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)

Erythrocyte glycolysis has been studied in the anaemia associated with protein-energy malnutrition (PEM) in Kivu. Several results were compatible with a lowering of the mean age of the erythrocyte population, notably raised levels of glucose-6-phosphate, hexokinase, Na+-K+- adenosinetriphosphatases and potassium, and low sodium concentration. Non-significant differences were observed for glucose utilization, lactate formation, and for concentrations of fructose-6-phosphate, fructose-1,6-diphosphate, adenosine diphosphate and pyruvate kinase; there was no gross disturbance of cation transport. The level of adenosine triphosphate was slightly decreased and that of 2,3-bisphosphoglycerate was not elevated, in spite of anaemia. The latter could not be explained by an instability of this metabolite. It is concluded that slight erythrocyte glycolytic abnormalities may occur in the anaemia of Kivu PEM, but that they are not the main cause of the haemolysis observed in this syndrome.
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PMID:Erythrocyte glycolysis in protein-energy malnutrition. 629 Jan 7

Repeated washing of a brain mitochondrial fraction results in a progressive decrease in the proportion of mitochondrially bound hexokinase that can be solubilized during a subsequent incubation with glucose-6-phosphate (glucose-6-P). Phospholipids removed during the washing procedure can be added back to washed mitochondria, resulting in enhancement of the solubilization by glucose-6-P. Column and thin-layer chromatographic methods have been used to isolate and identify active phospholipids. Additional studies were performed with purified lipids obtained commercially. Both lysophospholipids and acidic phospholipids were active in enhancing solubilization of hexokinase by glucose-6-P. Phospho-inositides, particularly diphosphoinositide, were quite effective, raising the possibility that the actively metabolized phosphoinositides may be involved in regulation of hexokinase binding in vivo.
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PMID:The influence of specific phospholipids on the interaction of hexokinase with the outer mitochondrial membrane. 631 76

Addition of glucose-6-phosphate (0.03-0.06 mM) to a suspension of rat lung mitochondria promotes solubilization of 30 to 85% of the bound form of hexokinase. This effect is significantly enhanced by the simultaneous addition of glucose (10 mM), fructose (10 mM) or mannose (10 mM). Conversely addition of N-acetylglucosamine (10 mM), mannose-6-phosphate (10 mM) or inorganic phosphate (1 mM) reduces hexokinase solubilization. Insulin is involved in the regulation of the interaction between mitochondrial membrane and hexokinase. Treatment with alloxan causes an increase of the free form of the enzyme in the lung and a correspondent reduction of the bound form. Insulin administration restores the normal intracellular distribution of the enzyme.
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PMID:Rat lung hexokinase: some aspects of the metabolic and hormonal regulation of its subcellular distribution. 635 4

Previous studies with lens dispersions indicated that the rate-limiting step in glycolysis shifts from hexokinase (HK) in the young lens to phosphofructokinase (PFK) in older lenses. Because the concentrations of the complex controlling factor for these enzymes could not be reproduced reliably in homogenates, the question of age-related control of glycolysis was re-examined in intact lenses. Toward this end, the levels of several metabolites of glucose were measured in fresh and incubated clear lenses. Of the substrates measured per fresh lens, only one changed significantly with age; fructose diphosphate was increased. When lenses were incubated in 2 to 12 mM glucose, the lactate production per lens was not significantly different with age. Together these results suggested that the glycolytic mass of the lens was constant with age. In both young and older lenses, increases in glucose in the medium led to increases in both glucose and glucose-6-phosphate in the lens. The lack of corresponding increase in lactate production suggested that the regulatory step lay downstream from HK, probably at PFK. This finding was corroborated by evidence that the initial acceleration of lactate production by the addition of cyanide (the Pasteur effect) was accompanied by decreases in the substrates of PFK, glucose-6-phosphate and fructose-6-phosphate. A secondary disinhibition of HK, as indicated by decreased lens glucose, became apparent after longer incubation with cyanide. This suggested that after disinhibition of PFK, HK became rate-limiting until the level of glucose-6-phosphate fell enough to allow the disinhibition of the latter enzyme as well. Thus PFK seemed to be the primary regulatory step in aerobic glycolysis in lenses of rats from 1 to 12 months of age.
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PMID:Age and the control of glycolysis in the rat lens. 645 26

Assay of the activities of hexokinase, phosphofructokinase, and pyruvate kinase showed that the first two declined in aging human lens cortex and all three enzymes retained constant activities in the epithelium throughout life. Moreover, both clear and cataractous aging lenses contained the same enzyme activities. ATP contents in cataracts, however, were lower than in clear lenses; in fact, after incubation at 37.5 degrees C in isotonic (290 to 300 mOsm), glucose-containing media, ATP was rapidly lost from cataracts (but not from clear lenses), suggesting excessive ATP expenditure in cataracts for osmotic balance. Cataracts incubated in media containing either glucose-6-phosphate or fructose-1, 6-diphosphate produced significantly higher ATP than with glucose in the media, indicating that glucose metabolism in human senile cataracts could be supplemented with hexose phosphates. Fructose-1, 6-diphosphate appeared to be more efficient than glucose-6-phosphate in preventing lens swelling during incubation.
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PMID:Supplementing glucose metabolism in human senile cataracts. 645 78

