Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.1.1 (hexokinase)
 5,274 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Production of alcohol-free beer by limited fermentation is optimally performed in a packed-bed reactor. This highly controllable system combines short contact times between yeast and wort with the reduction of off-flavors to concentrations below threshold values. In the present study, the influence of immobilization of yeast to DEAE-cellulose on sugar fermentation and aldehyde reduction was monitored. Immobilized cells showed higher activities of hexokinase and pyruvate decarboxylase compared to cells grown in batch culture. In addition, a higher glucose flux was observed, with enhanced excretion of main fermentation products, indicating a reduction in the flux of sugar used for biomass production. ADH activity was higher in immobilized cells compared to that in suspended cells. However, during prolonged production a decrease was observed in NAD-specific ADH activity, whereas NADP-specific activity increased in the immobilized cells. The shifts in enzyme activities and glucose flux correlate with a higher in vivo reduction capacity of the immobilized cells.
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PMID:Influence of yeast immobilization on fermentation and aldehyde reduction during the production of alcohol-free beer. 1079 7

Effects of theophylline, lidocaine, cyclophosphamide, hyoscine N-butyl bromide, tranexamic acid and cytarabine on hexokinase (HK) from human erythrocytes have been investigated in vitro. In addition, in vivo effects of theophylline and lidocaine were investigated in rats. HK was purified from human red blood cells by DEAE-Sephadex A50 ion exchange chromatography. HK activity was measured spectrophotometrically at 25 degrees C in a system coupled with glucose 6-phosphate dehydrogenase, according to Beutler's method at 340 nm. Cyclophosphamide, hyoscine N-butyl bromide, tranexamic acid and cytarabine had no effects on human erythrocyte HK activity in in vitro conditions. On the other hand, human erythrocyte HK was inhibited by theophylline, but activated by lidocaine. IC50 value for theophylline was 0.013 M. In the case of in vivo studies, 6 mg kg(-1) of theophylline inhibited the rat HK activity by 43% at the first 1.5 h (p < 0.001). A dose of 5 mg kg(-1) of lidocaine activated the rat HK activity by 41% (p < 0.001), 22% (p < 0.001), and 11% (p < 0.05), at 1.5, 3 and 6 h, respectively.
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PMID:Some drug effects on the activity of erythrocyte hexokinase and glucose 6-phosphate dehydrogenase enzymes in vitro and in vivo. 1286 23

A full-length hexokinase cDNA was cloned from Solanum chacoense, a wild relative of the cultivated potato. Analysis of the predicted primary sequence suggested that the protein product, ScHK2, may be targeted to the secretory pathway and inserted in the plant plasma membrane, facing the cytosol. ScHK2 was expressed as a hexahistidine-tagged protein in Escherichia coli. Expression conditions for this construct were optimized using a specific anti-hexokinase polyclonal anti-serum raised against a truncated version of ScHK2. The full-length recombinant protein was purified to electrophoretic homogeneity using immobilized metal ion affinity chromatography followed by anion exchange chromatography on Fractogel EMD DEAE-650 (S). The purified enzyme had a specific activity of 5.3 micromol/min/mg protein. Its apparent Kms for glucose (23 microM), mannose (30 microM), fructose (5.2 mM), and ATP (61 microM) were in good agreement with values found in the literature for other plant hexokinases. Hexahistidine-tagged ScHK2 was highly sensitive to pH variations between 7.7 and 8.7. It was inhibited by ADP and insensitive to glucose-6-phosphate. These findings constitute the first kinetic characterization of a homogeneous plant hexokinase preparation. The relevance of ScHK2 kinetic properties is discussed in relation to the regulation of hexose metabolism in plants.
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PMID:Cloning, expression, purification, and properties of a putative plasma membrane hexokinase from Solanum chacoense. 1637 70

