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)

Hexokinase from pyloric caeca of the starfish, Asterias amurensis, was purified to a specific activity of 148 units/mg protein. The purified enzyme appeared to be homogeneous on SDS-polyacrylamide gel electrophoresis. The molecular weight determined by SDS polyacrylamide gel electrophoresis and Ultrogel AcA 34 gel filtration was about 50,000. The enzyme showed a broad pH optimum ranging from 7.4 to 9.5. The Km values for D-glucose, D-fructose, 2-deoxy-D-glucose, D-mannose, D-glucosamine and ATP were 0.045, 4, 0.21, 0.05, 0.35 and 0.3 mM, respectively. N-Acetyl-D-glucosamine, D-xylose and D-galactose were not phosphorylated. The enzyme was strongly inhibited by the reaction products, glucose 6-phosphate and ADP, but not by high levels of D-glucose. The starfish hexokinase thus resembled mammalian isozyme A with respect to kinetic properties.
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PMID:Purification and properties of hexokinase from the starfish, Asterias amurensis. 89 76

In biopsy samples of the lateral part of the quadriceps femoris muscle of 6 obese diabetic male patients and of 11 obese males with a normal glucose tolerance, the activities of 7 enzymes of energy metabolism were estimated: hexokinase, cytoplasmic glycerol-3-phosphate: NAD dehydrogenase, triosephosphate dehydrogenase, lactate dehydrogenase, citrate synthase, malate dehydrogenase and 3-hydroxyacyl-CoA dehydrogenase. The obese diabetic male patients exhibited decreased activities of enzymes of carbohydrate breakdown and cytoplasmic NAD regeneration. Enzymes connected functionally with aerobic metabolism were less affected. The unchanged activity of 3-hydroxyacyl-CoA dehydrogenase points to an increased role of fatty acid catabolism in the muscle.
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PMID:Enzyme activities in quadriceps femoris muscle of obese diabetic male patients. 90 76

Human erythrocyte hexokinase (ATP: D-hexose 6-phosphotransferase, EC 2.7.1.1) was inhibited competitively with respect to MgATP2- by glucose-6-P (Ki - 10.8 muM) and fructose-6-P (Ki = 160 muM). Low concentrations of inorganic phosphate were competitive with respect to glucose-6-P and fructose-6-P, although higher concentrations of Pi were not able to overcome completely the inhibition by the hexose phosphates. The results are consistent with a model in which hexokinase exists in equilibrium either as free or phosphate-associated enzyme, the latter having a reduced but still substantial affinity for hexose phosphate. An alternative explanation could be found in the presence of two different enzymes, one with a high affinity for glucose-6-P being sensitive to regulation by Pi, one with a lower affinity for glucose-6-P being insensitive to Pi. A similar but less pronounced effect of Pi, was found on the inhibition by 2,3-diphosphoglycerate (Ki = 4.0 mM). Pi in the absence of inhibitor was also a competitive inhibitor with respect to MgATP2- (Ki = 20 mM). Furthermore a competitive inhibition with respect to MgATP2- was found by fructose 1,6-diphosphate (Ki = 4.3 mM), glycerate-3-P (Ki = 3.8 mM), glycerate-2-P (Ki = 12.5 mM), MgADP- (Ki = 1.0 mM) and MgAMP (Ki = 1.7 mM).
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PMID:Regulation of human erythrocyte hexokinase. The influence of glycolytic intermediates and inorganic phosphate. 91 66

Blood serum of oncologic patients due to immunoglobulin involved in its composition, activates glycolysis in the soluble fraction of muscles when using starch, glycogen and glucose as substrates. The activation is registered under both aerobic and anaerobic conditions. When elucidating the immunoglobulin effect in a glycolytic chain under aerobic conditions it is shown that its activating effect in the incomplete incubation system is manifested with such glycolysis substrates as fructose-6-phosphate and 2-phosphoglyceric acid. Glycolysis activation with serum is insignificant or absent at all with the presence of glucose-6-phosphate, fructose-1,6-diphosphate, 3-phosphoglyceric aldehide, 3-phosphoglyceric acid, phosphoenolpyruvic acid, sodium pyruvate. Immunoglobulin isolated from the blood serum of oncologic patients does not affect the activity of purified preparations of hexokinase, glycerinaldehydephosphate dehydrogenase, lactate dehydrogenase under aerobic and anaerobic conditions. When using the air as a gas medium lactate dehydrogenase is activated by immunoglobulin. Lactate dehydrogenase activity under aerobic and anaerobic conditions is essentially lower than in the case when the air serves as a gas medium.
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PMID:[Peculiarities of the action of protein positively reacting in the sedimentation test for cancer on the activity of glycolytic enzymes]. 92 7

