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)

Human platelets were separated by desity-centrifugation into heavy and light populations. Heavy platelets have an average volume approximately twofold greater than light platelets, and have previously been shown to be young platelets. All 11 enzymes of the Embden-Meyerhof pathway plus the five related enzymes: phosphoglucomutase, glucose-6-P dehydrogenase, 6-P-gluconic dehydrogenase, alpha-glycerol-P dehydrogenase, and glutathione reductase (TPNH) were examined in cell lysates from total, heavy, and light platelet populations. Apparent Km for individual enzymes were measured in a total platelet population. Empirical V(max) of the individual enzymes were measured in total, heavy, and light platelet populations. The three apparent rate-limiting enzymes for glycolysis were hexokinase, phosphofructokinase, and glyceraldehyde-3-P dehydrogenase. Heavy platelets contained approximately twofold greater enzyme activity (per gram wet weight) than light platelets for 7 of the 16 enzymes measured: hexokinase, phosphohexoisomerase, phosphofructokinase, glyceraldehyde-3-P dehydrogenase, phosphoglycerokinase, lactic dehydrogenase, and phosphoglucomutase. Heavy platelets also contained 1.9-fold greater reduced glutathione (GSH), 1.7-fold greater DPNH, and 1.2-fold greater TPNH than light platelets. Heavy platelets contained 1.8-fold less lipid peroxidation products (malonyl aldehyde equivalents) than light platelets and were 2.4-fold more resistant to lipid peroxidation catalyzed by 0.1 mM FeCl(3). Sterile incubation of heavy platelets, in vitro for 17 hr, resulted in a significant loss of enzyme activity for the "elevated" seven enzymes when compared with the remainder. Reducing agents such as GSH (0.1 mM), ascorbic acid (0.1 mM), and dithiothreitol (0.01 mM), when added to the incubation mixture, significantly reduced the in vitro loss of activity. In vitro incubation was also associated with a significant loss of GSH and DPNH and a 1.8-fold increase in lipid peroxidation products.
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PMID:Heterogeneity of human platelets. V. Differences in glycolytic and related enzymes with possible relation to platelet age. 426 50

1. The deoxyfluoro-d-glucopyranose 6-phosphates were prepared from the corresponding deoxyfluoro-d-glucoses and ATP by using hexokinase. 2. 3-Deoxy-3-fluoro- and 4-deoxy-4-fluoro-d-glucose 6-phosphate were substrates for glucose phosphate isomerase, and in addition the products of this reaction, 3-deoxy-3-fluoro- and 4-deoxy-4-fluoro-d-fructose 6-phosphate respectively, were good substrates for phosphofructokinase. 3. Some C-2-substituted derivatives of d-glucose 6-phosphate were found to be competitive inhibitors of glucose phosphate isomerase. 4. The possible role of the hydroxyl groups in the binding of d-glucose 6-phopshate to glucose phosphate isomerase is discussed.
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PMID:The deoxyfluoro-D-glucopyranose 6-phosphates and their effect on yeast glucose phosphate isomerase. 426 21

Increasing concentrations of sodium octanoate were progressively inhibitory to the activities of glucokinase, hexokinase, phosphofructokinase, and pyruvate kinase. Glucose-6-phosphate and 6-phosphogluconate dehydrogenases were also markedly inhibited. Other enzymes of carbohydrate metabolism such as lactate dehydrogenase, phosphohexose isomerase, and fructose-1,6-diphosphatase were not decreased. Among the key glycolytic enzymes, the inhibition of pyruvate kinase by the fatty acid was most marked. The biological significance of the inhibition of the key glycolytic enzymes is interpreted as a feedback inhibitory mechanism in regulation of fatty acid biosynthesis. The mechanism may function for rapid adaptation by which the organism can use the fatty acid level as a metabolic directional switch in decreasing glycolysis and turning on gluconeogenesis.
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PMID:Feedback inhibition of key glycolytic enzymes in liver: action of free fatty acids. 428 79

1. The activities of six enzymes (hexokinase, phosphoglucose isomerase, phosphofructokinase, aldolase, glucose 6-phosphate dehydrogenase and amylase) in extracts of pea cotyledons were determined. The activities during the first 10 days after germination showed individual and characteristic changes that indicate a specific control of both synthesis and destruction of enzymes. 2. Tissue contents of glucose, inorganic phosphate, glucose 6-phosphate, fructose 6-phosphate, ATP, ADP, AMP, NAD and NADP were also determined, and a correlation is reported between the substrate concentrations at day 1 and the subsequent enzymic activity. 3. The initial NAD(+)/NADH ratio value of 1 changed to about 3 by day 4; the NADP content was lower and changes in the oxidation state were less striking. The ratio of ATP to ADP and AMP remained virtually constant.
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PMID:Correlated changes of some enzyme activities and cofactor and substrate contents of pea cotyledon tissue during germination. 438 39

