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)

The respiration of rabbit heart mitochondria in the presence of ATP is stimulated by ADP, AMP, creatine and glucose plus hexokinase. The values of V for mitochondrial phosphorylating respiration in the presence of corresponding stimulators are equal to 491 +/- 34, 460 +/- 12, 480 +/- 45 and 463 +/- 72 natoms O2 X min-1 X mg-1 of protein, 37 degrees C. The half-maximal stimulation of respiration is observed at 35 microM AMP, 60 microM ADP and 10 mM creatine in the absence of creatine phosphate. In the presence of creatine phosphate the maximal stimulation of heart mitochondrial respiration is achieved under a combined action of creatine and AMP. The inhibition type of mitochondrial respiration by palmitoyl-CoA depends on the nature of stimulators used. Thus, with ADP or glucose plus hexokinase the inhibition is competitive, while with AMP and creatine an uncompetitive and non-competitive inhibition was observed, respectively. The experimental results are indicative of functional coupling of heart mitochondrial adenylate kinase and creatine phosphokinase with ATP-ADP-translocase. It is assumed that creatine and AMP act as physiological regulators of heart mitochondrial respiration ("feed-back" signals from cytoplasm to mitochondria).
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PMID:[Functional coupling of creatine phosphokinase and adenylate kinase with adenine nucleotide translocase and its role in regulation of heart mitochondrial respiration]. 631 78

The 2-azidoadenine nucleotides show promise as photoaffinity probes. Substitution at the C-2 position should favor an anti conformation and enable binding of the analogue to enzyme sites which exhibit low affinity for the 8-azidoadenine derivatives. The 2-azidoadenine nucleotides were found to be substrates for pyruvate kinase, phosphofructokinase, adenylate kinase, hexokinase and the mitochondrial F1-ATPase. However, tautomerism of 2-azidoadenine nucleotides to two nonphotoreactive tetrazole forms complicates kinetic analyses and their use as photoaffinity probes. An analysis of the ultraviolet spectra of these analogues enables an estimation of the tetrazolo isomer content and the rates of tautomerization. The photoreactive azido isomer was found to represent only 45% of the total analogue population in neutral aqueous solution. The azidoazomethine-tetrazole equilibrium favors the azido isomer in acidic or nonpolar solutions. The first-order rate constants at 25 degrees C were determined to be 0.017 min-1 and 0.021 min-1 for tautomerism to the azido and tetrazolo isomers, respectively. Prior equilibration of the probe in various solvents thus allows investigation of the analogue's behavior with an enzyme system at different, essentially fixed, isomer ratios. The determination of the impact of the tetrazolo tautomers on the system allows optimization of conditions for photoaffinity-labeling experiments.
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PMID:Tautomerism of 2-azidoadenine nucleotides. Effects on enzyme kinetics and photoaffinity labeling. 633 19

Evidence is presented for the occurrence of glycosomes (organelles resembling peroxisomes) in four major species of Leishmania (viz. L. major, L.m. mexicana, L. b. braziliensis and L. donovani), based on latency as well as differential and isopycnic centrifugation studies. The enzymes involved in glycolysis; (hexokinase, phosphoglucose isomerase, phosphofructokinase, fructose-1,6-bisphosphate aldolase, triosephosphate isomerase, glyceraldehyde-phosphate dehydrogenase and phosphoglycerate kinase); glycerol metabolism (sn-glycerol-3-phosphate dehydrogenase and glycerol kinase); carbon dioxide fixation (phosphoenolpyruvate carboxykinase and possibly malate dehydrogenase); together with an enzyme involved in the beta-oxidation of fatty acids (3-beta-hydroxybutyryl coenzyme A dehydrogenase); a key enzyme in the synthesis of ether lipids (dihydroxyacetone phosphate acyltransferase) as well as the ADP utilising enzyme adenylate kinase, were all found associated, at least in part, with a subcellular organelle which had a buoyant density in sucrose gradients of 1.21 to 1.24 g cm-3. Little variance in enzyme composition was found between the different species of Leishmania or in comparison with other members of the Trypanosomatidae, supporting the unifying principle that glycosomes are a unique characteristic of this family. The occurrence of important catabolic, anabolic and anaplerotic pathways in the glycosomes of Leishmania renders them prime targets for chemotherapy.
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PMID:The occurrence of glycosomes (microbodies) in the promastigote stage of four major Leishmania species. 644 18

