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)

A protease from Tetrahymena pyriformis inactivated eight of nine commercially available enzymes tested, including lactate deyhdrogenase, isocitrate dehydrogenase (TPN-specific), glucose-6 phosphate dehydrogenase, D-amino acid oxidase, fumarase, pyruvate kinase, hexokinase, and citrate synthase. Urate oxidase was not inactivated. Inactivation occurred at neutral pH, was prevented by inhibitors of the protease, and followed first order kinetics. In those cases tested, inactivation was enhanced by mercaptoethanol. Most of the enzyme-inactivating activity was due to a protease of molecular weight 25,000 that eluted from DEAE-Sephadex at 0.3 M KCl. A second protease of this molecular weight, which was not retained by the gel, inactivated only isocitrate dehydrogenase and D-amino acid oxidase. These two proteases could also be distinguished by temperature and inhibitor sensitivity. Two other protease peaks obtained by DEAE-Sephadex chromatography had little or no no enzyme inactivating activity, while another attacked only D-amino acid oxidase. At least six of the enzymes could be protected from proteolytic inactivation by various ligands. Isocitrates dehydrogenase was protected by isocitrate, TPN, or TPNH, glucose-6-dehydrogenase by glucose-6-P or TPN, pyruvate kinase by phosphoenolypyruvate or ADP, hexokinase by glucose, and fumarase by a mixture of fumarate and malate. Lactate dehdrogenase was not protected by either of its substrates of coenzymes. Citrate synthase was probably protected by oxalacetate. Our data suggest that the protease or proteases discussed here may participate in the inactivation or degradation of a least some enzymes in Tetrahymena. Since the inactivation occurs at neutral pH, this process could be regulated by variations in the cellular levels of substrates, coenzymes, or allosteric regulators resulting form changes in growth conditions or growth state. Such a mechanism would permit the selective retention of enzymes of metabolically active pathways.
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PMID:Enzyme inactivation by a cellular neutral protease: enzyme specificity, effects of ligands on inactivation, and implications for the regulation of enzyme degradation. 1 68

ATP and citrate, the well known inhibitors of phosphofructokinase (ATP: D-fructose 6-phosphate 1-phosphotransferase, EC 2.7.1.11), were found to inhibit the activities of the multiple forms of phosphoglucomutase (alpha-D-glucose 1,6-bisphosphate: alpha-D-glucose 1-phosphate phosphotransferase, EC 2.7.5.1) from rat muscle and adipose tissue. This inhibition could be reversed by an increase in the glucose 1,6-bisphosphate (Glc-1,6-P2) concentration. Other known activators (deinhibitors) of phosphofructokinase, viz. cyclic AMP, AMP, ADP or Pi, had no direct deinhibitory action on the ATP or citrate inhibited multiple phosphoglucomutases. Cyclic AMP and AMP, could however lead indirectly to deinhibition of the phosphoglucomutases, by activating phosphofructokinase which catalyzes the ATP-dependent phosphorylation of glucose 1-phosphate to form Glc-1,6-P2, the la-ter then released the multiple phosphoglucomutases from ATP or citrate inhibition. The Glc-1,6-P2 was also found to exert a selective inhibitory effect on hexokinase (ATP: D-hexose 6-phosphotransferase, EC 2.7.1.1) type II, the predominant form in skeletal muscle. This selective inhibition by Glc-1,6-P2 was demonstrated on the multiple hexokinases which were resolved by cellogel electrophoresis or isolated by chromatography on DEAE-cellulose. Based on the in vitro studies it is suggested that during periods of highly active epinephrine-induced glycogenolysis in muscle, the Glc-1,6-P2, produced by the cyclic AMP-stimulated reaction of phosphofructokinase with glucose 1-phosphate, will release the phosphoglucomutases from ATP or citrate inhibition, and will depress the activity of muscle type II hexokinase.
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PMID:Complementarity in the regulation of phosphoglucomutase, phosphofructokinase and hexokinase; the role of glucose 1,6-bisphosphate. 12 9

Activities of hexokinase isozymes in carbon tetrachloride (CCl(4))-injured rat liver were determined quantitatively by DEAE-cellulose column chromatography and compared with those of regenerating liver, fetal liver and ascites hepatoma cells (AH 130). The CCl(4)-injured liver revealed an isozyme distribution with predominant Types I, II and III (3.2, 8.8 and 6.8 times higher than the control values, respectively) and with undetectable activity of Type IV hexokinase (glucokinase). Although the isozyme pattern generally resembled that of fetal liver or hepatoma cells, the relatively high activity of hexokinase Type III in CCl(4) treatment characterizes the pattern of hexokinase isozyme in acue liver damage.
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PMID:Hexokinase isozyme pattern in CCl(4)-injured rat liver. 16 18

Four isoenzymes of hexokinase were isolated by means of chromatography on DEAE-cellulose from soluble fraction of Vistar rat liver tissue. One of the isoenzymes (IV) was a glucokinase. Four fractions were also found in starch gel electrophoresis. These fractions catalyzed phosphorylation of glucose. Besides alterations in the total activity of hexokinase the changes in isoenzyme spectra were observed in carcinogenesis, caused by diethyl nitrosoamine. In the course of development of the blastomatose process in liver tissue content of isoenzymes I, II and, especially, of III was increased, and content of isoenzyme IV was decreased. In tissue of primary hepatomas, induced by diethyl nitrosoamine, the isoenzyme spectra of hexokinase did not significantly differ from the spectra of the enzyme in liver tissue at later stages of carcinogenesis.
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PMID:[Liver hexokinase isoenzymes in carcinogenesis]. 16 15

