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)

Inhibition of glutamate transport is a potential indirect cause of excitotoxic damage by glutamate in the CNS. The mercuric ion, the form in which metallic mercury vapor is believed to exert its neurotoxic action, is a known inhibitor of amino acid transport. This study examines the specificity with which HgCl2 inhibits glutamate transport in mouse cerebral astrocytes by means of comparative measurements of 2-deoxyglucose uptake. Uptake of 2-deoxyglucose is an index of glucose utilization that reflects the function of Na+,K+-ATPase and hexokinase, and is sensitive to Na+ entry. The kinetic parameters, ionic dependence, and substrate specificity of glutamate transport in these astrocyte cultures were consistent with the commonly occurring system designated X-AG. Acute exposure to 0.5 microM HgCl2 inhibited by 50% the initial rate of glutamate transport but did not affect 2-deoxyglucose uptake. Glutamate transport was not detectably inhibited by Al2+, Pb2+, Co2+, Sr2+, Cd2+, or Zn2+ (10 microM as chlorides). The inhibitory action of 0.5 microM HgCl2 on glutamate transport was rapidly reversible. The action of 1-2 microM HgCl2 was progressive when exposures were extended to 1-3 h, and was more slowly reversible. These results suggest that Hg2+ can impair glial glutamate transport reversibly at exposure levels that do not compromise some other vital cell functions.
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PMID:Specificity and reversibility of the inhibition by HgCl2 of glutamate transport in astrocyte cultures. 289 9

Previous studies have demonstrated the presence of two type III hexokinase isozymes in pig mature erythrocytes. The prevalence of a specific isozyme species is an age-dependent phenomenon. The mature erythrocyte of young adult pigs (less than 6 mo old) possess an isozyme that has an apparent Km for glucose that is lower than in adult pigs. The data in this report suggest several basic differences between the two isozymes. D-Mannoheptulose, a structural analogue of glucose, was observed to differentially inhibit the isozymes. The young adult isozyme tended to be heat sensitive when compared with adult isozymes. Carboxypeptidase B and trypsin inhibited the activity of both isozymes, but the young adult isozyme was most dramatically affected by carboxypeptidase B. When the two isozymes were incubated in the presence of two sulfhydryl group inhibitors, HgCl2 and 5,5'-dithiobis [2-nitrobenzoic acid] (DTNB), the young adult isozyme exhibited the greater inhibition in the presence of DTNB. The data suggest that the young adult isozyme exhibited pronounced differences in activity when incubated in the presence of DTNB and carboxypeptidase B. These two agents may be used as probes to further characterize the properties of the two isozymes.
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PMID:Properties of pig mature erythrocyte hexokinase. 407 95

Highly purified adenylate translocase (ANT) from rat heart mitochondria was functionally reconstituted as ATP/ADP exchange carrier in asolectin/cardiolipin vesicles. The ANT preparations used were free of porin, cyclophilin D, and Bax as analysed immunologically and by activity measurements. After pre-loading the ANT-containing proteoliposomes with ATP, malate or AMP, a gradual release of the trapped compounds by increasing the external Ca2+ concentrations could be demonstrated. N-Methyl-Val-4-cyclosporin did not inhibit the Ca2+ dependent release of internal substances from ANT liposomes. This inhibitor was found to be specific for the mitochondrial permeability transition pore (MTP) in intact mitochondria or reconstituted MTP-like protein complexes (e.g. hexokinase, porin, ANT complex). However, ADP in concentrations > 20 microM inhibited the liberation of internal compounds, while in contrast, atractyloside (30 microM) and HgCl2 (5 microM) both induced permeability of the ANT-containing liposomes resulting in a release of trapped substances. These results strongly suggest that ANT itself is capable to adopt a pore-like structure under conditions known to induce the permeability transition in mitochondria.
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PMID:Reconstituted adenine nucleotide translocase forms a channel for small molecules comparable to the mitochondrial permeability transition pore. 959 86

Low concentrations of HgCl2 elicited, in Saccharomyces cerevisiae, a transitory increase in the ATP level followed by a decrease of its concentration, until almost disappearance. At 1 microM HgCl2, the increase in ATP lasted for about 30 min, while at 10 microM the increase was only observed in the first 5 min of treatment. The initial burst of ATP was accompanied by a decrease in the level of hexose phosphates, whereas during the decrease of ATP an increase in the inosine and hexose phosphates levels took place. The treatment with HgCl2 inhibited the plasma membrane proton ATPase but not the activities of hexokinase or 6-phosphofructokinase.
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PMID:Micromolar HgCl2 concentrations transitorily duplicate the ATP level in Saccharomyces cerevisiae cells. 1602 9