The isozyme patterns and activities of six enzymes were determined in surgical biopsy samples of lung tumors and non-neoplastic pulmonary areas. Fetal lungs were also examined. No tissue differences were found in the isozyme pattern of hexokinase or alkaline phosphatase; small differences in pyruvate kinase isozyme proportions were observed. The tumors exhibited significant deviations with respect to the lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) isozyme patterns. Despite the diversity of cell types, the proportions of the M-subunit of LDH in each tumor and that of the mitochondrial isozyme of MDH in all but one tumor were higher than in control samples from the same lung. In contrast, the normal fetal lung showed a higher LDH-H proportion than did adult lung and a mature MDH isozyme pattern. The alpha-glycerophosphate dehydrogenase and adenylate kinase activities of the tumors were about one-tenth and one-fourth, respectively, of those of nonneoplastic adult lung. These lower activities (evident also in normal fetal lung) were accompanied by 3- to 5-fold increases in the LDH, MDH, pyruvate kinase, and hexokinase activities of the tumors; fetal lungs had lesser increases (2- to 3-fold) for the first 3 enzymes. The common features of tumors with different cell types and histological grade identified here point to several enzymes the quantitation or isozyme analysis of which may be of practical use in distinguishing cancerous from nonneoplastic human lung samples. A combination of different indicators, such as opposite changes in LDH and alpha-glycerophosphate dehydrogenase activity, coupled with elevated proportions of LDH-M, may be used to diagnose neoplasia most reliably.
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PMID:Enzyme activities and isozyme patterns in human lung tumors. 669 92

The role of mitochondrial hexokinase (EC 2.7.1.1.) and mitochondrial ATP synthesis in the utilization of glucose for the support of estrogen biosynthesis was examined in placental mitochondrial preparations supplemented with NADP+, glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and 4-androstene-3,17-dione. With 14 mitochondrial preparations, rates of steroid aromatization supported by 100 mM glucose and 20 mM ATP had a mean of 65.7 +/- 7.1 (SD) % of rates achieved with saturating levels of glucose 6-phosphate. ADP, but not AMP, could substitute for ATP in this system. Aromatization supported by glucose and high concentrations of ADP was inhibited by AMP but not by 2,4-dinitrophenol or oligomycin. Glucose also supported mitochondrial aromatization when combined with a respiratory chain-linked metabolic substrate (glycerol 3-phosphate) and a limiting concentration of ADP (2 mM). This support was inhibited by 2,4-dinitrophenol, the p-trifluoromethoxyphenylhydrazone of carbonyl cyanide, oligomycin and atractyloside. Thus, glucose metabolism by mitochondrial hexokinase, utilizing ATP generated either by oxidative phosphorylation or mitochondrial adenylate kinase (EC 2.7.4.3), can be coupled with a soluble NADPH-generating system to provide effective support of mitochondrial estrogen synthesis.
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PMID:The support of steroid aromatization by mitochondrial metabolic activities of the human placenta. 670 59

AMP is converted to ATP by incubating overnight with pyruvate kinase, phosphoenolpyruvate and adenylate kinase in the presence of endogenous ATP (ADP) as primer. In a subsequent incubation in the presence of pyruvate kinase, phosphoenolpyruvate, radioactive glucose and hexokinase, ATP and ADP are estimated together by coupling their recycling to the formation of glucose 6-phosphate. The latter is separated by precipitation using 76% (v/v) acetone for radioactivity measurement in the same Eppendorf tube. The sensitivity of these simple procedures matches or exceeds those of luciferase methods of nucleotide determination.
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PMID:Radioisotopic assay of femtomole quantities of total adenine nucleotides, ATP plus ADP, and AMP. 673 60

Highly purified glycosomes were isolated from Trypanosoma brucei bloodstream forms and cultured procyclic trypomastigotes. A comparison of the specific activities of glycosomal enzymes revealed that glycosomes from insect stages had decreased levels of hexokinase, phosphoglucose isomerase, phospho-fructokinase, fructose-bisphosphate aldolase, glyceraldehyde-phosphate dehydrogenase and phosphoglycerate kinase, but contained increased levels of adenylate kinase, malate dehydrogenase and phosphoenolpyruvate carboxykinase. Glycosomes from bloodstream forms were almost totally devoid of the latter two activities. Comparison of the two types of glycosomes by sodium dodecylsulphate-polyacrylamide gel electrophoresis revealed that bloodstream form glycosomes contained 3 prominent polypeptides (64, 46 and 40 kDa) which were hardly detectable in insect stage glycosomes, whereas the latter contained 3 insect stage specific bands with molecular weight of 34 000, 61 000 and 77 000 and 4 additional bands with molecular weights between 94 000 and 110 000. Both types of glycosome contained the phospholipids phosphatidylcholine and phosphatidylethanolamine. Insect stage glycosomes contained in addition also phosphatidylinositol and some phosphatidylserine.
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PMID:A comparison of the glycosomes (microbodies) isolated from Trypanosoma brucei bloodstream form and cultured procyclic trypomastigotes. 674 87

