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)

An extension of a previous model [2] is proposed of the glycolysis of erythrocytes which includes realistic rat laws for the hexokinase-phosphofructokinase system and for the 2,3-P2G phosphatase. Whereas most conclusions previously drawn are reinforced, the mechanism of ATP regulation is different in the present model. The ATP concentration is mainly regulated by the inhibitory action of ATP and the activating effect of AMP on the phosphofructokinase. The role of the 2,3-P2G bypass as a buffer of changes in the ATP demand is of lesser significance than previously thought. Besides the feedback action of the adenine nucleotides on the hexokinase-phosphofructokinase system in the quasisteady state the role of 2,3-P2G as an energy source is important since it can yield ATP for a certain period of time. The present version of the model describes qualitatively the experimental data on the modulation of Na+-K+-ATPase.
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PMID:An extended model of the glycolysis in erythrocytes. 14 74

The possible presence of hexokinase in basal lateral membranes from rat kidney proximal tubules was investigated. Basal lateral membranes were obtained from homogenates of rat kidney cortex by differential centrifugation and free flow electrophoresis. They were further purified by density gradient centrifugation. Hexokinase activity was measured as the phosphorylation of D-[U14C]glucose. Throughout the purification of the membranes, the specific activity of hexokinase decreased while that of (Na+ + K+)-ATPase increased. Hexokinase activity in all fractions could be quantitatively accounted for in terms of cytosolic and mitochondrial enzyme contributions. It is concluded that there is no hexokinase activity in basal lateral membranes from rat kidney.
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PMID:Is hexokinase present in the basal lateral membranes of rat kidney proximal tubular epithelial cells? 14 9

Content of lactate, pyruvate as well as activity of hexokinase, phosphorylases, ATPase and transaminases were studied in dog and rat liver tissues under conditions of acute profuse hemorrhage and after its complete compensation by autogenic, isogenic blood and by sodium chloride 0.9% solution. Distinct inhibition of the hexokinase activity in the hemorrhage led to impairment of glucose utilization in liver tissue and to development of hyperglycemia. Alterations in arterial blood pressure correlated with the activity of tissue enzymes. Tissue metabolism was improved after compensation of blood losses by adequate amounts of blood at early period of hemorrhagic shock.
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PMID:[Liver metabolism during massive hemorrhage and subsequent blood transfusion]. 14 25

Carbamyl phosphate synthetase from Escherichia coli has been shown to use only the A isomer of adenosine-5'-[2-thiotriphosphate] in both the ATPase reaction (MgATP HCO3- leads to MgADP + Pi) and the carbamyl phosphate synthesis reaction (2MgATP + HCO3- + L-glutamine leads to 2MgADP + Pi + carbamyl-P + L-glutamate). The B isomer was less than 5% as reactive. In the reverse reaction, only the A isomer of adenosine-5'-[2-thiotriphosphate] is synthesized from adenosine-5'-[2-thiodiphosphate] and carbamyl-P as determined by 31P NMR and a coupled enzymatic assay with Cd2+- hexokinase. It is therefore proposed that carbamyl phosphate synthetase uses the same diastereomer of MgATP at both ATP sites.
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PMID:Carbamyl phosphate synthetase of Escherichia coli uses the same diastereomer of adenosine-5'-[2-thiotriphosphate] at both ATP sites. 21 Nov 24

Erythrocytes of patients with chronic kidney insufficiency exhibited high hexokinase activity as well as low activity of acetylcholinesterase and K+, Na+-dependent ATPase. The Km value of acetylcholinesterase for acetyl thiocholine was not altered in the reaction and the enzyme proved to be more resistant to heat denaturation. Therapy with permanent hemodialysis [8-10 hrs per day within some months] normalized K+, Na+-dependent ATPase activity and activated acetylcholinesterase. These effects may be considered as evidence for detoxication and normalization of metabolism. At the same time, high hexokinase activity and increased resistance of acetylcholinesterase to heat inactivation were maintained.
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PMID:[Effect of hemodialysis on erythrocyte acetylcholinesterase and adenosine triphosphatase activity in chronic renal insufficiency]. 22 70

1. Of the 15 tyrosyl residues/subunit of yeast hexokinase A (ATP:D-hexose 6-phosphotransferase) only one residue is specifically modified at pH 8.0 with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride. 2. The acylation of this single tyrosyl residue leads to the loss of the enzyme activities (hexokinase and ATPase) by a first-order process, which can be fully reversed by treatment with hydroxylamine. 3. ATP does not protect the enzyme against chemical modification and inactivation; however, glucose exerts a noticeable though indirect protection effect against chemical modification and inactivation. 4. The chemically modified enzyme, purified by column chromatography, has 14% of the activity of the native enzyme, but the Km for ATP-Mg or glucose remains unchanged as does the pH optimum of activity. Results of conformational studies (ultracentrifugation, fluorescence, thermostability and chemical reactivity of the sulfhydryl groups) indicate that the decrease of enzyme activity due to the modification of the tyrosyl residue is related to a localized perturbation of the enzyme active-center region.
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PMID:Chemical studies on yeast hexokinase. Specific modification of a single tyrosyl residue with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. 32 12

