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)

The maximum activities of some key enzymes of metabolism were studied in lungs of fed and 48-h-starved rats. The maximum activity of hexokinase in the lung is similar to that of other tissues of the body, but lower than that of phosphorylase and 6-phosphofructokinase. High activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were found in lung tissue, suggesting the importance of the pentose phosphate pathway in the lung. The activities of hexokinase and 6-phosphofructokinase were decreased whereas that of phosphorylase increased in response to starvation. Of the enzymes of the tricarboxylic acid cycle whose activities were measured, that of oxoglutarate dehydrogenase was the lowest, yet its activity (approximately 4.2 nmol/min per mg protein at 37 degrees C) was considerably greater than the flux through the cycle (0.46 nmol/min per mg protein at 37 degrees C; calculated from oxygen consumption by incubated lung slices). The activities of both oxoglutarate dehydrogenase and citrate synthase were decreased by starvation. The activities of 3-oxoacid CoA-transferase and acetoacetyl-CoA thiolase were low in lung tissue compared to those of other tissues (eg kidney, brain) and that of 3-hydroxybutyrate dehydrogenase was very low. The activity of carnitine palmitoyl transferase is higher in the lung, suggesting that fatty acids (and possibly acetoacetate) could provide acetyl-CoA as substrate for the tricarboxylic acid cycle. Very low rates of utilization of 3-hydroxybutyrate were observed during incubation of lung slices, but that of oleate was 1.2 nmol/h per mg of protein.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Metabolism of glucose, glutamine, long-chain fatty acids and ketone bodies by lungs of the rat. 176

1. A comparative study was carried out on blood glucose partition and glucose metabolism of penguin erythrocytes and somatic tissues. Pygoscelidae penguins (Pygoscelis antarctica and P. papua) were used in these experiments. 2. Blood glucose partition was established by assaying whole blood and plasma glucose in several individuals of the gentoo and chinstrap penguins. 3. It was found that almost all the whole blood sugar is compartmentalized at the plasma site, the red blood cells being ineffective in regard to glucose metabolism. 4. Levels of hexokinase, phosphoglucose isomerase, phosphofructokinase, fructose bisphosphate aldolase, glyceraldehyde phosphate dehydrogenase, phosphoglycerate kinase, phosphopyruvate hydratase (enolase), pyruvate kinase, alpha-glycerolphosphate dehydrogenase and fructose bisphosphate phosphatase were estimated in the erythrocytes of both gentoo and chinstrap penguins, the same determinations being carried out also on the somatic tissues (leg muscle, breast muscle, heart muscle, liver and brain) of the gentoo.
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PMID:Blood glucose partition and levels of glycolytic enzymes in erythrocytes and somatic tissues of penguins. 292 38

In order to test the possible involvement of surface proteins on some metabolical aspects of chick glial cell differentiation in culture, perturbations were induced on the glial cell surface membrane by limited trypsinization before seeding. The developmental changes of enzymes involved in the energy metabolism of the cell: malate dehydrogenase (MDH), glutamate dehydrogenase (GDH), hexokinase (HK), lactate dehydrogenase (LDH), enolase as well as glutamine synthetase (GS) were determined in trypsin treated cells and controls. The total protein and DNA content per dish was higher in treated cells than in controls, however the protein ratio towards DNA remained unchanged. The levels of GS, GDH, LDH, and enolase activities were significantly enhanced after trypsin treatment of the cells compared to controls. The enhanced value of total LDH activity is essentially the result of the increase of M subunit containing isoenzymes. Considering that a higher level of GS activity characterizes some maturation of the glial cells (as observed during the maturation of the chick brain) it is apparent that modifications of cell surface located factors, by trypsin treatment, induce differentiation phenomena at the functional state of the glial cells in culture. This may indicate that interactions located at the cell surface are involved in the modulation of key enzymes of the energy metabolism pathway.
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PMID:Trypsinization of chick glial cells before seeding: effects on energy metabolism enzymes and glutamine synthetase. 614 Jun 46