The marked stimulatory effect of insulin on the conversion of 20 mM D-[6-14C]glucose to CO2, glyceride-glycerol, and fatty acid observed in small rat adipocytes was greatly diminished in large cells from older rats. Similarly, total glucose utilization as estimated by summing the total metabolites accumulated intracellularly plus the release of labeled CO2 and lactate was substantially lower in large cells in the presence of insulin and 5 mM labeled glucose. However, under conditions of 0.2 mM medium glucose where transport of the hexose into adipocytes is relatively more rate-limiting for subsequent metabolism, large cells actually utilized slightly greater total amounts of glucose than small cells in the presence of insulin. Increments of total glucose utilization due to both submaximal and maximal doses of insulin were similar in large and small cells incubated with a low glucose concentration. Under these conditions, conversion of labeled glucose to CO2 and fatty acid in response to insulin was somewhat diminished in large cells, while conversion to glyceride-glycerol was enhanced. The activity of the D-glucose transport system in large and small cells was estimated by monitoring initial rates and small cells was estimated by monitoring initial rates of 3-O-[3H]methylglucose uptake by a rapid filtration method. Transport system activity on a per cell basis was actually severalfold higher in large adipocytes in the basal state as well as in the presence of submaximal and maximal concentrations of insulin compared to small cells. However, the percent stimulation by insulin was less in the large cells. Uptake of 2-deoxyglucose under basal conditions and in response to insulin was also higher in large cells compared to small cells. Analysis of the accumulated label in extracts from fat cells incubated with D-[14C]deoxyglucose revealed the presence of free deoxyglucose, deoxyglucose-6-phosphate, and 6-phosphodeoxygluconate. The levels of these metabolites were significantly higher in large cells compared to small cells indicating hexokinase activity appears not to account for the defective glucose utilization in large cells at high glucose concentrations. It is concluded that (a) possible defects in insulin receptor components, the D-glucose transport system, and the coupling mechanism which links these entities do not significantly contribute to the apparent insulin-insensitivity of large fat cells and (b) the principal cellular defect which confers this blunted insulin response to large rat adipocytes involves one or more intracellular enzymes involved in glucose metabolism.
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PMID:Cellular basis of insulin insensitivity in large rat adipocytes. 93 92

The control of mitochondrial ATP synthesis by the extramitochondrial adenine nucleotide pattern was investigated with rat liver mitochondria. It is demonstrated that any stationary state between the two limit states of maximum activity (state 3) and of resting activity (state 4) can be obtained by a hexokinase-glucose trap as an ADP-regenerating system. These intermediate states are characterized by stationary respiratory rates, stationary redox levels of the cytochromes b and c and stationary levels of extramitochondrial ATP and ADP between the rates and levels of the limit states. At a constant concentration of inorganic phosphate the activity of mitochondria between the limit states is controlled by the extramitochondrial ATP/ADP ratio independent of the total concentration of adenine nucleotides present. The control range was found to be between ratios of about 5 and 100 at 10 mM phosphate. At lower ratios the mitochondria are in their maximum phosphorylating state. With succinate+rotenone and glutamate+malate the same control range was observed, indicating that it is independent of the nature of substrate oxidized. The results suggest that in the control range the mitochondrial activity is limited by the competition of ADP and ATP for the adenine nucleotide translocator.
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PMID:Control of oxidative phosphorylation by the extra-mitochondrial ATP/ADP ratio. 95 75

