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)

Human red blood cell hexokinase exists in multiple molecular forms with different isoelectric points but similar kinetic and regulatory properties. All three major isoenzymes (HK Ia, Ib, and Ic) are inhibited competitively with respect to Mg.ATP by glucose 6-phosphate (Ki = 15 microM), glucose 1,6-diphosphate (Ki - 22 microM), 2,3-diphosphoglycerate (Ki = 4 mM), ATP (Ki = 1.5 mM), and reduced glutathione (Ki = 3 mM). All these compounds are present in the human erythrocyte at concentrations able to modify the hexokinase reaction velocity. However, the oxygenation state of hemoglobin significantly modifies their free concentrations and the formation of the Mg complexes. The calculated rate of glucose phosphorylation, in the presence of the mentioned compounds, is practically identical to the measured rate of glucose utilization by intact erythrocytes (1.43 +/- 0.15 mumol h-1 ml red blood cells-1). Hexokinase in young red blood cells is fivefold higher when compared with the old ones, but the concentration of many inhibitors of the enzyme is also cell age-dependent. Glucose 6-phosphate, glucose 1,6-diphosphate, 2,3-diphosphoglycerate, ATP, and Mg all decay during cell ageing but at different rates. The free concentrations and the hemoglobin and Mg complexes of both ATP and 2,3-diphosphoglycerate with hemoglobin in the oxy and deoxy forms have been calculated. This information was utilized in the calculation of glucose phosphorylation rate during cell ageing. The results obtained agree with the measured glycolytic rates and suggest that the decay of hexokinase during cell ageing could play a critical role in the process of cell senescence and destruction.
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PMID:Regulatory properties of human erythrocyte hexokinase during cell ageing. 387 7

Results for urinary glucose by the Boehringer Mannheim BM33071 test pad and a hexokinase-based method agree well. The new test, which involves the glucose oxidase/peroxidase reaction, measures as little as 260 mg of glucose per liter. Acetoacetate, beta-hydroxybutyrate, and human hemoglobin do not interfere.
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PMID:New test for urinary glucose (BM33071) evaluated. 396 21

In rat erythrocyte homogenates, the phosphorylation of D-glucose measured at 30 degrees C over a wide range of glucose concentrations (50 microM to 20 mM) yielded in a double reciprocal plot a single straight line with a Km close to 0.06 mM and a maximal velocity close to 47 nmol/60 min per mg hemoglobin. At 8 degrees C, the rate of glucose phosphorylation was 60% higher in the presence of beta-D-glucose than alpha-D-glucose. Yet, in intact erythrocytes incubated at 8 degrees C in the presence of beta-D-glucose (4 or 7 mM), the glucose-induced increment in lactic acid output represented no more than 39 to 74% of that found in the presence of alpha-D-glucose. Thus, a greater rate of glycolysis in the presence of alpha-D-glucose was observed in a cell devoid of glucokinase and containing a hexokinase with preference for beta-D-glucose. These findings indicate that the anomeric specificity of glycolysis in intact cells cannot be predicted and does not necessarily depend on the anomeric preference of glucose-phosphorylating enzyme(s).
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PMID:Anomeric specificity of glycolysis in a non glucokinase-containing cell. 399 34

The action and some properties of cathepsin D, partly purified from unfertilized loach eggs, embryos and skeletal muscles were determined. The enzyme from embryo cells displays the activity maximum at pH 3.0 and pH 4.8 while enzyme from skeletal muscles--only at pH 3.0. Cathepsin D purified from all three sources splits actively hemoglobin, albumin, alpha-glycerophosphate dehydrogenase, pyruvate kinase and practically does not influence casein, hexokinase, glucose-6-phosphate dehydrogenase. The enzyme is comparatively thermolabile and its activity decreases in the presence of thiol compounds. The main part of cathepsin D in skeletal muscle cells and in embryo cells is precipitated after differential centrifugation of homogenates (25000 g; 60 min).
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PMID:[Properties of cathepsin D from unfertilized eggs, embryos and skeletal muscles of the loach]. 404 Jun 74

