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 stability of various glycolytic enzymes of human erythrocytes has been studied by the mechanical shaking method. The rate of denaturation apparently followed first order kinetics. The t1/2, the shaking time required to denature 50% of the original activity, for glucose-6-phosphate dehydrogenase, phosphofructokinase, and pyruvate kinase was less than 1 min; that for hexokinase, 6-phosphogluconate dehydrogenase, and monophosphoglyceromutase was between 2 and 13 min; that for all the other enzymes was more than 30 min. Since the t1/2 value for each enzyme is highly reproducible if the shaking conditions are kept constant, these parameters may be used as an indicator of protein stability in solution. The mechanical denaturation method may also be used to remove unstable components from a mixture of proteins with different stabilities.
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PMID:Stability of glycolytic enzymes of human erythrocytes. 83 47

The limited deformability and ATP depletion was considered by some authors to be the factor limiting the life span of old red blood cells (RBC) in circulation. Others believed that sialic acid on the RBC surface determines their life span. We compared the life span of 51Cr labelled, neuraminidase treated rabbit RBCs with ATP depleted by incubation at 37 degree C rabbit RBCs. Osmotic fragility, agglutinability, glucose-6-phosphate dehydrogenase (G6PD) and hexokinase activity and ATP levels of these cells were determined. Desyalated RBCs were removed from the circulation within 24 hours. ATP levels, G6d and hexokinase activity and osmotic fragility were normal in these cells. The agglutination by poly(L-lysine) was affected by the loss of surface charge on these cells. Half the ATP depleted RBCs were out of the circulation within three days. Reconstitution of ATP by reincubation with adenosine, elevated the ATP levels to about 80% of their original level, but survival of these cells did not improve. Analysis of sialic acid showed tha 50% of it was removed during the incubation for ATP depletion. The low ATP level and loss of sialic acid fromt he RBC membrane appeared to be conincidental rather than dependent on each other. The latter appears to be a primary factor in red cell survival.
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PMID:Rabbit erythrocyte survival following diminished sialic acid and ATP depletion. 86 45

We have adapted the hexokinase glucose procedure to an immobilized enzyme stirrer for the determination of glucose concentrations in human blood plasma. The procedure is a fluorometric rate method measuring the formation of NADPH catalyzed by immobilized glucose-6-phosphate dehydrogenase and hexokinase held within a tiny stirrer. The enzyme stirrer is stable for at least two months and can be used over eight-hundred assays without any loss of activity.
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PMID:An immobilized hexokinase enzyme stirrer for a simple and economical assay of plasma glucose. 88 73

The authors investigated the in vitro functional differentiation of fetal mouse liver cultured in Rose's circumfusion system with the use of two biochemical markers: The analysis of the inductive response of key enzymes in carbohydrate metabolism to insulin, and the analysis of the liver-specific isozyme of pyruvate kinase [EC 2.7.1.40]. The glucokinase [EC 2.7.1.2] activity, which is only found in mammalian adult liver, emerged on cultivation of 2-3 days and reached a maximum level equivalent to one-half of the adult level. Two- or 3-fold increases in the glucokinase, pyruvate kinase, and glucose-6-phosphate dehydrogenase [EC 1.1.1.49] were induced by a single dose of insulin in fetal liver after 12 days of cultivaton. Hexokinase [EC 2.7.1.1] activity was barely influenced by insulin. These results suggested that fetal mouse liver cultured in this system for 2 weeks maintained the same response to insulin as in vivo adult mouse liver. The pyruvate kinase isozyme patterns of mouse livers in various developmental stages and of cultured fetal mouse liver in the present system were investigated by isoelectric fractionation. The pyruvate kinase isozymes having the highest relative activity were the pI-5.5 isozyme for the adult liver and the pI-6.5 isozyme for 13- to 14-day-old fetal liver. As development in vivo proceeded, a gradual change in isozyme pattern occurred; this consisted of a progressive decrease of the pI-6.5 pyruvate kinase isozyme, "fetal type," in favor of the pI-5.5 isozyme, "adult type." The pyruvate kinase isozyme pattern in 13- to 14-day fetal liver cultured in the system for 2 weeks was similar to that found in adult liver. Thus, it was shown that "fetal type" pyruvate kinase was also replaced by "adult type" pyruvate kinase in vitro. It can be concluded from these findings that fetal mouseliver cultured in the circumfusion system for 2 weeks maintains its functional and morphological identitites as it differentiates toward the adult liver.
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PMID:Functional differentiation of mouse fetal liver in circumfusion system cultures. 93 74

The activities of glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate: NADP oxidoreductase, G6PD), 6-phosphogluconate dehydrogenase (6-phospho-d-gluconate: NADP oxidoreductase, 6PGD), hexokinase (ATP:D-hexose 6-phosphotransferase, HK), lactic dehydrogeanse (L-lactate: NAD oxidoreductase, LDH) and aspirate aminotransferase (L-aspartate: 2-oxoglutarate aminotransferase, Asp.T) were determined in red blood cells of 11 healthy individuals. The determinations were carried out on samples drawn every 4 h over a 24 h period. The activities of G6PD, 6PGD, LDH and Asp.T exhibited a semi-circadian rhythm, namely, two peaks of activity during 24 h while HK activity demonstrated a true circadian rhythm. In addition a polymorphism of the G6PD and LDH activity patterns was observed. The implications of a biological clock in enucleated cells are discussed.
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PMID:The diurnal rhythm of enzymes in human red cells. 94 47

A novel flow-enthalpimetric analyzer is described and its use demonstrated by an analysis in which glucose is determined by its hexokinase-catalyzed phosphorylation reaction. The method depends on measurement of the temperature differential across a column packed with glass-supported immoblized enzyme. Sample volumes of 120 mul can be used to obtain a calibration curve that is linear up to 25 mmol of glucose per liter. A precision (within-day) of 5% is generally observed in the optimum concentration range where glucose is quantitatively phosphorylated. Results by the technique correlate reasonably with those by the o-toluidine and the hexokinase/glucose-6-phosphate dehydrogenase methods: Other sugars--including fructose, glucosamine, and mannose--will interfere; galactose does not. The technique is amenable to both routine and emergency analyses.
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PMID:An immobilized-enzyme flow-enthalpimetric analyzer: application to glucose determination by direct phosphorylation catalyzed by hexokinase. 95 91

Ireport a detailed series of microcalorimetric measurement of glucose concentrations in five reference samples of serum. The method utilized (a) calibration in the actual medium of analysis and (b) a correction for interferences owing to the nonspecificity of the enzyme hexokinase. The microcalorimetric results are compared with the tentative results of analyses obtained by the spectrophotometric hexokinase/glucose-6-phosphate dehydrogenase method and by isotope-dilution mass spectrometry. In most cases, the microcalorimetric results appear to be in agreement with the results obtained by these latter two methods. A discussion of the basis of the microcalorimetric measurements is presented.
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PMID:Microcalorimetric determination of glucose in reference samples of serum. 97

Acetaminophen, p-aminophenol, and oxyphenbutazone interfere with the glucose oxidase/peroxidase method for glucose. Structurally related compounds that lack a free phenolic hydroxyl group (acetanilide, aniline, and phenylbutazone) do not interfere. During the analytical procedure acetaminophen is consumed. One mole of acetaminophen leads to an apparent loss of four moles of glucose. The hexokinase/glucose-6-phosphate dehydrogenase method (Boehringer Hexokinase method) is not affected by these substances.
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PMID:Interference by acetaminophen in the glucose oxidase-peroxidase method for blood glucose determination. 97 21

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


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