, malate, phosphate, and catecholamines, all of which have previously been described as activators of hexokinase at low pH. We suggest that these agents activate the enzyme only by virtue of their ability to coordinate with aluminum present in the assay system. The presence of aluminum is also responsible for the "negative cooperativity" observed at low pH with respect to Mg . ATP concentration--i.e., the inhibition by aluminum is uncompetitive at low Mg . ATP concentrations but becomes competitive at high Mg . ATP concentrations. The inhibition is thought to be due to formation of a complex of Al . ATP with the enzyme, with a dissociation constant (Ki) of 0.1 microM. Yeast hexokinase P-I is somewhat less sensitive to A1 than is hexokinase P-II, and yeast glucokinase is not detectably affected. The hexokinase in rat brain (type I) shows a pH-dependent inhibition by Al similar to that observed with the yeast hexokinases, whereas the rat muscle (type II) enzyme is less sensitive, suggesting a possible relationship to aluminum encephalopathy in man.
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PMID:Proton-dependent inhibition of yeast and brain hexokinases by aluminum in ATP preparations. 11 25

The R3230AC mammary adenocarcinoma was not dependent on insulin; tumor growth was equal to or greater in diabetic rats than in intact animals. However, tumor growth was reduced when daily doses of insulin were administered. Treatment with estrogen inhibited growth of the R3230AC carcinoma, either in diabetic rats or in intact animals simultaneously treated with insulin. The effects of insulin plus estrogen treatment appeared to be additive in causing inhibition of tumor growth. Tumors from diabetic rats showed few metabolic alterations as reflected by little or no changes in the activities of selected glycolytic enzymes, pyruvate kinase, phosphofructokinase, and hexokinase, nor any striking changes in the activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, representing the pentose phosphate pathway. A modest reduction in the ratio of utilization of (1-14C)glucose: (6-14C)glucose was seen in vitro by tumors from diabetic rats. It was concluded that insulin, along with estrogen and prolactin, should be considered as a hormonal factor that influences growth of this automonous, hormone-responsive adenocarcinoma.
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PMID:Influence of insulin on estrogen-induced responses in the r3230ac mammary carcinoma. 12 68

ATP and citrate, the well known inhibitors of phosphofructokinase (ATP: D-fructose 6-phosphate 1-phosphotransferase, EC 2.7.1.11), were found to inhibit the activities of the multiple forms of phosphoglucomutase (alpha-D-glucose 1,6-bisphosphate: alpha-D-glucose 1-phosphate phosphotransferase, EC 2.7.5.1) from rat muscle and adipose tissue. This inhibition could be reversed by an increase in the glucose 1,6-bisphosphate (Glc-1,6-P2) concentration. Other known activators (deinhibitors) of phosphofructokinase, viz. cyclic AMP, AMP, ADP or Pi, had no direct deinhibitory action on the ATP or citrate inhibited multiple phosphoglucomutases. Cyclic AMP and AMP, could however lead indirectly to deinhibition of the phosphoglucomutases, by activating phosphofructokinase which catalyzes the ATP-dependent phosphorylation of glucose 1-phosphate to form Glc-1,6-P2, the la-ter then released the multiple phosphoglucomutases from ATP or citrate inhibition. The Glc-1,6-P2 was also found to exert a selective inhibitory effect on hexokinase (ATP: D-hexose 6-phosphotransferase, EC 2.7.1.1) type II, the predominant form in skeletal muscle. This selective inhibition by Glc-1,6-P2 was demonstrated on the multiple hexokinases which were resolved by cellogel electrophoresis or isolated by chromatography on DEAE-cellulose. Based on the in vitro studies it is suggested that during periods of highly active epinephrine-induced glycogenolysis in muscle, the Glc-1,6-P2, produced by the cyclic AMP-stimulated reaction of phosphofructokinase with glucose 1-phosphate, will release the phosphoglucomutases from ATP or citrate inhibition, and will depress the activity of muscle type II hexokinase.
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PMID:Complementarity in the regulation of phosphoglucomutase, phosphofructokinase and hexokinase; the role of glucose 1,6-bisphosphate. 12 9

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 activity of carbohydrate metabolism certain enzymes [hexokinase (EC 2.7.1.1.), glucokinase (EC 2.7.1.2), phosphofructokinase (EC 2.7.1.11.1), glucoso-6-phosphate-dehydrogenase (EC 1.1.1.49.)] was studied in the sheep skin when adding vitamin A, sodium sulphate and insulin to the basic ration. The activity of the studied enzymes in the skin was established to be rather high and depend to a considerable extent on feeding, seasonal and hormonal factors. In summer the activity of such enzymes as glucoso-6-phosphate-dehydrogenase and glucokinase decreases, and that of hexokinase, vice versa, increases. Vitamin A alone against a background of the basic ration almost has no effect on the activity of the enzymes, with the exception of phosphofructokinase in certain periods of the experiment. More noticeable shifts in the activity of the enzymes were observed in the case when vitamin A and sodium sulphate were added to the ration of sheep, and also with the injection of insulin. In such cases in the sheep skin there occurs first of all an increase in the activity of glucokinase and glucoso-6-phosphate-dehydrogenase.
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PMID:[Activity of some carbohydrate-metabolizing enzymes in sheep skin]. 13 Jul 4

A simple mathematical model for glycolysis in erythrocytes is presented which takes into account ATP synthesis and consumption. The system is described by four ordinary differential equations. Conditions in vivo are described by a stable steady state. The model predicts correctly the metabolite concentrations found in vivo. The parameters involved are in agreement with data on the separate steps. The metabolite changes found in pyruvate kinase-deficient erythrocytes and the species variations among erythrocytes from different animals are described satisfactorily. The roles of the enzymes in the control of metabolites and glycolytic flux are expressed in the form of a control matrix and control strengths [R. Heinrich & T.A. Rapoport (1974) Eur. J. Biochem. 42, 89-95] respectively. Erythrocytes from various species are shown to be adapted to a maximal ATP-consumption rate. The calculated eigenvalues reveal the pronounced time-hierarchy of the glycolytic reactions. Owing to the slowness of the 2,3-bisphospho-glycerate phosphatase reaction, quasi-steady states occur during the time-interval of about 0.5-2h incubation, which are defined by perturbed 2,3-bisphosphoglycerate concentrations. The theoretical predictions agree with experimental data. In the quasi-steady state the flux control is exerted almost entirely by the hexokinase-phosphofructokinase system. The model describes satisfactorily the time-dependent changes after addition of glucose to starved erythrocytes. The theoretical consequences are discussed of the conditions in vitro with lactate accumulation and the existence of a time-independent conservation quantity for the oxidized metabolites. Even in this closed system quasi-steady states occur which are characterized by approximately constant concentrations of all glycolytic metabolites except for the accumulation of lactate, fructose 1,6-bisphosphate and triose phosphate.
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PMID:The regulatory principles of glycolysis in erythrocytes in vivo and in vitro. A minimal comprehensive model describing steady states, quasi-steady states and time-dependent processes. 13 30


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