We instructed pregnant women with insulin dependent diabetes mellitus (IDDM) or noninsulin dependent diabetes mellitus (NIDDM) how to monitor their own blood glucose concentrations and evaluated the efficiency and feasibility of continuous subcutaneous insulin infusion (CSII) therapy. Self-monitored glucose concentrations with a reflectance meter correlated with those of hospital laboratory measurements (hexokinase method) with a coefficient of more than 0.9. Glycosylated hemoglobin (HbA1) levels of the patients were normalized with insulin treatment based on the self-monitored glucose concentrations. In pregnant women with NIDDM who monitored their blood glucose concentrations before breakfast, the fasting glucose concentrations could be lowered by insulin administration and the duration of hospitalization could be shortened compared to non-monitored patients. Although diurnal variations were prominent in pregnant women with IDDM and precise control of their blood glucose concentrations was difficult with conventional insulin administration, even if the patients had monitored their glucose concentrations 7 times a day, the mean glucose concentrations and M values could be kept in the optimum range in patients treated with CSII. These methods have contributed to the improvement in maternal and infant complications.
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PMID:[Assessment of self monitoring of blood glucose (SMBG) and continuous subcutaneous insulin infusion (CSII) in diabetic pregnant women]. 408 5

A method has been developed for measuring the adhesion of platelets to purified collagen fibers obtained from bovine tendon. This method differs from others in that: (a) platelet adhesion is measured in the absence of platelet aggregation; (b) platelet-rich plasma collected in ACD (acid citrate dextrose) or EDTA, or washed platelets can be employed; (c) adherent platelets are enumerated directly; (d) erythrocytes and leukocytes do not adhere. Washed platelets suspended in human Ringer solution exhibit negligible adhesion (at the platelet concentrations employed) in contrast to washed platelets suspended in plasma. Addition of purified human fibrinogen (95% clottable, 2-4 mg/ml) to human Ringer solution completely restores the ability of washed platelets to adhere to collagen fibers. Albumin (fatty acid free, 50 mg/ml) is also capable of restoring adhesion. Albumin and seven other proteins at concentrations of 5-10 mg/ml, with varying molecular weights, isoelectric points, and frictional coefficients are incapable of supporting the adhesion of washed platelets. The proteins tested were human globulin, hexokinase, hemoglobin, cytochrome-C, insulin, thyroglobulin, and muramidase. Platelet adhesion is proportional to both platelet concentration and fibrinogen concentration, but is independent of temperature or glycogen stores. Modification of fibrinogen by acylation of amino groups or removal of sialic acid has no effect on its ability to support platelet adhesion. Degradation of fibrinogen with purified plasmin results in decreased support of platelet adhesion. This accompanied formation of early breakdown products with clottability ranging from 84-0%. Formation of fibrinogen degradation products was monitored by SDS-polyacrylamide gel electrophoresis of the corresponding fibrins after reduction of disulfide bonds (a method capable of distinguishing alpha-, beta- and gamma-chains). Decreased support of platelet adhesion is associated with the disappearance of intact alpha- chains and early modification of the beta-chains. Purified proteinpolysaccharide macromolecules obtained from bovine nasal and humeral cartilage, and from nucleosus pulposus are as effective as fibrinogen on a weight basis and ten to thirty times more effective on a molar basis in supporting platelet adhesion. The purified mucopolysaccharide side chains: chondroitin-4-sulfate, chondroitin-6-sulfate, and keratan-sulfate are incapable of supporting platelet adhesion.
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PMID:Biochemical and biophysical aspects of human platelet adhesion to collagen fibers. 556 92

The enzyme activities and isozyme distribution of some glycolytic enzymes were studied in the K562 cell line before and after induction of hemoglobin formation. Special attention was paid to the three regulator enzymes of glycolysis, hexokinase, phosphofructokinase and pyruvate kinase. Results for the K562 cell line were compared with those for the mature red cell. K562 cells exhibit a relatively low phosphofructokinase and high pyruvate kinase activity. Electrophoresis of hexokinase shows the presence of two bands in the HK I region. HK II is also present, probably as a result of culture conditions. Only 15% of the total hexokinase activity is mitochondrial bound. Phosphofructokinase in K562 cells is mainly composed of the L- and F-types of which the F-type is characteristic for platelets and granulocytes and not for erythrocytes. In the electrophoretic pattern of pyruvate kinase a predominant K4 band besides three hybrids were found. The hybrids were demonstrated to contain L-type subunits of pyruvate kinase, which means a new erythroid marker of K562 cells, as the red cell is the only blood cell that contains L-type pyruvate kinase. Induction experiments with hemin, ARA-C and mitomycin-C gave rise to more than 85% benzidine positive cells after 11 days of culture. The isozyme composition of pyruvate kinase did not change after induction. HK II disappears after induction with ARA-C and mitomycin-C but not with hemin. The results support the idea of the multipotential features of the K562 cell line.
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PMID:Glycolytic enzymes of an erythroleukemic cell line, K562, before and after hemoglobin induction. 622 99