1. Adipose tissues from rats fed a balanced diet were incubated in the presence of glucose (20mm) with the following additions: insulin, anti-insulin serum, insulin+acetate, insulin+pyruvate, insulin+lactate, insulin+phenazine methosulphate, insulin+oleate+albumin, insulin+adrenaline+albumin, insulin+6-N-2'-O-dibutyryl 3':5'-cyclic AMP+albumin. 2. Measurements were made of the whole tissue concentrations of adenine nucleotides, hexose phosphates, triose phosphates, glycerol 1-phosphate, 3 phosphoglycerate, 6-phosphogluconate, long-chain fatty acyl-CoA, acid-soluble CoA, citrate, isocitrate, malate and 2-oxoglutarate, and of the release into the incubation medium of lactate, pyruvate and glycerol after 1h of incubation. 3. Fluxes of [(14)C]glucose carbon through the major pathways of glucose metabolism were calculated from the yields of (14)C in various products after 2h of incubation. Fluxes of [(14)C]acetate, [(14)C]pyruvate or [(14)C]lactate carbon in the presence of glucose were also determined. 4. Measurements were also made of the whole-tissue concentrations of metabolites in tissues taken directly from Nembutal-anaesthetized rats. 5. Whole tissue mass-action ratios for phosphofructokinase, phosphoglucose isomerase and the combined (aldolasextriose phosphate isomerase) reaction were similar in vivo and in vitro. The reactants of phosphofructokinase appeared to be far from mass-action equilibrium. In vitro, the reactants of hexokinase also appeared to be far from mass-action equilibrium. 6. Correlation of observed changes in glycolytic flux with changes in fructose 6-phosphate concentration suggested that phosphofructokinase may show regulatory behaviour. The enzyme appeared to be activated in the presence of oleate or adrenaline and to be inhibited in the presence of lactate or pyruvate. 7. Evidence is presented that the reactants of lactate dehydrogenase and glycerol 1-phosphate dehydrogenase may be near to mass-action equilibrium in the cytoplasm. 8. No satisfactory correlations could be drawn between the whole-tissue concentrations of long-chain fatty acyl-CoA, citrate and glycerol 1-phosphate and the observed rates of triglyceride and fatty acid synthesis. Under the conditions employed, the concentration of glycerol 1-phosphate appeared to depend mainly on the cytoplasmic [NAD(+)]/[NADH] ratios. 9. Calculated hexose monophosphate pathway flux rates roughly correlated with fatty acid synthesis rates and with whole tissue [6-phosphogluconate]/[glucose 6-phosphate] ratios. The relative rates of production of NADPH for fatty acid synthesis by the hexose monophosphate pathway and by the ;malic enzyme' are discussed. It is suggested that all NADH produced in the cytoplasm may be used in that compartment for reductive synthesis of fatty acids, lactate or glycerol 1-phosphate.
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PMID:The regulation of triglyceride synthesis and fatty acid synthesis in rat epididymal adipose tissue. 439 81

1. The intracellular distribution of hexokinase activity was studied in the mucosa of rat and guinea-pig small intestine. In the rat 60% and in the guinea pig 45% of the hexokinase activity of homogenates were recovered in a total particulate fraction that contained only 5-17% of the homogenate activity of hexose phosphate isomerase, pyruvate kinase, lactate dehydrogenase and overall glycolysis (formation of lactate from glucose). 2. Fractionation of homogenates from guineapig small intestine showed that the particulate hexokinase activity was chiefly in the mitochondrial fraction with a small proportion in the nuclei plus brush-border fraction. 3. After chromatography of the particle-free supernatants on DEAE-cellulose, hexokinase types I and II were determined quantitatively. No evidence was obtained for the presence of hexokinase type III or glucokinase. In the preparations from guinea pigs, hexokinase types I and II amounted to 69% and 31% respectively of the eluted activity; the corresponding values for preparations from rats were 5.8% and 94.2%. 4. Total and specific hexokinase activities decreased significantly in homogenates and particle-free supernatants prepared from the intestinal mucosa of rats starved for 36hr. and increased again after re-feeding. The decrease in hexokinase activity in the particle-free supernatant from starved rats was chiefly due to a decrease in the type II enzyme.
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PMID:Glucose metabolism in the mucosa of the small intestine. A study of hexokinase activity. 566 46

