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)

Yeast hexokinase A(ATP:D-hexose 6-phosphotransferase) is inactivated when incubated in the presence of xylose and ATPMg, or in the presence of D-lyxose in a reaction medium in which ATPMg is being continuously regenerated (phosphoenolpyruvate and pyruvate kinase). The inactivation is due to the phorphorylation of the protein. A linear relationship was observed between the inactivation and the incorporation of 32P from [gamma-32P] ATP. All hexokinase and ATPase activity of the enzyme is lost when one phosphoryl group is incorporated per enzyme subunit (molecular weight 51,000). The phosphoryl group is covalently bound by a ester linkage with a serine residue of the protein.
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PMID:Studies on the active site of yeast hexokinase. Specific phosphorylation of a serine residue induced by D-xylose and ATPMg. 0 82

(1) The mitochondrial ATPase (EC 3.6.1.3) Ehrlich ascites cell mitochondria, was inhibited by D-glucose under physiological concentrations of ATP. The generation of ADP by the mitochondrial bound hexokinase, seems to be the reason for the D-glucose inhibitory effect. Reversal of the inhibitory effect of ADP on Ehrlich ascites cell mitochondria ATPase by an ATP-regenerating system was achieved. (2) Dissociation of mitochondrial bound hexokinase from the mitochondria eliminated the inhibitory effect of D-glucose. Rebinding of the hexokinase to the mitochondria regenerated the D-glucose inhibitory effect on Ehrlich ascites cell mitochondria ATPase. (3) Bioflavonoids such as quercetin inhibit the mitochondrial hexokinase activity, but do not change the mitochondrial ATPase activity of isolated Ehrlich ascites tumor cell mitochondria. (4) The inhibitory effect of bioflavonoids on mitochondrial bound hexokinase activity is shown to be dissociable from the ascites tumor cell mitochondria and seems to be associated with regulatory rather than catalitic sites of the enzyme.
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PMID:Bioflavonoid regulation of ATPase and hexokinase activity in Ehrlich ascites cell mitochondria. 1 95

Vesicles were reconstituted from a purified dicyclohexyl-carbodiimide-sensitive ATPase complex (TF0-F1) and phospholipids of a thermophilic bacterium PS3. These vesicles synthesized ATP from ADP and Pi with energy from an electrochemical proton gradient (delta-micronH+) formed by a pH gradient and an electrical potential across their membranes. Maximal ATP synthesis was achieved by incubating the vesicles in malonate at pH 5.5 with valinomycin, and then rapidly transferring them to a solution of pH 8.4 and 150 mM K+. Under these conditons ATP synthesis continued at a decreasing rate for 30 s at 40 degrees. Appreciable formation of ATP (40 to 150 nmol/mg of TF0-F1) occurred at an initial delta-micronH+ above 205 mV and moderate formation at an initial value above 180 mV. ATP hydrolysis by the vesicles produced a delta-micronH+, and the additions of 32Pi and hexokinase to them resulted in 32Pi esterification. Analysis of the time courses of 32Pi esterification and decays of the pH difference and membrane potential, followed using 9-aminoacridine and 8-anilinonaphthalene-1-sulfonate, respectively, as probes, showed a relationship between delta-micronH+ and the rate of ATP synthesis. These results demonstrate that purified TF0-F1 is itself a reversible H+-translocating ATPase of oxidative phosphorylation.
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PMID:Adenosine triphosphate synthesis by electrochemical proton gradient in vesicles reconstituted from purified adenosine triphosphatase and phospholipids of thermophilic bacterium. 1 11

We have previously shown that acute coronary occlusion in the dog is often accompanied by increased adrenaline release into the blood. In the present study the consequences of this humoral reaction were studied in anaesthetised healthy mongrel dogs subjected to adrenaline infusion administered at a rate relevant to spontaneous release of this amine in coronary occlusion. Adrenaline was infused in a dose of 1.2 microgram.kg-1.min-1 for 4 h. Dogs receiving saline served as the control. Adrenaline administration led to the decrease in insulin/glucose ratio, to a significant fall in serum triiodothyronine and in blood pH. Free fatty acid levels doubled. Histochemically, a diminution in succinic dehydrogenase and ATPase activity in adrenaline-treated hearts was found. A significant fall in the activity of mitochondrial hexokinase in these hearts was detected spectrophotometrically. Electron microscopic study revealed alterations in the mitochondrial structure. These findings indicate that an excess of adrenaline in ammounts similar to that seen in experimental infarction leads to profound metabolic and hormonal disturbances and exerts a detrimental effect upon myocardium.
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PMID:Evidence for the detrimental effect of adrenaline infused to healthy dogs in doses imitating spontaneous secretion after coronary occlusion. 2 14