1-Formylpyridine monothiosemicarbazonato copper II (CuL+) is readily taken up by red cells and is initially bound to glutathione and hemoglobin. Glutathione was depleted within 5 hr of incubation, presumably by oxidation mediated by CuL+ and O2 with concomitant generation of toxic oxygen species. Cupric ion was slowly transferred from CuL+ to hemoglobin within about 7 hr and hemoglobin was oxidized until the major form prevailing after 10 hr was alpha 2 beta 2+. Little increase in hemolysis due to addition of CuL+ dissolved in the radical scavenger dimethyl sulfoxide was observed with prolonged incubation. Strong inhibition of red cell hexokinase by CuL+ was observed when the enzymes in red cell lysates and hemoglobin-free red cell lysates were examined. CuL+ was also an effective inhibitor of yeast hexokinase. However, the inhibitory effect of CuL+ within the red cells was less pronounced. It is suggested that even though intracellular accumulation of CuL+ creates an oxidizing environment and is potentially capable of inhibiting thiol enzymes such as hexokinase, protective effects are exerted in the red cell by the presence of hemoglobin, of radical scavengers, and of high levels of enzymes that detoxify toxic oxygen species.
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PMID:Effects of 2-formylpyridine monothiosemicarbazonato copper II on red cell components. 622 4

The glycolytic process in non-infected and A. marginale-infected bovine erythrocytes was studied. The study included four enzymes: hexokinase, phosphofructokinase, pyruvic kinase and lactic dehydrogenase, and the intracellular concentrations of glucose, ATP and 2,3 diphosphoglyceric acid (DPG). The activities of phosphofructokinase and lactic dehydrogenase found in non-infected bovine erythrocytes were fifty times greater than the previously reported values. Glucose and DPG concentrations, hexokinase, pyruvic kinase and lactic dehydrogenase specific activities did not change significantly during experimental anaplasmosis. Phosphofructokinase activity in A. marginale-infected erythrocytes increased to values 300% of those found in intact bovine red cells. ATP concentration in infected erythrocytes decreased to values of 40% of those found in non-infected cells: from 1.60 +/- 0.40 to 0.70 +/- 0.08 mumole per gram of hemoglobin.
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PMID:The effect of Anaplasma marginale on the glycolytic pathway in bovine erythrocytes. 623 33

Glycosylated hemoglobin and blood sugar levels in the fasting state and two hours after oral 100 g glucose load were measured in 180 patients. Glycosylated hemoglobin was measured by cation exchange column chromatography, and blood sugar was measured by hexokinase reaction. Patients with an elevated postprandial and/or fasting blood sugar level (positive screen) subsequently underwent three-hour glucose tolerance test. The mean value of glycosylated hemoglobin in patients with a negative screen and normal hemoglobin was 6.17 +/- 0.61%; and the value for glycosylated hemoglobin in patients with class A diabetes and normal hemoglobin electrophoresis was 6.85 +/- 0.73% (P less than .001). A glycosylated hemoglobin value greater than 6.78 (mean + 1 SD) was considered elevated. Glycosylated hemoglobin values were elevated in 21 of 33 patients with gestational diabetes and in 27 of 147 patients with normal blood sugar levels. The sensitivity and specificity of glycosylated hemoglobin for the diagnosis of gestational diabetes were 63.6 and 81.6%, respectively. Fifty percent of patients with an initially elevated glycosylated hemoglobin value delivered macrosomic infants, whereas no patient with a normal glycosylated hemoglobin value had a macrosomic infant. An elevated glycosylated hemoglobin value may alert the obstetrician of a potentially elevated mean blood sugar level and may warrant aggressive management of gestational diabetes.
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PMID:Use of glycosylated hemoglobin as a screen for macrosomia in gestational diabetes. 646 65


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