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)

Analyses of key glycolytic intermediates in freshly drawn red cells from six related individuals suggest that decreased hexokinase activity underlies the hemolytic process in the two members with overt hemolysis. Low red cell glucose 6-phosphate (G6P) was observed not only in the anemic patients but in the presumptive heterozygotes as well and served as a useful marker for the presence of the trait. Hexokinase activity was labile in distilled water hemolysates but was only slightly low when protected by glucose, mercaptoethanol, and ethylenediaminetetraacetate (EDTA). Normal red cell hexokinase was demonstrated to be dependent on glucose for maintenance of activity after heating to 45 degrees C. The cells of the proposita are unable to utilize glucose efficiently at glucose concentrations lower than 0.2 mmole/liter whereas normal cells maintain linear glucose consumption to at least 0.05 mM glucose. These qualitative abnormalities could result from the presence of a mutant hexokinase with an abnormally reactive sulfhydryl group and altered substrate affinity in the red cells of this kindred.
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PMID:Hemolytic anemia with impaired hexokinase activity. 498 Sep 29

1. The submitochondrial localization of hexokinase activity in preparations of mitochondria from the small intestine of the guinea pig was studied by conventional methods. 2. Hexokinase activity in this tissue was predominantly associated with the outer mitochondrial membrane. 3. The inactivation of mitochondrial enzymes by trypsin in iso-osmotic and hypo-osmotic conditions was also used to determine the submitochondrial localization of hexokinase activity. 4. Hexokinase activity was found to be on the outside of the outer mitochondrial membrane. 5. It was shown that both type I and type II hexokinase activities are bound to the outside of the outer mitochondrial membrane. The types are present in the same ratio as that in which they occur in the cytosol of the cell. 6. Mitochondrial hexokinase from the small intestine did not show the latency phenomenon demonstrated by mitochondrial hexokinase from brain when subjected to a variety of treatments. However, hexokinase activity was solubilized from preparations of mitochondria from the small intestine by the same treatments as for mitochondrial hexokinase from brain. 7. The submitochondrial distribution of hexokinase activity in mitochondrial preparations from rat brain was determined by the trypsin inactivation method. 8. Hexokinase activity in preparations of mitochondria from rat brain was found on the outside of the outer membrane, between the mitochondrial membranes, and within the inner mitochondrial membrane. 9. Hexokinase from rat brain showed latency properties irrespective of its submitochondrial location.
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PMID:Mitochondrial hexokinase from small-intestinal mucosa and brain. 513 35

1. The effect of three dietary components on hexokinase activity in the mucosa of rat small intestine was studied in vivo. Glucose, amino acids or an emulsion of monoglyceride with long-chain fatty acids were given by stomach tube to previously starved rats, and hexokinase activity was determined in the particle-free supernatant of mucosal homogenates. The formation of lactate from glucose and glucose 6-phosphate respectively was also measured. 2. When the three dietary components were given in isocaloric amounts, only glucose brought about an increase in hexokinase activity. 3. Intravenous injection of a similar amount of glucose to that given orally did not alter hexokinase activity. 4. An increase in the hexokinase activity of the particle-free supernatant prepared from mucosal homogenates was also observed after sacs of the small intestine of starved rats had been incubated in vitro in a medium containing glucose. Hexokinase activity increased to the values observed in corresponding preparations from fed rats, and this increase was strictly glucose-dependent.
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PMID:Glucose metabolism in the mucosa of the small intestine. The effect of glucose on hexokinase activity. 577 50