The development of key enzyme activities concerned with glucose metabolism was studied in six regions of the rat brain in animals from just before birth (-2 days) through the neonatal and suckling period until adulthood (60 days old). The brain regions studied were the cerebellum, medulla oblongata and pons, hypothalamus, striatum, mid-brain and cortex. The enzymes whose developmental patterns were investigated were hexokinase (EC 2.7.1.1), aldolase (EC 4.1.2.13), lactate dehydrogenase (EC 1.1.1.27) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49). Hexokinase, aldolase and lactate dehydrogenase activities develop as a single cluster in all the regions studied, although the timing of this development varies from region to region. Glucose-6-phosphate dehydrogenase activity, however, declines relative to glycolytic enzyme activity as the brain matures. When the different brain regions are compared, it is clear that the medulla develops its glycolytic potential, as indicated by its potential enzyme activity, considerably earlier than the other regions (hypothalamus, striatum and mid-brain), with the cortex and cerebellar activities developing even later. This enzyme developmental sequence correlates well with the neurophylogenetic development of the brain and adds support to the hypothesis that the development of the potential for glycolysis in the brain is a necessary prerequisite for the development of neurological competence.
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PMID:Regional enzyme development in rat brain. Enzymes associated with glucose utilization. 671 9

Gut fuel utilisation has several unique features. Arterial and luminal fuels provide nutrition for the enterocyte, the former being of more importance. This factor, and the heterogeneity of cell types within the gut makes it difficult to define its fuel utilisation. Metabolic control logic suggests that modulation of the maximal activity of any pathway resides in those enzymes that operate in vivo at rates far below their maximal capacity and that catalyse non-equilibrium reactions. On this basis, although enterocyte hexokinase activity is much higher than in other 'glycolytic' cells (for example, brain), potentially high rates of glucose utilisation are modulated by substrate cycling of glucose 6-phosphate back to glucose through glucose 6-phosphatase. Glutamine metabolism proceeds by glutaminase to produce glutamate, which may then be transaminated (aspartate-aminotransferase and alanine-amino transferase) to produce alpha-ketoglutarate, alanine, and aspartate. The end products of glutamine metabolism by incubated gut preparations in vitro (mainly alanine), suggests that enterocytes, not immune cells, are responsible for most gut glutamine metabolism. High flux rates of glucose and glutamine metabolism in the enterocyte may result from the need for de novo synthesis of purines and pyrimidines and ribose sugars for nucleic acid synthesis. Sepsis reduces rates of glucose and glutamine metabolism, perhaps to preserve the increased consumption of these fuels by activated lymphocytes and macrophages in the gut wall.
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PMID:Quantitative aspects of glucose and glutamine metabolism by intestinal cells. 812 83

The presence of glycogen in astroglia-rich primary cultures derived from the brains of newborn rats depends on the availability of glucose in the culture medium. On glucose deprivation, glycogen vanishes from the astroglial cultures. This decrease of glycogen content is completely prevented if 2-deoxyglucose in a concentration of > 1 mM or 1,5-gluconolactone (20 mM) is present in the culture medium. 2-Deoxyglucose itself or 3-O-methylglucose, a glucose derivative that is not phosphorylated by hexokinase, does not reduce the activity of glycogen phosphorylase purified from bovine brain or in the homogenate of astroglia-rich rat primary cultures. In contrast, deoxyglucose-6-phosphate strongly inhibits the glycogen phosphorylase activities of the preparations. Half-maximal effects were obtained at deoxyglucose-6-phosphate concentrations of 0.75 (phosphorylase a, astroglial culture), 5 (phosphorylase b, astroglial culture), 2 (phosphorylase a, bovine brain), or 9 mM (phosphorylase b, bovine brain). Thus, the block of glycogen degradation in these cells appears to be due to inhibition of glycogen phosphorylase by deoxyglucose-6-phosphate rather than deoxyglucose itself. These results suggest that glucose-6-phosphate, rather than glucose, acts as a physiological negative feedback regulator of the brain isoenzyme of phosphorylase and thus of glycogen degradation in astrocytes.
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PMID:Inhibition by 2-deoxyglucose and 1,5-gluconolactone of glycogen mobilization in astroglia-rich primary cultures. 845 36

While studying the delivery of cytoplasmic proteins to the presynaptic terminals of CNS neurons, we discovered unique characteristics of one protein (p118) conveyed in slow component b (SCb) of axonal transport, the large group of proteins representing the cytoplasmic matrix. Alone among the SCb group, p118 coisolated with the synaptic junctional complex on biochemical fractionation of the radiolabeled synaptic regions. Purification and amino acid sequencing of this protein revealed it is most likely the guinea pig form of type I (brain) hexokinase (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1). Further biochemical treatments were consistent with this identity. The majority of type I brain hexokinase has been thought to be associated primarily with membranes, in particular the mitochondrial outer membrane. We found that the majority of type I hexokinase is transported toward the terminals at a rate at least 10 times slower than that exhibited by the maximal or average rate of mitochondria. This suggests that, in the axon, the enzyme exhibits transient or dynamic interactions with mitochondria that are moving more rapidly. It is not clear whether hexokinase binds exclusively to mitochondria, or also exhibits association with nonmitochondrial membranes. The unexpected enrichment of hexokinase during synaptic junctional complex purification may result from its strong association with the presynaptic membrane portion of the synapse.
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PMID:Type I brain hexokinase: axonal transport and membrane associations within central nervous system presynaptic terminals. 876 15