1. Human erythrocyte hexokinase (ADP:D-hexose 6-phosphotransferase, EC 2.7.1.1) was purified 50 000--100 000-fold with a final specific activity of about 25--50 units/mg protein using gel-filtration, ion-exchange chromatography and affinity chromagraphy. 2. After isoelectrofocusing ofthe preparation one major protein band could be detected besides a minor band. THe isoelectric point of the major protein band was found to be 4.7. 3. After purification the enzyme could be stabilized in a medium containing inorganic phosphate, glucose, glycerol and mercaptoethanol. 4. The molecular weight was determined by gel-filtration and was found to be 132 000+/-8000. 5. The enzyme shows a broad pH optimum ranging from 7.0 to 8.4. 6. The kinetic behavior of the purified enzyme at 37 degrees C was somewhat different from the normal Michaelis-Menten kinetics due to its instability. The affinity constants were 0.048--0.080 mM for glucose and 0.57--1.0 mM for Mg-ATP. 7. The enzyme was specific for Mg- ATP as the nucleotide substrate. Mg-UTP, Mg-ITP,Mg-GTP and Mg-CTP were not converted to corresponding diphosphates. Several hexoses could be phosphorylated by the enzyme. Mannose could be phosphorylated at the same rate as glucose, although the affinity for the enzyme was lower (5m=0.60mM). Much lower rates and lower affinities were found with 2-deoxy-D-glucose (5m=1.0mM), D(+)-glucosamine (5m=4.5 mM) and fructose (5m=10 mM). N-acetyl-D-glucosamine , galactose andsorbose were not phosphorylated at all.
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PMID:Purification and some properties of human erythrocyte hexokinase. 95 36

In soluble fraction of rat liver studies have been made on the activity of glycolytic enzymes and dehydrogenases of the pentose phosphate pathway 3 and 20 hours after the electrical stimulation of the medial (HVM) and lateral (AHL) structures of the medial hypothalamus via chronically implanted electrodes. Electrical stimulation of the HVM within 3 hours decreased total hexokinase, glucose-6-phosphate dehydrogenase, and lactate dehydrogenase activities, and to a lower extent -- the activity of glucokinase. This effect was not prevented by the adrenalectomy. During stimulation of the AHL, the decrease of LDH activity was the same, whereas the activity of hexokinase, glucose-6-phosphate dehydrogenase and glucokinase decreased to a lower extent. Electrical stimulation of the medial hypothalamus within 20 hours decreased the response, this effect being presumably associated with the decrease in the content of endogenous noradrenalin in the liver of animals. The role of the hypothalamus and sympathetic nervous system in regulation of the investigated enzymes of energy metabolism in the liver is discussed.
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PMID:[Participation of the hypothalamus in regulating the activity of rat liver energy metabolism enzymes]. 98 65

The activities of glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate: NADP oxidoreductase, G6PD), 6 phosphate glucono dehydrogenase (6 phospho-D-gluconate: NADP oxidoreductase, 6PGD) lactate dehydrogenase (D-lactate: NAD oxidoreductase, LDH), glutamate oxaloacetate transaminase (L-aspartate: 2-oxo-glutarate aminotransferase, GOT) and hexokinase (ATP: D-hexo-6-phosphotrans-ferase, Hx) were measured over 24 h in isolated lymphocytes of normal subjects and in white cells of patients with chronic lymphatic leukaemia (CLL). The activitty patterns of all enzymes in the normal lymphocytes were similar. A computed pattern of all the results exhibited a circadian rhythm of activity with the highest level at 16.00 hours. The oscillations in the activities of the same enzymes in the CLL cells differed among the patients, although all the enzymes of the same individual showed a similar diurnal rhythmic pattern. All peaks in this group appeared between 20.00 and 08.00 hours. The possible importance of these observations in setting up therapeutic schedules was raised.
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PMID:Blood leucocyte enzymes. III. Diurnal rhythm of activity in isolated lymphocytes of normal subjects and chronic lymphatic leukaemia patients. 98 50

In extracts of rabbit bone marrow cells was studied effect of erythropoietine on the activity of some enzymes (hexokinase, phosphoglucomutase, phosphohexoisomerase, lactate dehydrogenase, glucoso-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and NADP-reductase). The NADP-reductase activity was increased under the effect of erythropoietine; the activities of other enzymes studied was not altered.
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PMID:[Study of the mechanism of erythropoietin effect on energy metabolism in the bone marrow]. 103 Aug 78


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