1. ATP-D-hexose-6-phosphotransferase activity was measured in red blood cells of man, rabbit, pig and cow. Mean values ranged from 0.60 to 1.06 units/g haemoglobin and no significant difference was obtained with different glucose concentrations. 2. The characteristics of glucose phosphorylating activities in red blood cells of the species studied were similar. 3. Chromatography on DEAE column revealed two different glucose phosphorylating activities in red cells of man, rabbit and pig, and only one in cow red cells. 4. The first hexokinase activity is the predominant form and is saturated with low glucose concentrations; the second is noticeably marked at high glucose concentrations.
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PMID:Comparative studies on red blood cell glucose phosphorylating activities of mammals. 31 47

1. Angiostrongylus cantonensis contains a glucokinase which was isolated by DEAE-cellulose column chromatography. 2. This enzyme has a much higher affinity toward glucose (apparent Km, 0.2 mM) than fructose (apparent Km, 85 mM). Glucose-6-phosphate (10 mM) does not inhibit glucose phosphorylation. 3. Molecular weight obtained by a molecular sieve chromatography (60,000) is also close to the value of mammalian glucokinase. 4. While Vmax value for mannose is one-third smaller than that for glucose, Km for mannose is rather lower than that for glucose. 5. In addition to the cytosol enzyme, a particle bound hexokinase is found in the worm.
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PMID:Hexokinase of Angiostrongylus cantonensis: presence of a glucokinase. 31 15

The isozymes of hexokinase in surgical specimens of human subcutaneous adipose tissue were separated by elution from DEAE-cellulose with linear KCl gradients at ph 7.4. Two peaks of activity were found: Peak 1 eluted at 0.05M KCl, and Peak 2 at 0.19M KCl. Michaelis constants (Km) for glucose were: Peak 1, 6.5 x 10-5M; Peak 2, 1.5 x 10-4M. Peak 2 was more susceptible than Peak 1 to inactivation by trypsin, 0.1 mg/ml, and was protected by 0.1M glucose. Both peaks were protected from heat inactivation (45 degrees) by 0.1M glucose. Peak 2 comprised 66 +/- 5 percent of the total hexokinase activity. No activity with the characteristics of hexokinase III was detected in human fat. In all these characteristics, the isozymes of human adipose tissue closely resemble hexokinases I and II from rats.
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PMID:Hexokinase isozymes of normal human subcutaneous adipose tissue. 68 73

Three glucose-phosphorylating enzymes having different specificities for glucose and fructose were separated from the cell-free extract of Candida tropicalis by means of ammonium sulfate fractionation and chromatography on DEAE-cellulose and Sephadex G-100. Two of them, which phosphorylated fructose 1.5 times faster than glucose, were designated as hexokinase I and II (ATP : D-hexose 6-phosphotransferase, EC 2.7.1.1.), and the other with very low or no fructose-phosphorylating activity, as glucokinase (ATP : D-glucose 6-phosphotransferase, EC 2.7.1.2). Km values for glucose with both hexokinase I and glucokinase were 0.3 mM, and that for fructose with hexokinase I was 2.2 mM. Time-course changes in the levels of these enzymes in C. tropicalis growing on glucose and on n-alkane revealed that hexokinase was induced specifically by the sugars, while glucokinase was a constitutive enzyme. Addition of cycloheximide to the culture medium prevented the increase in the hexose-phosphorylating activity and in the Fru/Glu ratio (the ratio of enzymatic phosphorylation of fructose to that of glucose) in the cells. Although Candida lipolytica also contained hexokinase and glucokinase, both enzymes seemed to be constitutive.
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PMID:Glucose-phosphorylating enzymes of Candida yeasts and their regulation in vivo. 83 48

In this paper we report the purification of pig erythrocyte hexokinase type III, at preparative level, using 52 liters of starting material (hemolysate). This was possible using a new efficient anion exchanger support, the Toyopearl DEAE 650 M which allows completely to change the strategy of removing hemoglobin from hemolysates, permitting to handle large amounts of starting material and reducing work would have required months using conventional anion exchanger supports, to only 2-3 days. Furthermore, we have tested the binding of other red blood cell enzymes to the Toyopearl DEAE 650 M, showing a wider potential use of this chromatographic support for their purification at a preparative level.
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PMID:Preparative purification of pig red blood cell hexokinase type III using a new efficient chromatographic support. 162 Jun 86

The yeast hexokinase isoenzymes PI and PII have been purified in large amounts (20 mg) from overproducing yeast strains. The purification procedures of hexokinase PI and PII include anion-exchange chromatography on DEAE-Sephacel and chromatofocusing on PBE 94, hydrophobic interaction chromatography on phenyl-Sepharose (necessary for the isolation of the isoenzyme PI); in the final step either a Mono Q HR 5/5 or a Fractogel EMD TMAE 650(S) column was used. Hexokinase preparations were characterized before crystallization by chromatofocusing on a Mono P HR 5/20 FPLC column, where different forms of hexokinase can be rapidly distinguished by their elution behaviour. From both purified hexokinase PI and PII, large crystals were grown that diffract X-rays to high resolution.
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PMID:Purification and crystallization of yeast hexokinase isoenzymes. Characterization of different forms by chromatofocusing. 178 64


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