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 improved method has been developed for the assay of hexokinase (EC 2.7.1.1) levels in human tissue homogenates. The enzyme is quantitated by the spectrophotometric measurement, at 340 nm, of NADPH formed according to the reaction scheme: [formula: see text] In tissue homogenates a number of enzymes are present which can interfere with the assay by reacting with substrates or products of the assay reactions. In the described procedure hexokinase is assayed directly in homogenates under conditions in which the effect of possible contaminating enzymes (glucose dehydrogenase, EC 1.1.1.47; glucose 6-phosphatase, EC 3.1.3.9; glucose phosphate isomerase, EC 5.3.1.9; 6-phosphogluconate dehydrogenase EC 1.1.1.44; and NADP-reducing enzymes) are eliminated. Precision studies on the assay gave within-day reproducibility of 4.3% (CV) on a tissue having a mean activity of 1.68 U/g of tissue, and day-to-day variability of 15% (CV) for a tissue averaging 1.83 U/g of tissue.
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PMID:An improved assay for hexokinase activity in human tissue homogenates. 976 31

1. Differential molecular sieving is the concept applied to bring together isoenzymes of ATP:D-hexose-6-phosphotransferase (hexokinases) with glucose 6-phosphate dehydrogenase in acrylamide gels by utilization of their dissimilar electrophoretic mobilities. 2. The hexokinase isoenzymes migrate and separate in gels with pore sizes selected to entrap glucose 6-phosphate dehydrogenase in their interstices. The locations of the bands of specific activity are visualized by fluorescence of NADPH under long wave, ultraviolet radiation. 3. A new discontinuous electrochemical system has been devised to deliver protective thiol groups into the gel. Cysteine (trailing ion) and SO4(2-) (leading ion) form a sharp moving boundary. 4. The high resolution of the system has permitted visualization of a rapidly migrating, high Km hexokinase in murine spleen, fat, kidney and lymph nodes. Hexokinase Types I and II, were observed in all tissues tested, but Type IV was seen only in the liver. 5. The importance of glucose concentration effects on hexokinase activity is emphasized by inactivation of slowly migrating low Km hexokinase Types I and II following exposure to 200 mM glucose during preparation of extracts.
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PMID:Differential molecular sieving permits visualization of hexokinase isoenzymes following electrophoretic separation in high resolution acrylamide gels. 1145 84

Gliadins and glutenins, the major storage proteins of wheat endosperm (Triticum durum, Desf. cv Monroe), were reduced in vitro by the NADP/thioredoxin system (NADPH, NADP-thioredoxin reductase and thioredoxin; in plants, the h type) from either the same source or the bacterium Escherichia coli. A more limited reduction of certain members of these protein groups was achieved with the reduced form of glutathione or glutaredoxin, a protein known to replace thioredoxin in certain bacterial and mammalian enzyme systems but not known to occur in higher plants. Endosperm extracts contained the enzymes necessary to reduce NADP by the oxidative pentose phosphate pathway (hexokinase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase). The gliadins and glutenins were also reduced in vivo during germination--an event that accompanied their proteolytic breakdown. The results suggest that thioredoxin, reduced by NADPH generated via the oxidative pentose phosphate pathway, functions as a signal in germination to enhance metabolic processes such as the mobilization of storage proteins and, as found earlier, the activation of enzymes.
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PMID:Specific reduction of wheat storage proteins by thioredoxin h. 1153 80

