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 mannitol cycle is an important NADPH regenerating system in Alternaria alternata. The cycle is built up to the following enzymes: mannitol 1-phosphate dehydrogenase, mannitol 1-phosphatase, mannitol dehydrogenase and hexokinase. The net reaction of one cycle turn is: NADH + NADP+ + ATP leads to NAD+ + NADPH + ADP + Pi. The enzymes needed for an operating cycle were found in Aspergillus, Botrytis, Penicillium, Pyricularia, Trichothecium, Cladosporium and Thermomyces all genera belonging to Fungi Imperfecti. The only genus of this class lacking the cycle was Candida. No genera from the classes Basidiomycetes and Phycomycetes showed any mannitol 1-phosphate dehydrogenase or mannitol 1-phosphatase activities. The genera investigated, belonging to Ascomycetes, Gibberella, Ceratocystis and Neurospora all lacked mannitol 1-phosphate dehydrogenase. It was concluded that the mannitol cycle is an important and widespread pathway for NADH oxidation and NADP+ reduction in the organisms belonging to the class Fungi Imperfecti.
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PMID:The distribution of the NADPH regenerating mannitol cycle among fungal species. 678 99

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

We report a new statistical tool for comparing several dry-reagent strip procedures for whole blood glucose, which produce data in both digital and ordinal form, with results by the well-studied hexokinase-glucose-6-phosphate dehydrogenase procedure coupled to NAD+-NADH. Our use of "ordinal comparison unit" allows for a more equitable comparison of such data. These strip procedures produce biases of -2.21 to 1.74 ordinal comparison units over the range of glucose values corresponding to hypoglycemia and hyperglycemia, as compared with results by the hexokinase procedure, but they are essentially equivalent when compared with each other.
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PMID:Statistical comparison of blood glucose as determined by several test-strip procedures and by a hexokinase procedure. 684 48

Clones of 32 strains of Trichomonas vaginalis isolated from patients attending a venereal diseases clinic were compared among themselves and with authentic Pentatrichomonas hominis on the basis of their isoenzyme patterns for eight enzymes by thin-layer starch-gel electrophoresis. The enzymes examined were: glucose phosphate isomerase (GPI); phosphoglucomutase (PGM); malic enzyme (NADP+) (ME); hexokinase (HK); malate dehydrogenase (NAD+) (MDH); glucose-6-phosphate dehydrogenase (G6PD); aldolase (ALD); and lactate dehydrogenase (LDH). From the isoenzyme patterns of four enzymes (LDH, MDH, HK, and GPI) the strains of T vaginalis could be divided clearly into five groups. PGM showed differences in only one strain, while two other enzyme patterns (ME and ALD) were the same for all the strains of T vaginalis tested. All isolates were clearly distinguishable from P hominis. Although G6PD patterns were not sharp some differences were evident among T vaginalis strains.
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PMID:Isoenzyme characterisation of Trichomonas vaginalis. 698 Jun 85

A number of reactive dichlorotriazine dyes specifically and irreversibly inactivate pig heart lactate dehydrogenase, yeast glucose 6-phosphate dehydrogenase and yeast hexokinase at sites competitive with NAD+, NADP+, and ATP respectively. Monochlorotriazine dyes, including Cibacron Blue F3G-A, do not inactivate lactate dehydrogenase but display high affinity and thus inhibit the inactivation by dichlorotriazine dyes. These data are interpreted in terms of the ability of nucleotide-binding enzymes to bind polysulphonated aromatic chromophores.
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PMID:Triazine dyes, a new class of affinity labels for nucleotide-dependent enzymes. 700 86