1. Measurements were made of the non-oxidative reactions of the pentose phosphate cycle in liver (transketolase, transaldolase, ribulose 5-phosphate epimerase and ribose 5-phosphate isomerase activities) in a variety of hormonal and nutritional conditions. In addition, glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase activities were measured for comparison with the oxidative reactions of the cycle; hexokinase, glucokinase and phosphoglucose isomerase activities were also included. Starvation for 2 days caused significant lowering of activity of all the enzymes of the pentose phosphate cycle based on activity in the whole liver. Re-feeding with a high-carbohydrate diet restored all the enzyme activities to the range of the control values with the exception of that of glucose 6-phosphate dehydrogenase, which showed the well-known ;overshoot' effect. Re-feeding with a high-fat diet also restored the activities of all the enzymes of the pentose phosphate cycle and of hexokinase; glucokinase activity alone remained unchanged. Expressed as units/g. of liver or units/mg. of protein hexokinase, glucose 6-phosphate dehydrogenase, transketolase and pentose phosphate isomerase activities were unchanged by starvation; both 6-phosphogluconate dehydrogenase and ribulose 5-phosphate epimerase activities decreased faster than the liver weight or protein content. 2. Alloxan-diabetes resulted in a decrease of approx. 30-40% in the activities of 6-phosphogluconate dehydrogenase, ribose 5-phosphate isomerase, ribulose 5-phosphate epimerase and transketolase; in contrast with this glucose 6-phosphate dehydrogenase, transaldolase and phosphoglucose isomerase activities were unchanged. Treatment of alloxan-diabetic rats with protamine-zinc-insulin for 3 days caused a very marked increase to above normal levels of activity in all the enzymes of the pentose phosphate pathway except ribulose 5-phosphate epimerase, which was restored to the control value. Hexokinase activity was also raised by this treatment. After 7 days treatment of alloxan-diabetic rats with protamine-zinc-insulin the enzyme activities returned towards the control values. 3. In adrenalectomized rats the two most important changes were the rise in hexokinase activity and the fall in transketolase activity; in addition, ribulose 5-phosphate epimerase activity was also decreased. These effects were reversed by cortisone treatment. In addition, in cortisone-treated adrenalectomized rats glucokinase activity was significantly lower than the control value. 4. In thyroidectomized rats both ribose 5-phosphate isomerase and transketolase activities were decreased; in contrast with this transaldolase activity did not change significantly. Hypophysectomy caused a 50% fall in transketolase activity that was partially reversed by treatment with thyroxine and almost fully reversed by treatment with growth hormone for 8 days. 5. The results are discussed in relation to the hormonal control of the non-oxidative reactions of the pentose phosphate cycle, the marked changes in transketolase activity being particularly outstanding.
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PMID:The pentose phosphate pathway of glucose metabolism. Hormonal and dietary control of the oxidative and non-oxidative reactions of the cycle in liver. 579 34

1. Extractable hexokinase activity was measured in the red and white skeletal muscles of the rabbit and in the hearts and diaphragms of four animal species differing markedly in size. Activities vary over a 40-fold range, being least in white skeletal muscle of the laboratory rabbit and greatest in mouse heart. 2. Hexokinase activities correlate approximately with capacities to undertake reactions of the tricarboxylic acid cycle as determined by succinate oxidase assays. Both enzyme activities seem best related to the average contractile-energy expenditure per unit weight of muscle over an extended period, rather than to the rapidity of individual contractions. 3. Hexokinase and succinate oxidase activities cannot be related to a muscle's content of soluble pigment. They display an inverse relationship with activities of phosphorylase and glycolytic enzymes, but only within the group of rabbit skeletal muscles whose oxidative capacities are at the lower end of the observed range. 4. Total glycogen-UDP glucosyltransferase activities do not vary significantly between rabbit skeletal muscles, although those of hexokinase differ by about sixfold. On the average, glucose 6-phosphate is probably oxidized directly. However, observations cited in the literature suggest that muscles with an active hexokinase may well preferentially accumulate glycogen when glucose is present in excess of the fibres' capacity to oxidize it. 5. When considered with published results obtained in vivo, the present findings indicate that phosphorylase has a minor role in the energy expenditure of muscles with a predominantly oxidative metabolism. In these, the major substrates appear to be blood glucose, fatty acids and possibly lipids. 6. The histochemical criteria by which muscle fibres are commonly described as red or white are inadequate.
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PMID:The activities of some enzymes concerned with energy metabolism in mammalian muscles of differing pigmentation. 580 88

1. Measurements were made of the activities of enzymes of the pentose phosphate cycle, glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, ribose 5-phosphate isomerase, ribulose 5-phosphate epimerase, transketolase and transaldolase, as well as of the related or competing enzymes glucokinase, hexokinase, phosphoglucose isomerase and phosphoglucomutase, in control rats and in rats bearing the growth-hormone- and prolactin-secreting pituitary tumour MtTW5, to study the effect of high endogenous concentrations of growth hormone on this pathway in liver. 2. There was a twofold increase in liver weight. Glucokinase activity/g. of liver decreased to half the control value in the experimental group, although on a total liver basis it remained unchanged. Hexokinase activity increased in parallel with the liver weight, so that the total activity was doubled in rats with a high endogenous concentration of growth hormone. No differences in response were found between heat-stable and heat-labile forms of hexokinase. 3. The activity/g. of liver of the two oxidative enzymes of the pathway decreased slightly in the experimental group, but this was offset by the increase in liver weight, and the resultant effect was a 50% increase in the total activity. 4. Of the non-oxidative enzymes of the cycle the most marked increase on a total liver basis was in ribose 5-phosphate isomerase activity, to 2.5 times the control value. Ribulose 5-phosphate epimerase activity showed the smallest increase. Transketolase and transaldolase activities were also increased. The latter is the rate-limiting enzyme of the non-oxidative reactions of the cycle in these animals. 5. The results are discussed in relation to the glycolytic pathway and synthesis of glycogen, and more particularly to the increased requirement for ribose 5-phosphate for RNA synthesis.
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PMID:The pentose phosphate pathway of glucose metabolism. Influence of a growth-hormone-secreting pituitary tumour on the oxidative and non-oxidative reactions of the cycle in liver. 580 93