Activities of hexokinase (HK), glucose-6-phosphate dehydrogenase (G6PDH), fructose-6-phosphate kinase (F6PK), glutamate dehydrogenase (GlutDH), aspartate aminotransferase (AAT), malate dehydrogenase (MDH) and glycerol-3-phosphate dehydrogenase (GPDH) were determined in tissue extracts of testes and ovaries of adult Dipetalogaster maximus (Uhler) and Triatoma infestans (Klug) (Hemiptera: Reduviidae), insect vectors of Chagas disease. The fine structure organization of the same organs were studied by electron microscopy. Results allow the following inferences: in testes from both species, most of the glucose would be utilized through the glycolytic pathway. Amino acid catabolism for energy purposes appears to be unimportant. The number of mitochondria and the development of the rough endoplasmic reticulum in cells of the spermatogenic line indicate the occurrence of active oxidative metabolism and protein synthesis; in ovaries, levels of G6PDH indicate the existence of an active pentose pathway which would supply the NADPH required for fat and ecdysteroid synthesis. Amino acid catabolism appears to be relatively more important in ovary than in testis. Fat and glycogen are stored in follicular cells of D. maximus; oocytes of both species contain numerous fat droplets. Abundant mitocondria are present in follicular cells and oocytes. A well developed rough endoplasmic reticulum and free ribosomes are also conspicuous in these cells. The malate/aspartate H-transfer system seemed to be relatively more important than the glycerophosphate shuttle in ovaries as well in testes.
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PMID:Comparative study of enzymes in testes and ovaries from adult Dipetalogaster maximus (Uhler) and triatoma infestans (Klug) (Hemiptera: Reduviidae). correlation with fine structural organization. 1175 15

We have recently reported on the activities of glucose-6-phosphate dehydrogenase (G6PD), hexokinase (HK) and carbonic anhydrase I (CA-I) and II (CA-II) isoenzymes obtained from erythrocytes of healthy subjects and untreated patients with hyperthyroid diseases. Also, erythrocyte zinc concentrations were measured. Red blood cell (RBC) zinc (Zn) concentration was measured by atomic absorption spectrophotometry. Activities of carbonic anhydrase II and I isoenzymes were determined with CO2-hydratase activity method by using selective inactivation with bromopyruvate. G6PD and HK enzyme activities were measured spectrophotometrically via absorbance change (at 340 nm) in NADPH formed as a result of the reactions catalysed by these enzymes. In statistical analysis of all these parameters, activity of CA-I was 4388 +/- 207 (EU/gHb) and 2881 +/- 869 (EU/gHb) in healthy and untreated hyperthyroid subjects, respectively. The activity values for CA-II were 5391 +/- 257 (EU/gHb) and 4688 +/- 12.6 (EU/gHb) in healthy and untreated hyperthyroid subjects. Glucose 6-phosphate dehydrogenase (G6PD) activity was 10.19 +/- 1.87 (EU/gHb) in healthy group and 4.92 +/- 2.49 (EU/gHb) in patient group. While hexokinase enzyme activity was 1.575 +/- 0.898 in healthy subjects, it was 0.651 +/- 0.418 (EU/gHb) in the patient group. While erythrocyte zinc concentration in the healthy subjects was 49.32 +/- 23.5 (mg/gHb), this concentration for patients with uncontrolled hyperthyroid diseases was significantly decreased to 29.62 +/- 4.26 (mg/gHb). As a conclusion, CA-I isoenzyme, G6PD, hexokinase activities and erythrocyte zinc concentration had decreased in untreated patients carrying hyperthyroid diseases as compared to those of the healthy subjects.
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PMID:Investigation of red blood cell carbonic anhydrase, glucose 6-phosphate dehydrogenase, hexokinase enzyme activities, and zinc concentration in patients with hyperthyroid diseases. 1210 90