1. Measurements were made of the non-oxidative reactions of the pentose phosphate cycle in liver (transketolase, transaldolase, ribulose 5-phosphate epimerase and ribose 5-phosphate isomerase activities) in a variety of hormonal and nutritional conditions. In addition, glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase activities were measured for comparison with the oxidative reactions of the cycle; hexokinase, glucokinase and phosphoglucose isomerase activities were also included. Starvation for 2 days caused significant lowering of activity of all the enzymes of the pentose phosphate cycle based on activity in the whole liver. Re-feeding with a high-carbohydrate diet restored all the enzyme activities to the range of the control values with the exception of that of glucose 6-phosphate dehydrogenase, which showed the well-known ;overshoot' effect. Re-feeding with a high-fat diet also restored the activities of all the enzymes of the pentose phosphate cycle and of hexokinase; glucokinase activity alone remained unchanged. Expressed as units/g. of liver or units/mg. of protein hexokinase, glucose 6-phosphate dehydrogenase, transketolase and pentose phosphate isomerase activities were unchanged by starvation; both 6-phosphogluconate dehydrogenase and ribulose 5-phosphate epimerase activities decreased faster than the liver weight or protein content. 2. Alloxan-diabetes resulted in a decrease of approx. 30-40% in the activities of 6-phosphogluconate dehydrogenase, ribose 5-phosphate isomerase, ribulose 5-phosphate epimerase and transketolase; in contrast with this glucose 6-phosphate dehydrogenase, transaldolase and phosphoglucose isomerase activities were unchanged. Treatment of alloxan-diabetic rats with protamine-zinc-insulin for 3 days caused a very marked increase to above normal levels of activity in all the enzymes of the pentose phosphate pathway except ribulose 5-phosphate epimerase, which was restored to the control value. Hexokinase activity was also raised by this treatment. After 7 days treatment of alloxan-diabetic rats with protamine-zinc-insulin the enzyme activities returned towards the control values. 3. In adrenalectomized rats the two most important changes were the rise in hexokinase activity and the fall in transketolase activity; in addition, ribulose 5-phosphate epimerase activity was also decreased. These effects were reversed by cortisone treatment. In addition, in cortisone-treated adrenalectomized rats glucokinase activity was significantly lower than the control value. 4. In thyroidectomized rats both ribose 5-phosphate isomerase and transketolase activities were decreased; in contrast with this transaldolase activity did not change significantly. Hypophysectomy caused a 50% fall in transketolase activity that was partially reversed by treatment with thyroxine and almost fully reversed by treatment with growth hormone for 8 days. 5. The results are discussed in relation to the hormonal control of the non-oxidative reactions of the pentose phosphate cycle, the marked changes in transketolase activity being particularly outstanding.
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PMID:The pentose phosphate pathway of glucose metabolism. Hormonal and dietary control of the oxidative and non-oxidative reactions of the cycle in liver. 579 34

1. Measurements were made of the activities of enzymes of the pentose phosphate cycle, glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, ribose 5-phosphate isomerase, ribulose 5-phosphate epimerase, transketolase and transaldolase, as well as of the related or competing enzymes glucokinase, hexokinase, phosphoglucose isomerase and phosphoglucomutase, in control rats and in rats bearing the growth-hormone- and prolactin-secreting pituitary tumour MtTW5, to study the effect of high endogenous concentrations of growth hormone on this pathway in liver. 2. There was a twofold increase in liver weight. Glucokinase activity/g. of liver decreased to half the control value in the experimental group, although on a total liver basis it remained unchanged. Hexokinase activity increased in parallel with the liver weight, so that the total activity was doubled in rats with a high endogenous concentration of growth hormone. No differences in response were found between heat-stable and heat-labile forms of hexokinase. 3. The activity/g. of liver of the two oxidative enzymes of the pathway decreased slightly in the experimental group, but this was offset by the increase in liver weight, and the resultant effect was a 50% increase in the total activity. 4. Of the non-oxidative enzymes of the cycle the most marked increase on a total liver basis was in ribose 5-phosphate isomerase activity, to 2.5 times the control value. Ribulose 5-phosphate epimerase activity showed the smallest increase. Transketolase and transaldolase activities were also increased. The latter is the rate-limiting enzyme of the non-oxidative reactions of the cycle in these animals. 5. The results are discussed in relation to the glycolytic pathway and synthesis of glycogen, and more particularly to the increased requirement for ribose 5-phosphate for RNA synthesis.
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PMID:The pentose phosphate pathway of glucose metabolism. Influence of a growth-hormone-secreting pituitary tumour on the oxidative and non-oxidative reactions of the cycle in liver. 580 93