The purpose of the present investigation was to compare the solubilizing effect of methohexital on the mitochondrially bound hexokinase activity in brain and heart tissue of the rat. Experiments were performed using intact rats, the isolated perfused rat brain and heart as well as mitochondrial fractions from rat brain and heart tissue. It was shown that bound hexokinase activity was significantly solubilized by methohexital in brain tissue in vivo and in the isolated perfused rat brain but no effect was demonstrable in heart tissue. When mitochondrial fractions were incubated with methohexital in vitro, hexokinase activity was significantly solubilized from brain mitochondria but only slightly from heart mitochondria although glucose-6-phosphate was able to displace hexokinase also from heart mitochondria. The results suggest that mitochondrially bound hexokinase activity in brain tissue is particularly sensitive against the solubilizing effect of anesthetics. This effect could contribute to the sensitivity of brain function and metabolism against anesthetic drugs.
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PMID:Comparison of rat brain and heart mitochondrial hexokinase solubilized by methohexital. 647 87

Erythrocytes of individuals with increased (+ 50%) or reduced (-35%) hexokinase activity contain respectively 70 and 17 nmole/ml RBC of glucose-6-phosphate (normal concentration 30 +/- 5nmole/ml RBC) and show comparable rates of the HMP (60 +/- 5nmole/hr/ml RBC). Similarly, in RBC of different ages, obtained by density gradient ultracentrifugation, the glucose-6-phosphate concentration range from 57 (young cells) to 18 (old cells) nmole/ml RBC but the rate at which glucose is utilized in the HMP is unchanged. These data exclude a regulatory role of glucose 6-phosphate in the HMP even if its concentration is under that required for maximal G6PD activity.
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PMID:Relationship between the rate of erythrocyte hexose monophosphate pathway and the glucose 6-phosphate concentration. 650 92

Biopsies from 15 human gliomas, five meningiomas, four Schwannomas, one medulloblastoma, and four normal brain areas were analyzed for 12 enzymes of energy metabolism and 12 related metabolites and cofactors. Samples, 0.01-0.25 microgram dry weight, were dissected from freeze-dried microtome sections to permit all the assays on a given specimen to be made, as far as possible, on nonnecrotic pure tumor tissue from the same region. Great diversity was found with regard to both enzyme activities and metabolite levels among individual tumors, but the following generalities can be made. Activities of hexokinase, phosphorylase, phosphofructokinase, glycerophosphate dehydrogenase, citrate synthase, and malate dehydrogenase levels were usually lower than in brain; glycogen synthase and glucose-6-phosphate dehydrogenase were usually higher; and the averages for pyruvate kinase, lactate dehydrogenase, 6-phosphogluconate dehydrogenase, and beta-hydroxyacyl coenzyme A dehydrogenase were not greatly different from brain. Levels of eight of the 12 enzymes were distinctly lower among the Schwannomas than in the other two groups. Average levels of glucose-6-phosphate, lactate, pyruvate, and uridine diphosphoglucose were more than twice those of brain; 6-phosphogluconate and citrate were about 70% higher than in brain; glucose, glycogen, glycerol-1-phosphate, and malate averages ranged from 104% to 127% of brain; and fructose-1,6-bisphosphate and glucose-1,6-bisphosphate levels were on the average 50% and 70% those of brain, respectively.
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PMID:Diversity of metabolic patterns in human brain tumors: enzymes of energy metabolism and related metabolites and cofactors. 661 61

Red blood cell glucose metabolism was investigated in a male patient with de novo trisomy 10p. According to previous evidence, when assigning hexokinase gene locus in the 10p11 leads to pter region, a triplex dosage effect of hexokinase activity (HK) was found, while all the other erythrocyte glycolytic enzymes were in the normal values range. Red blood cell glucose utilization was 2.87 mumole/hr/ml RBC as compared to 1.43 in normal controls; the rate of glucose metabolized through the hexose monophosphate shunt (HMPS) was unchanged. Glucose-6-phosphate, fructose-6-phosphate, fructose-1,6-diphosphate, and dihydroxyacetone phosphate increased with respect to normal controls, while normal levels of 3-phosphoglycerate, 2-phosphoglycerate, phosphoenolpyruvate, and ATP were found. The HK activity increased in all the red blood cell fractions obtained by density gradient ultracentrifugation. However, a small difference in the distribution of cells through the gradient was evident. The experiments reported in this article show that in the red blood cells of patients with trisomy 10p, an increased level of HK leads to higher concentrations of glucose-6-phosphate and to a faster glucose utilization in the Embden-Meyerhof pathway, while the HMPS rate is unchanged.
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PMID:Red blood cell glucose metabolism in trisomy 10p: possible role of hexokinase in the erythrocyte. 683 Oct 53

1. In rat submandibular gland, hexokinase was distributed not only in cytosol fraction but also in mitochondrial fraction. 2. Glucose-6-phosphate and ATP were most effective substances on releasing hexokinase from mitochondria. However, all the hexokinase in mitochondria could not be extracted with these substances. 3. Concentrations of glucose-6-phosphate and ATP were decreased with the administration of epinephrine in vivo. 4. Increase of the amount of mitochondria-bound hexokinase was observed for 5 min with epinephrine administration, and it returned to the control level after 10 min. 5. In rat submandibular gland, mitochondrial hexokinase may reversibly bind to and release from mitochondria as observed in brain.
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PMID:Distribution and regulation of mitochondrial hexokinase in rat submandibular gland. 683 61


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