The serine/threonine kinase Akt is a component of many receptor signal transduction pathways and can prevent cell death following growth factor withdrawal. Here, we show that Akt inhibition of cell death is not dependent on new protein translation. Instead, Akt inhibition of cell death requires glucose hydrolysis through glycolysis. Akt was found to regulate multiple steps in glycolysis via posttranscriptional mechanisms that included localization of the glucose transporter, Glut1, to the cell surface and maintenance of hexokinase function in the absence of extrinsic factors. To test the role of glucose uptake and phosphorylation in growth factor-independent survival, cells were transfected with Glut1 and hexokinase 1 (Glut1/HK1) cells. Glut1/HK1 cells accumulated Glut1 on the cell surface and had high glucose uptake capacity similar to that of cells with constitutively active Akt (mAkt). Unlike mAkt-expressing cells, however, they did not consume more glucose, did not maintain prolonged phosphofructokinase-1 protein levels and activity, and did not maintain pentose phosphate shuttle activity in the absence of growth factor. Nevertheless, expression of Glut1 and HK1 promoted increased cytosolic NADH and NADPH levels relative to those of the control cells upon growth factor withdrawal, prevented activation of Bax, and promoted growth factor-independent survival. These data indicate that Bax conformation is sensitive to glucose metabolism and that maintaining glucose uptake and phosphorylation can promote cell survival in the absence of growth factor. Furthermore, Akt required glucose and the ability to perform glycolysis to prevent Bax activation. The prevention of Bax activation by posttranscriptional regulation of glucose metabolism may, therefore, be a required aspect of the ability of Akt to maintain long-term cell survival in the absence of growth factors.
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PMID:Akt-directed glucose metabolism can prevent Bax conformation change and promote growth factor-independent survival. 1451

This study was conceived in an effort to understand cause and effect relationships between hyperglycemia and diabetic retinopathy. Numerous studies show that hyperglycemia leads to oxidative stress in the diabetic retinas, but the mechanisms that generate oxidative stress have not been resolved. Increased electron pressure on the mitochondrial electron transfer chain, increased generation of cytosolic NADH, and decreases in cellular NADPH have all been cited as possible sources of reactive oxygen species and nitrous oxide. In the present study, excised retinas from control and diabetic rats were exposed to euglycemic and hyperglycemic conditions. Using a microwave irradiation quenching technique to study retinas of diabetic rats in vivo, glucose, glucose-derived metabolites, and NADH oxidation/reduction status were measured. Studying excised retinas in vitro, glycolytic flux, lactate production, and tricarboxylic acid cycle flux were evaluated. Enzymatically assayed glucose 6-phosphate and fructose 6-phosphate were only slightly elevated by hyperglycemia and/or diabetes, but polyols were increased dramatically. Cytosolic NADH-to-NAD ratios were not elevated by hyperglycemia nor by diabetes in vivo or in vitro. Tricarboxylic acid cycle flux was not increased by the diabetic state nor by hyperglycemia. On the other hand, small increases in glycolytic flux were observed with hyperglycemia, but glycolytic flux was always lower in diabetic compared with control animals. An observed decrease in activity of glyceraldehyde-3-phosphate dehydrogenase may be partially responsible for slow glycolytic flux for retinas of diabetic rats. Therefore, it is concluded that glucose metabolism, downstream of hexokinase, is not elevated by hyperglycemia or diabetes. Metabolites upstream of glucose such as the sorbitol pathway (which decreases NADPH) and polyol synthesis are increased.
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PMID:Analysis of glucose metabolism in diabetic rat retinas. 1638 Mar 92

Using isolated spinach (hybrid 424) chloroplasts deprived of their envelopes (reconstituted chloroplast system), the metabolism of glucose, glucose 1-phosphate, and glucose 6-phosphate via the oxidative pentose phosphate cycle was analyzed. The activity of oxidative pentose phosphate cycle was monitored by continuous sampling of the CO(2) released during the decarboxylation process of 6-phosphogluconate.The rate of CO(2) released in the dark from [C-1-(14)C]glucose 6-phosphate was 4 to 6 micromoles per milligram chlorophyll per hour. A CO(2) release from the C-6 position of [C-6-(14)C]glucose 6-phosphate was hardly measurable within 60 minutes of incubation. Glucose 1-phosphate was readily converted to glucose 6-phosphate without externally added glucose bisphosphate and was metabolized via the oxidative pentose phosphate cycle. The phosphorylation of glucose to glucose 6-phosphate was mediated by hexokinase present in the reconstituted system. This step was rate-limiting for the over-all reaction of the oxidative pentose phosphate cycle with glucose being the substrate (0.5 micromoles per milligram chlorophyll per hour). Addition of hexokinase increased the rate of CO(2) release to 5 micromoles per milligram chlorophyll per hour.The flow of carbon through the oxidative pentose phosphate cycle was greatly reduced upon the addition of NADPH and ATP. Whereas NADPH inhibited the metabolism of [C-1-(14)C]glucose 6-phosphate via the oxidative pentose phosphate cycle, ATP stimulated carbon flow into the 3-phosphoglycerate, dihydroxyacetone phosphate, and bisphosphates pools via the glycolytic pathway mediated by phosphofructokinase. This regulatory phenomenon could also be demonstrated with the reconstituted system undergoing a dark-light-dark transition. Data are presented indicating the conditions under which glucose 6-phosphate or glucose 1-phosphate are metabolized via the oxidative pentose phosphate cycle and the glycolytic pathway.
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PMID:Metabolism of Specifically Labeled Glucose, Glucose 1-Phosphate, and Glucose 6-Phosphate via the Oxidative Pentose Phosphate Cycle in a Reconstituted Spinach Chloroplast System in Darkness and in the Light. 1666 99