1. Measurements were made of the activities of the enzymes of the pentose phosphate pathway concerned in both the oxidative (glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase) and the non-oxidative (ribose 5-phosphate isomerase, ribulose 5-phosphate epimerase, transketolase and transaldolase) reactions of this pathway, together with hexokinase and phosphoglucose isomerase, in adipose tissue in a variety of nutritional and hormonal conditions. 2. Starvation for 2 days caused a significant decrease in the activities of all the enzymes of the pentose phosphate pathway, with the exception of glucose 6-phosphate dehydrogenase, when expressed as activity/2 fat-pads; only the activities of ribose 5-phosphate isomerase and ribulose 5-phosphate epimerase were significantly decreased on the basis of activity/mg. of protein. Re-feeding with a high-carbohydrate or high-fat diet for 3 days restored the activity of all the enzymes of the pentose phosphate pathway to the range of the control values, with the exception of transketolase, which showed a marked ;overshoot' in rats re-fed with carbohydrate. Starvation for 3 days caused a marked decrease in the activities of glucose 6-phosphate dehydrogenase and transketolase. 3. On the basis of activity/two fat-pads, alloxan-diabetes caused a marked decrease, to about half the control value, in the activities of all the enzymes concerned in the pentose phosphate pathway, transketolase showing the smallest decrease; hexokinase and phosphoglucose isomerase activities were also decreased. Treatment with insulin for 3 and 7 days raised the activities to normal or supranormal values, transketolase showing the most marked ;overshoot' effect. On the basis of activity/mg. of protein the activity of none of the enzymes was significantly decreased in alloxan-diabetes; transketolase and transaldolase activities were raised above the control values. With insulin treatment for 3 or 7 days the activities of all the enzymes were significantly increased, except that of ribulose 5-phosphate epimerase at the shorter time-interval. Glucagon treatment did not alter any of the enzyme activities expressed on either basis. 4. Thyroidectomy caused a decrease of 30-40% in the activities of enzymes of the pentose phosphate pathway, except for transketolase activity, which fell to 50% of the control value. Little change occurred in adipose-tissue weight or protein content. 5. Adrenalectomy caused a decrease of 40% in the activity of glucose 6-phosphate dehydrogenase and of 20-30% in the activities of the remaining enzymes of the pentose phosphate pathway; hexokinase activity was also decreased. Treatment with cortisone for 3 days did not significantly raise the activity from that found in adrenalectomized rats. Treatment of normal rats with high doses of cortisone had no significant effect on the activities of the enzymes of the pentose phosphate pathway in adipose tissue. 6. The changes in enzyme activities are discussed in relation to: (a) the concept of constant-proportion groups of enzymes; (b) the known changes in the flux of glucose through alternative metabolic pathways; (c) the pattern of change found in liver with similar hormonal and dietary conditions.
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PMID:The pentose phosphate pathway of glucose metabolism. Hormonal and dietary control of the oxidative nd non-oxidative reactions and related enzymes of the cycle in adipose tissue. 581 81

The enzyme phosphoglucose isomerase (PGI), phosphoglucomutase (PGM), hexokinase (HK), adenylate kinase (AK), fructokinase (FK), mannose-6-phosphate isomerase (MPI), glucose-6-phosphate dehydrogenase (G-6-PDH) and malate dehydrogenase (MDH) were chosen to study the variation between isolates, cercariae and adults, individuals, and sexes of Schistosoma mansoni and S. rodhaini, using horizontal polyacrylamide gel electrophoresis. The method described allows combinations of six of the eight enzymes to be scored in the homogenate from one adult worm. In adult S. mansoni one phenotype of the eight enzymes was observed in all isolates. In addition, the enzyme PGI showed polymorphism in the isolates from Tala, Kenya and Uganda. PGM in the isolates from Tala, Kenya and South Africa showed polymorphism. The cercarial phenotype differs from the adult phenotype in G-6-PDH, where the cercarial enzyme mobility is slower than that in the adult worm. The low amount of intrastrain variation observed in this species is explained by the limited amount of material used to establish the laboratory stocks, whereas the genetic similarity between geographically widely separated stocks does suggest that only limited geographical variation is likely to occur in S. mansoni. It is suggested that the gene controlling the PGI polymorphism is located on the sex chromosomes of S. mansoni. Mobility differences were observed between S. mansoni and S. rodhaini in the enzyme PGI and PGM, and these characteristics might be useful for a quick identification of schistosome cercariae emerging from Biomphalaria sp. in Africa.U
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PMID:Isoenzyme studies on cercariae from monoinfections and adult worms of Schistosoma mansoni (10 isolates) and S. rodhaini (one isolate) by horizontal polyacrylamide gel electrophoresis and staining of eight enzymes. 621


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