With few exceptions, the specific activities of the glycolytic enzymes and the steady-state content of glycolytic and associated intermediates in protoscoleces of the horse (E.g.H) and sheep (E.g.S) strains of Echinococcus granulosus and the closely related E. multilocularis (E.m.) are very similar. Phosphorylase, hexokinase, phosphofructokinase and pyruvate kinase catalyse non-equilibrium reactions and the patterns of activity for pyruvate kinase, phosphoenolypyruvate carboxykinase and malic enzyme are similar in the three organisms. The levels of tricarboxylic acid cycle intermediates in E.g.H., E.g.S. and E.m. are of the same order as those reported in tissues with an active cycle. Each has a complete sequence of cycle enzymes but there are substantial differences between the three parasites with regard to the activity of individual enzymes. The activities of NAD and NADP-linked isocitrate dehydrogenases are significantly lower in E.g.H. than in E.g.S. and particularly in E.m. which suggests that the tricarboxylic acid cycle may play a more important role in carbohydrate metabolism and energy production in the latter parasites. Nevertheless, the three organisms utilize fermentative pathways for alternative energy production, fix carbon dioxide via phosphoenolpyruvate carboxykinase and have a partial reversed tricarboxylic acid cycle. It is speculated that in vivo more carbon will be channelled towards oxaloacetate than pyruvate at the phosphonenolpyruvate branch point. The steady state content of ATP and the ATP/AMP ratios are low in the three organisms, suggesting a low rate of ATP utilization in each.
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PMID:Intermediary carbohydrate metabolism in protoscoleces of Echinococcus granulosus (horse and sheep strains) and E. multilocularis. 707 Aug 45

Regulation of glucose metabolism in glycolysis by round spermatids was studied. Assay of activities of 11 glycolytic enzymes in cell-free spermatid extracts showed that hexokinase, phosphofructokinase, and glyceraldehyde-3-phosphate dehydrogenase had the lowest activities. When the cells were incubated with glucose (10 mM), the intracellular level of ATP fell rapidly and 5'-AMP increased. The ADP level remained unchanged. During incubation with glucose, fructose-1,6-bisphosphate, dihydroxyacetone phosphate, and glyceraldehyde-3-phosphate were accumulated without any change in a mass action ratio of fructose bisphosphate aldolase. Glyceraldehyde-3-phosphate dehydrogenase appeared to play a regulatory role in glycolysis. Glyceraldehyde-3-phosphate dehydrogenase was inhibited by the following compounds (Ki values in parentheses): adenosine (4.34 mM), 5'-AMP (3.50 mM), ADP (2.35 mM), ATP (5.34 mM), and 3',5'-cAMP (0.60 mM). In each case, the inhibition was competitive with NAD (Km = 0.20 mM). The 2'-hydroxy group of the adenine-linked ribose moiety was essential for binding. The compounds adenine, 2'-deoxyadenosine, 2'-AMP, 3'-AMP, CTP, GTP, UTP, and NADP showed little inhibition. These findings suggest that regulation of glycolysis in round spermatids by glyceraldehyde-3-phosphate dehydrogenase is most likely and that glyceraldehyde-3-phosphate dehydrogenase is inhibited by the adenine nucleotides, particularly by 5'-AMP and ADP as inhibitors competitive with NAD.
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PMID:Regulation of glucose metabolism by adenine nucleotides in round spermatids from rat testes. 714 87

The mechanism of the in vitro PGBx effect on mitochondria was studied by determining the specific requirements of the assay system composition. These studies showed that (a) rat liver mitochondria must first be exposed to hypotonic media containing PGBx under aerobic conditions, (b) oxygen, Pi, Mg++, phosphate acceptor (nucleotides), and some oxidizable substrates are essential components to yield optimal phosphorylation values. KCl and bovine serum albumin are non-essential components. With regard to nucleotide acceptor specificity, the AMP, ADP, and glucose-ADP-hexokinase systems were satisfactory. With regard to substrate specificity, only beta-hydroxybutyrate and externally reduced NAD+ were unsatisfactory. The requirement for oxygen was twofold: (a) as an absolute requirement for oxidative phosphorylation, and (b) as a requirement for the hypotonic degradation of mitochondria. These results suggest that PGBx reacts with mitochondria to "protect" against degradation during aerobic hypotonic exposure.
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PMID:Mechanism of polymeric prostaglandin PGBx for in vitro stabilization of rat liver mitochondrial oxidative phosphorylation. 718 41