To clarify the relationship between cerebral glucose metabolic rate constants and glucose-metabolizing enzyme activities in the cerebral cortex, we evaluated the cerebral metabolic rate of glucose (CMRGlu), metabolic rate constants of [18F]-2-fluoro-2-deoxy-D-glucose (FDG) and related enzyme activities in the frontal cortex under normal and glucose metabolism-suppressed conditions. Applying a three-compartment four-parameter model, metabolic rate constants were obtained by dynamic positron emission tomography with FDG, and CMRGlu was calculated based on these rate constants. The glycolytic enzyme activities were determined by in vitro biochemical assay. Three days after ibotenic acid injection into the basal forebrain, CMRGlu was decreased in the ibotenic acid-treated frontal cortex as well as k3* (phosphorylation), while K1* (plasma to brain) showed no remarkable change. No significant reductions of the enzyme activities except for hexokinase activity were found in the frontal cortex. Regression analysis showed a significant positive correlation between k3* and the hexokinase activity. These results suggested that k3* in the compartment analysis reflects hexokinase activity.
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PMID:Compartment analysis of cerebral glucose metabolism and in vitro glucose-metabolizing enzyme activities in the rat brain. 882 66

Quantitative imaging of glucose metabolism of human brain tumors with PET utilizes 2-[(18)F]-fluorodeoxy-D-glucose (FDG) and a conversion factor called the lumped constant (LC), which relates the metabolic rate of FDG to glucose. Since tumors have greater uptake of FDG than would be predicted by the metabolism of native glucose, the characteristic of tumors that governs the uptake of FDG must be part of the LC. The LC is chiefly determined by the phosphorylation ratio (PR), which is comprised of the kinetic parameters (Km and Vmax) of hexokinase (HK) for glucose as well as for FDG (LC proportional to (Km(glc) x Vmax(FDG))/(Km(FDG) x Vmax(glc)). The value of the LC has been estimated from imaging studies, but not validated in vitro from HK kinetic parameters. In this study we measured the kinetic constants of bovine and 36B-10 rat glioma HK I (predominant in normal brain) and 36B-10 glioma HK II (increased in brain tumors) for the hexose substrates glucose, 2-deoxy-D-glucose (2DG) and FDG. Our principal results show that the KmGlc < KmFDG << Km2DG and that PR2DG < PRFDG. The FDG LC calculated from our kinetic parameters for normal brain, possessing predominantly HK I, would be higher than the normal brain LC predicted from animal studies using 2DG or human PET studies using FDG or 2DG. These results also suggest that a shift from HK I to HK II, which has been observed to increase in brain tumors, would have little effect on the value of the tumor LC.
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PMID:Kinetic characterization of hexokinase isoenzymes from glioma cells: implications for FDG imaging of human brain tumors. 1129 20

The Indian traditional system of medicine prescribed plant therapies for diseases including diabetes mellitus called madhumeh in Sanskrit. One such plant mentioned in Ayurveda is Pterocarpus marsupium (PM). In the present study, aqueous extract of PM (1 g/kg PO) was assessed for its effect on glycogen levels of insulin dependent (skeletal muscle and liver), insulin-independent tissues (kidneys and brain) and enzymes such as glucokinase (GK), hexokinase (HK), and phosphofructokinase (PFK). Administration of PM led to decrease in blood glucose levels by 38 and 60% on 15th and 30th day of the experiment. Liver and 2-kidney weight expressed as percentage of body-weight was significantly increased in diabetics (p < 0.0005) vs. normal controls and this alteration in the renal weight (p < 0.0005) but not liver weight was normalized by feeding of PM extract. Renal glycogen content increased by over 10-fold while hepatic and skeletal muscle glycogen content decreased by 75 and 68% in diabetic controls vs. controls and these alteration in glycogen content was partly prevented by PM. Activity of HK, GK and PFK in diabetic controls was 35,50 and 60% of the controls and PM completely corrected this alteration in PFK and only partly in HK and GK.
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PMID:Effect of feeding aqueous extract of Pterocarpus marsupium on glycogen content of tissues and the key enzymes of carbohydrate metabolism. 1248 25


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