Procyclic culture forms of Trypanosoma brucei stock 427 have been screened for the presence of enzymes involved in glycolysis, mitochondrial energy metabolism and threonine degradation. The enzyme activities in the procyclics were compared with those of the blood stream forms. The specific activities of glycolytic enzymes represented 30-70% of the respective levels in the blood stream form, except for hexokinase which was 25-fold reduced. Cell fractionation showed that the enzymes involved in the early sequence of the glycolytic pathway, i.e. from hexokinase to phosphoglycerate kinase, and the enzymes NAD+-linked glycerol-3-phosphate dehydrogenase and glycerol kinase were all present in glycosomes equilibrating at a density of 1.23 g/cm3 in sucrose gradients. Malate dehydrogenase was 8-fold more active in procyclics than in bloodstream forms. This increase in activity was the result of the appearance of malate dehydrogenase in the glycosomes of the procyclics, in addition to mitochondrial and cell-sap activities which were present in both stages of the life cycle. Glycosomes contained part of the adenylate kinase activity, which was also associated with the mitochondrion. Succinate dehydrogenase and sn-glycerol-3-phosphate dehydrogenase, together with oligomycin-sensitive ATPase, were located in the mitochondrion which had a density in sucrose ranging from 1.16 to 1.18 g/cm3. This organelle also contained L-threonine 3-dehydrogenase and carnitine acetyltransferase, two enzymes involved in threonine catabolism. The latter two enzymes had activities which were, respectively, 15-and 13-fold higher in the procyclics than in the bloodstream form. Mitochondrial sn-glycerol-3-phosphate dehydrogenase was decreased 4-fold.
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PMID:Localization of malate dehydrogenase, adenylate kinase and glycolytic enzymes in glycosomes and the threonine pathway in the mitochondrion of cultured procyclic trypomastigotes of Trypanosoma brucei. 680 9

Muscle biopsies were obtained from three cyclists and four runners at the end of 10-24 mo of intensive training and after intervals of detraining up to 12 wk. Control samples came from four untrained persons and four former athletes. Macro mixed fiber samples were assayed for lactate dehydrogenase, adenylate kinase, glycogen phosphorylase, citrate synthase, malate dehydrogenase, beta-hydroxyacyl-CoA dehydrogenase, succinate dehydrogenase, beta-hydroxybutyrate dehydrogenase, creatine kinase, hexokinase, 1-phosphofructokinase, fructosebisphosphatase, protein, and total creatine. In the case of three trained persons and two controls, the first six of the enzymes were also measured in individual fibers. Before detraining, enzymes of oxidative metabolism were substantially higher than in controls, and differences in levels between type I and type II fibers were smaller. During detraining, oxidative enzymes were decreased in both fiber types but the type II fibers did not fall to control levels even after 12 wk. Phosphorylase increased with detraining in both fiber types. The same is true for lactate dehydrogenase and adenylate kinase, except in the case of the type I fibers of one individual. Among the other six enzymes (measured in mixed fiber samples), only hexokinase was consistently affected (decreased) by detraining.
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PMID:Effects of detraining on enzymes of energy metabolism in individual human muscle fibers. 682 50

Reconstituted human red blood cell ghosts have been used to assay various metabolic intermediates for their role in driving the Na:K pump. ATP was identified as the primary substrate of the pump. The main evidence was based on 1) the finding that the only requirement for activation of the pump was the presence of ATP, whether incorporated directly or generated by an ATP-yielding reaction; 2) the discriminating effects of various metabolic inhibitors; 3) the competition between the pump and hexokinase reaction for ATP; and 4) the difference in effects of adenosine and inosine in activating the pump in energy-depleted ghosts. ADP was found to affect the Na:K pump due to the presence of an adenylate kinase and perhaps because of an effect on the phosphoryl potential. The sidedness of action of the cardiotonic steroid, strophanthidin, was evaluated and found to inhibit the Na:K pump only from the outside of the membrane. Inhibition of the pump by strophanthidin was also found to spare ATP in reconstituted ghosts provided the nonspecific phosphatase activity was suppressed.
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PMID:The link between metabolism and active transport of sodium in human red cell ghosts. 720 43


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