1. Glucokinase and hexokinase activities have been determined in the livers of newborn rats and attempts made to influence in vivo the development of the glucokinase. 2. Glucokinase first appears in rat liver about 16 days after birth and adult activities are reached 10-12 days later. Evidence is presented which indicates that this represents synthesis of new protein. Hexokinase activities remain constant throughout the period of glucokinase development. 3. Both exogenous glucose and insulin are necessary for the natural development of glucokinase, for this is retarded in starved and alloxan-diabetic neonatal rats. 4. The absence of glucokinase during the first 2 weeks of extrauterine life in the rat is not due to lack of insulin. 5. Attempts to advance the time at which glucokinase first appears by infusions of glucose, insulin and chlorpropamide alone and in various combinations have resulted in marginal effects only. 6. When rats are starved for 3 days during the period of glucokinase development and then re-fed, glucokinase is more rapidly synthesized, indicating that the potential ability to synthesize glucokinase continues to develop throughout the period of starvation. 7. Some possible reasons for the comparatively late development of glucokinase are discussed.
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PMID:The development of hepatic glucokinase in the neonatal rat. 588 29

Hexokinase activity in human erythrocytes is associated with three electrophoretically distinct bands. Normal adult erythrocytes contain hexokinases Types I and III. Type II hexokinase is present in the erythrocytes of newborn infants and absent from those of normal adults; it is, however, present in erythrocytes of adults with hereditary persistence of fetal hemoglobin. Type II hexokinase and fetal hemtoglobin appear to be associated.
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PMID:Hexokinase isoenzymes in human erythrocytes: association of type II with fetal hemoglobin. 602 56

The freshwater murrel, Channa punctatus, was exposed to a sublethal concentration of mercuric chloride (3 micrograms/liter) for 120 days and the following effects were examined: changes in the levels of glucose and lactic acid in blood and of glycogen and lactic acid in liver and muscles; rate of absorption of glucose from the intestine; and changes in the activities of glucose-6-phosphatase (G-6-Pase), hexokinase, lactate dehydrogenase (LDH), pyruvate dehydrogenase (PDH), succinate dehydrogenase (SDH), malate dehydrogenase (MDH), glutamate dehydrogenase (GDH), L-amino acid oxidase (AO), and xanthine oxidase (XO) in brain, gills, intestine, kidney, liver, and muscles. Mercury-treated fish were hypoglycemic and hypolactemic. The glycogen content of liver and muscles remained unaltered but the muscle lactic acid level decreased significantly. The rate of intestinal absorption of glucose was reduced significantly by exposure to mercury. G-6-Pase activity was decreased in all the tissues. Hexokinase activity also decreased in mercury-exposed fish but it was significant only in intestine, kidney, and liver. The activities of LDH, PDH, SDH, and MDH also were decreased significantly except LDH in brain and MDH in kidney where an insignificant decrease and an insignificant increase, respectively, were recorded. GDH and AO activities were elevated in most of the tissues except GDH in gills, and AO in gills and muscles where a decrease was observed. XO activity in brain, gills, and kidneys was significantly elevated, but no marked alteration was noted in other tissues.
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PMID:Effect of mercuric chloride on some biochemical and physiological parameters of the freshwater murrel, Channa punctatus. 608 7

Key enzyme activities of carbohydrate metabolism were evaluated as sensitive indicators of liver cell injury of rats. Hexokinase and glucose 6-phosphatase distribution in the acinus of the liver was also studied histochemically with the following results: The activities of liver-specific enzymes, such as glucose 6-phosphatase, fructose 1.6-diphosphatase, glucokinase and pyruvate kinase Type L, were decreased. While the activities of nonspecific enzymes to liver, such as hexokinase, glucose 6 phosphate dehydrogenase, phosphofructokinase and pyruvate kinase Type M2 were increased. The decrease in glucokinase activity was marked and was found as early as one day after bile duct ligation. Isozymes of HK, I, II and III, all increased to the same extents. Increased hexokinase activity was found in the centrolobular area, where the decreased activity of glucose 6-phosphatase was observed. These changes in the key enzyme activities indicated the presence of a hepatocyte injury caused by bile duct ligation.
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PMID:[Studies on liver cell injury in obstructive jaundice: activities of key enzymes responsible for carbohydrate metabolism in rat after bile duct ligation]. 608 12


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