Two major hexokinases (ATP: D-hexose 6-phosphotransferases, EC 2.7.1.1) have been identified in tissues of Homarus americanus (lobster) and separated from each other by DEAE-cellulose ion-exchange chromatography and by polyacrylamide gel electrophoresis. The molecular weight of each, determined by gel filtration, is about 50 000. Hexokinase II, named for its column elution order, resembles hexokinase isozymes I and II of vertebrates. Km values for glucose, mannose and fructose are 0.08, 0.13 and 6.7 mM, respectively. It is strongly inhibited by the reaction products, ADP and glucose-6-P (Ki = 0.8 mM). Hexokinase I appears to be different from any animal hexokinase previously described. It has a high affinity for mannose and fructose and low affinity for glucose. Km values are 6, 0.07 and 1.2 mM and relative maximum rates 100, 520 and 1070 for glucose, mannose and fructose, respectively. Hexokinase I is not inhibited by physiological concentrations of ATP nor by glucose-6-P , mannose-6-P or fructose-6-P even at high concentrations. Both enzymes occur in muscle at about 10% of the concentration found in the hepatopancreas. The use of Leuconostoc mesenteroides glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate: NADP+ 1-oxidoreductase, EC 1.1.1.49), with NAD as cofactor, is recommended for measuring hexokinases in crude tissue preparations to avoid the variable further reduction of nucleotide caused by the action of 6-phosphogluconate dehydrogenase when NADP is used with yeast glucose-6-phosphate dehydrogenase.
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PMID:Two hexokinases of Homarus americanus (lobster), one having great affinity for mannose and fructose and low affinity for glucose. 721 58

Rat liver cytoplasm (postnuclear supernatant) has a low aerobic glycolytic rate in the presence of added glucose, ATP, ADP, Pi, and NAD+, whereas cytoplasm from Ehrlich ascites tumor cells exhibit a high aerobic glycolytic rate which is typical of rapidly proliferating tumor cells. Tumor mitochondria, unlike liver mitochondria, contain bound hexokinase which constitutes about 70% of the total cellular hexokinase activity. The high aerobic glycolytic rate of Ehrlich tumor cytoplasm is reduced markedly if the mitochondria are removed and can be restored almost completely upon addition of the hexokinase-containing tumor mitochondria to tumor cytosol (postmitochondrial supernatant). Addition of tumor mitochondria to liver cytosol can enhance its glycolytic rate to levels approaching those of tumor cytoplasm, whereas added liver mitochondria are without effect on the already low glycolytic rate of liver cytosol. Addition of tumor mitochondria to tumor cytosol increases its glycolytic rate to the level of tumor cytoplasm, as mentioned above, but liver mitochondria added to tumor cytosol actually depress its glycolytic rate to the level of liver cytosol. The stimulatory effect of tumor mitochondria on liver cytosol can be ascribed to its associated hexokinase activity since hexokinase specifically removed from mitochondria of tumor cells can also enhance the glycolytic rate of liver cytosol. The depressing effect of added liver mitochondria on tumor cytosol glycolysis suggests that liver mitochondria can compete more effectively than tumor mitochondria for a common intermediate and/or cofactor. Examination of 12 different tumor cell lines revealed that only those which reached maximum size in 1 month or less, and which have elevated glycolytic activities, had detectable mitochondrially associated hexokinase activity. The studies reported here describe resolution and reconstitution of tumor cytoplasm, supplementation of cytosol with intact mitochondria or mitochondrial hexokinase, and a survey of mitochondrial hexokinase content in various tumors, and provide strong evidence for the view (Bustamante, E., and Pedersen, P. L. (1977) Proc. Natl. Acad. Sci. U. S. A. 74, 3735-3739) that a form of hexokinase with a propensity for mitochondrial binding plays a key role in the high aerobic glycolysis of cancer cells.
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PMID:Energy metabolism of tumor cells. Requirement for a form of hexokinase with a propensity for mitochondrial binding. 726 78


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