Keeping constant cellular magnesium an A 23 187 mediated moderate calcium loading of human red cells causes isoosmotic cell shrinkage, potassium efflux, slight decrease of cellular pH, ATP depletion connected with an increase of AMP, ADP and Pi and enhanced lactic acid formation. The calcium loading and accompanying effects can be abolished by EGTA or by extracellular magnesium, the latter kept more than two orders of magnitude above that of calcium which was 30 micrometer. Inhibition of the (Mg2+ + Ca2+)-dependent ATPase by ruthenium red or lanthanum decreases the calcium stimulated lactic acid formation after a lag phase. However, the ATP depletion proceeds faster and is much more pronounced under these conditions. (Mg+2 + Na+ +K+)-dependent ATPase, hexokinase, phosphofructokinase and cell shrinkage are ruled out, too, as mediators of the ATP depletion. This suggests that an unknown ATP consuming reaction, apparently not being related to the calcium pump, causes the calcium induced ATP depletion.
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PMID:Relations between ion shifting, ATP depletion and lactic acid formation in human red cells during moderate calcium loading using the ionophore A 23187. 33 40

1. We have developed a procedure for preparing resealed red cell ghosts that contain ADP but very little ATP. 2. The procedure involves (i) lysis of the cells in a very large volume of lysing solution, (ii) resuspension of the ghosts in a small volume, (iii) the incorporation into the ghosts, before they are resealed, of the adenylate kinase inhibitor P1,P5-di(adenosine-5'-)pentaphosphate (AP5A) and of hexokinase, and (iv) the removal of traces of ATP, formed by residual adenylate kinase activity, by the addition of glucose. 3. Measurements of sodium efflux from ghosts prepared in this way show that sodium-sodium exchange through the sodium pump does not occur in the absence of ATP even if ADP is present. 4. The beta:gamma imido analogue of ATP (AMP.PNP), which is incapable of phosphorylating sodium, potassium-ATPase, cannot replace ATP in supporting sodium-sodium exchange. 5. These findings support the hypothesis that the outward movement of sodium ions through the sodium pump is associated with the transfer of a phosphoryl group from ATP to the enzyme, and that the inward movement of sodium ions through the pump is associated with the return of a phosphoryl group from the phosphoenzyme to ADP.
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PMID:Sodium-sodium exchange through the sodium pump: the roles of ATP and ADP. 53 26

Several glycolytic enzymes were observed to have between 40-90% of their activities associated with the particulate fractions of lysed nerve endings. The enzymes showing high particulate activity in lysed nerve endings were hexokinase (EC 2.7.1.1), aldolase (EC 4.1.2.13), glucosephosphate isomerase (EC 5.3.1.9), phosphofructokinase (EC 2.7.1.11), glyceraldehyde-phosphate dehydrogenase (EC 1.2.1.12), pyruvate kinase (EC 2.7.1.40) and lactate dehydrogenase (EC 1.1.27). With the exception of phosphofructokinase, 80% or more of the particle associated activity of each enzyme was solubilized by salt treatment indicating the association with particles was ionic. Sub-fractionation of lysed nerve endings showed hexokinase and fumarase (EC 4.2.1.2) had the highest specific activity in the same fractions which is consistent with observations indicating that hexokinase is associated with mitochondria. The other glycolytic zymes having high particulate activity, aldolase, glucosephosphate isomerase, phosphofructokinase, glyceraldehyde-phosphate dehydrogenase, pyruvate kinase and lactate dehydrogenase, showed enrichment in fractions containing synaptosomal membranes, i.e. the fractions having highest specific activity of acetylcholinesterase (EC 3.1.1.7) and (Na+ + K+)-ATPase (EC 3.6.1.3).
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PMID:Association of glycolytic enzymes with particulate fractions from nerve endings. 62 35

1. The preparation of rat heart mitochondria with Potter-Elvehjem homogenizer results in mitochondria showing stimualtion of respiration induced by Mg2+. This stimualtion is neither caused by adherent hexokinase nor by energy-dependent magnesium accumulation (Mg2+ content in the presence of 10 mM glutamate: 22 nmoles/mg protein; in the presence of glutamate plus antimycin A 21 nmoles/mg protein). 2. The effect of added magnesium is excluded by addition of carboxyatractyloside. This demonstrates the activity of an ATPase outside of the mitochondrial inner membrane. 3. A simple and rapid method for the preparation of Mg2+-insensitive rat heart mitochondria is presented. The minced heart is pressed through a normal syringe and then treated with trypsin. 4. A comparison of mitochondria of both preparations shows that there is no difference in magnesium content and no energy-dependent magnesium influx.
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PMID:Influence of Mg2+-ions on the properties of rat heart mitochondria in dependence on the preparation. 70 27


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