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

Two reaction intermediates of H-meromyosin (HMM) ATPase [EC 3.6.1.3], E2AT32P, and (see article), were formed by mixing excess HMM with AT32P. Then a large excess of unlabelled ATP was added, and the amount of AT32P liberated from E2AT32P was measured as the difference between the total amount of AT32P in the reaction mixture and the amount of AT32P bound to HMM, obtained by filtering the mixture after adding charcoal to adsorb nucleotides (charcoal-filtration method). The amount of free AT32P was also measured as the amount of glucose-6-32P formed within 15 sec after adding large excesses of hexokinase [EC 2.7.1.1] and glucose to the reaction mixture. The rate constant, k-2, for the step E2ATP yields E plus ATP was calculated at various KCl concentrations from the time-course of liberation of AT32P. The intermediate, (see article), was formed by mixing HMM with AT32P in a molar ratio of 1:2, and the rate constant, k-6, for the step (see article) was also determined by the same procedures used for k-2. In 0.5 M KCl and 2 mM MgCl2 at pH 7.8 and 0 degrees, k-2 and k-6 were 0.002 sec-1 and 0.1 sec-1 or more, respectively. From the rate constants determined in this work and the rate and equilibrium constants which we reported previously, the standard free energy changes (kcal/mole) for formation of various reaction intermediates in the reaction of HMM ATPase in 0.5 M KCl and 2 mM MgCl2 at pH 7.8 and 0 degrees were calculated to be as follows: (see article).
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PMID:Standard free energy changes for formation of various intermediates in the reaction of H-meromyosin ATPase. 12 76

The control theory of steady states, previously presented for linear enzymatic systems (Heinrich and Rapoport, 1974) is extended to nonlinear systems. On the basis of three theorems a new procedure for the calculation of the control strength and of the control matrix is developed. The theory is applied to the extended model of glycolysis of erythrocytes, which includes also ATP-consuming processes. Also in this model the glycolytic flux is mainly controlled by the hexokinase-phosphofructokinase-system. The control strengths of the pyruvate kinase and of the enzymes of the 2.3 P2G-bypass are negligibly small. The control strength of the ATPase is negative, i.e. an activation of this enzyme leads to a decrease of the flux. For transition states of multienzyme systems definitions are given for the mean time required for the transition of the metabolites and for the "transient control" of enzymes. Enzymes with a pronounced influence on the transition time are called time-limiting enzymes. Enzymes which excert strong control on the time-dependent processes may have little influence under steady state conditions and vice versa. The transition times of ATP have been calculated for transient states of glycolysis.
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PMID:Mathematical analysis of multienzyme systems. II. Steady state and transient control. 12 16

Spinach chloroplasts were able to photophosphorylate the ADP analog alpha,beta-methylene adenosine 5'-diphosphate (AOPCP). Phosphorylation of AOPCP was catalyzed by chloroplasts that were washed or dialyzed to remove free endogenous nucleotides. In the presence of glucose, hexokinase, AOPCP and 32Pi, the 32P label was incorporated into alpha,beta-methylene adenosine 5'-triphosphate (AOPCPOP). In contrast to photophosphorylation of AOPCP, the ATP analog AOPCPOP was a poor substrate for the ATP-Pi exchange reaction and its hydrolysis was neither stimulated by light and dithiothreitol nor inhibited by Dio-9. Photophosphorylation of AOPCP was inhibited by the alpha,beta- and beta,gamma-substituted methylene analogs of ATP, while phosphorylation of ADP was unaffected by them. The ATP-Pi exchange was also unaffected by both ATP analogs, while the weak AOPCPOP-Pi exchange was inhibited by the beta,gamma-methylene analog of ATP. Direct interaction of methylene analogs with the chloroplast coupling factor ATPase was indicated by the enzymatic hydrolysis of AOPCPOP on polyacrylamide gels.
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PMID:Studies on photophosphorylation utilizing methylene diphosphonate analogs of ADP and ATP. 13 Sep 36

The activities of several glycolytic enzymes (hexokinase, phosphofructokinase, pyruvate kinase, lactate dehydrogenase) as well as glycerol-1-phosphate dehydrogenase and (Mg2+)ATPase in normal cerebrospinal fluid (CSF) and blood plasma samples, from 12 healthy infants, aged 2-18 months, and in supernatants from brain tissue slices, taken during neurosurgical operations from infants of the same range of age were estimated. The values obtained confirm the high activity of the above enzymes found in animal brains, and indicate an independence of these activities in blood plasma and CSF. The origin of the activities of the investigated enzymes in CSF seems to be mainly, if not, exclusively, from brain tissue. This might be useful for detection of brain tissue damage as was earlier proven with LDH activity in CSF.
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PMID:Some glycolytic enzymes in normal cerebrospinal fluid, brain tissue and blood plasma of infants. 13 54

Administration of 60,000 i.e. of vitamin A into rats within three weeks caused an increase in amount of reticulocytes, in the rate of glucose utilization and in formation of lactic acid by erythrocytes. The activity of glycolytic enzymes was intensified. The activity of hexokinase was increased by 84.6%, activities of aldolase and phosphohexoisomerase were increased by 34%. But in the erythrocytes content of AMP, ADP and ATP was unaltered, probably due to activation of total and Na+, K+-dependent ATPase. The harmful effect of an excess of the vitamin A was manifested in an increased content of Na+ in erythrocytes and also in decreased stability of the cells to acid hemolytics.
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PMID:[Intensity of glycolysis and energy metabolism in erythrocytes in experimental hypervitaminosis A]. 13 57


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