Chlorella strain (UTEX 27) maintains optimal photosynthetic capacity when growing photoautotrophically in the presence of ammonium. Nitrate-grown photoautotrophic cells, however, show a drastic loss of chlorophyll content and ribulose-1,6-bisphosphate carboxylase/oxygenase activity, resulting in a greater than 10-fold decrease in photosynthetic capacity and growth rate. Nitrate-grown cells are not deficient in protein content, and under mixotrophic and heterotrophic conditions, the alga can utilize nitrate as well as it does ammonium. The alga metabolizes both glucose and acetate in the dark with a doubling time of 5 to 6 hours. However, its growth on acetate is inhibited by light. Ribulose-1,6-biphosphate carboxylase/oxygenase activity correlates well with photosynthetic capacity, and glucose 6-phosphate dehydrogenase and hexokinase activities are altered in a manner consistent with the availability of glucose in growing cells. The alga appears to assimilate ammonium under photoautotrophic conditions primarily via the glutamine synthetase pathway, and shows an induction of both NADH and NADPH dependent glutamate dehydrogenase pathways under mixotrophic and heterotrophic conditions. Multiple isoforms are present only for hexokinase and glucose 6-phosphate dehydrogenase. Etiolated nitrate-grown cells resume greening and increase their photosynthetic capacity after about 6 hours of incubation in the presence of ammonium under photoautotrophic conditions. Similarly, the loss of photosynthetic capacity in ammonium-grown photoautotrophic cells commence about 9 hours after their transfer to heterotrophic nitrate containing media.
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PMID:Regulation of Chloroplast Development by Nitrogen Source and Growth Conditions in a Chlorella protothecoides Strain. 1666 75

Environmental factors such as solar radiation and drug treatment are potential cataractogenic agents. It is suggested that their damaging effects accumulate with age. The purpose of the study was to isolate the effect of one factor (UV-radiation) and find out the mechanism by which UV radiation causes damage to the eye lens. We irradiated bovine lenses with UV-A (365 nm) radiation for 50, 75, 90, 100, and 120 min and followed the optical changes of the lenses in a long-term organ culture. Enzyme activities were analyzed in lens epithelium after five days of incubation in organ culture. The enzymes analyzed were ATPase, which belongs to the transport mechanism in lens epithelium cells, hexokinase, the key enzyme of the glycolysis pathway, G6PD, which provides NADPH to the glutathione system and catalase, which protects the cells from H(2)O(2). Optical damage was observed even for the minimal radiation. The same amount of radiation also affected ATPase and hexokinase activities. G6PD and catalase were affected only in lenses which received radiation for 90 min, We can conclude that enzymes involved in the transport mechanism and metabolism are more sensitive to UV-A (365 nm) radiation than enzymes involved in the defense mechanism against oxidation.
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PMID:Long-term organ culture system to study the effect of UV-radiation on lens enzymes. 1864 67


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