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)

1. Carbohydrate metabolism was studied in HT29 human colon cancer cells cultured in a glucose free medium supplemented with 2.8 mM inosine (HT29ino cells) in comparison with standard HT29 cells grown in the permanent presence of glucose (HT29Glc + cells) and with HT29Glc- cells which are adapted to grow permanently without glucose. 2. Inosine allows the standard cells to grow when glucose is lacking but surprisingly stops the growth of HT29Glc- cells. 3-mercaptopicolinate, an inhibitor of PEP-carboxykinase, does not hinder HT29ino cells to grow, which shows that gluconeogenesis from aspartate or pyruvate is not essential. It suggests that enough carbohydrate is supplied by the ribose moiety of inosine. 3. While standard HT29Glc + cells are highly glycolytic, it is not the case of HT29ino or HT29Glc- cells when glucose is given for few hours. When glucose is present for 24 hr or more, glycolytic rate increases in HT29ino cells and glycogen accumulates. 4. It is found that the pattern of enzymes activities related to carbohydrate metabolism in HT29ino cells is closer to that of HT29Glc + cells rather than to that of HT29Glc- cells. However, phosphofructokinase-1 activity, measured with saturating concentration of Fru-2,6-diP, is significantly lower in HT29ino cells. 5. Binding rate of hexokinase to mitochondria is similar in the three cell-lines. However, in HT29Glc- cells, bound hexokinase easily utilizes ATP generated by the mitochondria. By contrast, in HT29Glc+ and HT29ino cells, bound hexokinase is much more active with exogenous ATP, suggesting a functional defect in the mitochondria from these two latter cells.
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PMID:Carbohydrate metabolism in HT29 colon cancer cells cultured in a glucose free medium supplemented with inosine. 252 33

The regulatory properties of pig erythrocyte hexokinase III have been studied. Among mammalian erythrocyte hexokinases, the pig enzyme shows the highest affinity for glucose and a positive cooperative effect with nH = 1.5 at all the MgATP concentrations studied (for 0.5 to 5 mM). Glucose at high concentrations is also an inhibitor of hexokinase III. Similarly, the apparent affinity constant for MgATP is independent of glucose concentration. Uncomplexed ATP and Mg are both competitive inhibitors with respect to MgATP. Glucose 6-phosphate, known as a stronger inhibitor of all mammalian erythrocyte hexokinases, is a poor inhibitor for the pig enzyme (Ki = 120 microM). Furthermore, this inhibition is not relieved by orthophosphate as with other mammalian red blood cell hexokinases. A variety of red blood cell-phosphorylated compounds were tested and found to be inhibitors of pig hexokinase III. Of these, glucose 1,6-diphosphate and 2,3-diphosphoglycerate displayed inhibition constants in the range of their intracellular concentrations. In an attempt to investigate the role of hexokinase type III in pig erythrocytes some metabolic properties of this cell have been studied. The adult pig erythrocyte is able to utilize 0.27 mumol of glucose/h/ml red blood cells (RBC) compared with values of 0.56-2.85 mumol/h/ml RBC for the other mammalian species. This reduced capacity to metabolize glucose results from a relatively poor ability of the cell membrane to transport glucose. In fact, all the glycolytic enzymes were present and a low intracellular glucose concentration was measured (0.5 mM against a plasma level of 5 mM). Furthermore, transport and utilization were concentration-dependent processes. Inosine, proposed as the major energy substrate of the pig erythrocyte, at physiological concentrations is not as efficient as glucose in maintaining reduced glutathione levels under oxidative stress. Furthermore, newborn pig erythrocytes (fully permeable to glucose) possess hexokinase type II as the predominant glucose-phosphorylating activity. This fact and the information derived from the study of the regulatory characteristics of hexokinase III and from metabolic studies on intact pig erythrocytes permit the hypothesis that the presence of this peculiar hexokinase isozyme (type III) enables the adult pig erythrocyte to metabolize low but appreciable amounts of glucose.
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PMID:Pig red blood cell hexokinase: regulatory characteristics and possible physiological role. 660 23