The influence of diabetes on the enzyme hexokinase (HK) was examined in the salivary glands of rats. Diabetes was induced by an intraperitoneal injection of streptozotocin (60 mg/Kg body weight) in overnight fasted rats (180-200 g). The animals were killed 48 hours and 30 days after the induction of diabetes and the submandibular and parotid salivary glands extracted for use. Hyperglycemia was evaluated by determining the blood sugar. The area occupied by each intralobular component, acini, ducts, total parenchyma and stroma was measured, and no differences were observed compared with control. In the soluble fraction of the submandibular gland, no difference in the specific activity of HK was observed, between the diabetic and control animals, however, the activity per gland and per g of tissue showed lower values than control. The specific activity of the bound form was reduced in the diabetic gland. The results obtained for the parotid gland were different from the submandibular. The specific activity of both the soluble and bound forms were increased in the diabetic animals. The DEAE-cellulose column chromatography of the soluble and bound forms of the enzyme from both glands showed a first peak appearing during the washing of the column and two other peaks were eluted by the gradient. Thus, three isoenzymes in the submandibular and parotid salivary glands for the control and diabetic rats have been found.
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PMID:Influence of streptozotocin-induced diabetes on hexokinase activity of rat salivary glands. 1644 May 96

In mammals, hexokinase (HK) is strategically located at the outer membrane of mitochondria bound to the porin protein. The mitochondrial HK is a crucial modulator of apoptosis and reactive oxygen species generation. In plants, these properties related to HK are unknown. In order to better understand the physiological role of non-cytosolic hexokinase (NC-HK) in plants, we developed a purification strategy here described. Crude extract of 400 g of maize roots (230 mg protein) contained a specific activity of 0.042 micromol G6P min(-1) mg PTN(-1). After solubilization with detergent two fractions were obtained by DEAE column chromatography, NC-HK 1 (specific activity = 3.6 micromol G6P min(-1) mg PTN(-1) and protein recovered = 0.7 mg) and NC-HK 2. A major purification (yield = 500-fold) was obtained after passage of NC-HK 1 through the hydrophobic phenyl-Sepharose column. The total amount of protein and activity recovered were 0.04 and 18%, respectively. The NC-HK 1 binds to the hydrophobic phenyl-Sepharose matrix, as observed for rat brain HK. Mild chymotrypsin digestion did not affect adsorption of NC-HK 1 to the hydrophobic column as it does for rat HK I. In contrast to mammal mitochondrial HK, glucose-6-phosphate, clotrimazole or thiopental did not dissociate NC-HK from maize (Zea mays) or rice (Oryza sativa) mitochondrial membranes. These data show that the interaction between maize or rice NC-HK to mitochondria differs from that reported in mammals, where the mitochondrial enzyme can be displaced by modulators or pharmacological agents known to interfere with the enzyme binding properties with the mitochondrial porin protein.
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PMID:Partial purification of tightly bound mitochondrial hexokinase from maize (Zea mays L.) root membranes. 1698 Oct 44

Skeletal muscle hexokinase (HK) from Richardson's ground squirrels was analyzed to determine how the enzyme is regulated during hibernation, a state of cold torpor. The HK II isozyme dominated in muscle and ~15% of total HK was bound to the insoluble fraction. HK maximum activity was 33% lower in hibernator muscle and the enzyme showed a significantly higher K ( m ) ATP (by 80%) and a lower K ( i ) for glucose-6-P (by 40%) than euthermic HK (assayed at 22 degrees C). However, 5 degrees C assay significantly reduced K ( m ) glucose of hibernator HK. Stimulation of AMP-dependent protein kinase (AMPK) in hibernator extracts elevated the HK activity and reduced K ( m ) ATP, but did not affect euthermic HK. Stimulation of protein phosphatases significantly lowered the HK activity in both situations. AMPK-dependent phosphorylation was confirmed by immunopreciptiation of (32)P-labeled HK. DEAE-Sephadex ion exchange chromatography revealed two peaks of HK in hibernator muscle extracts (low and high phosphate forms), whereas only a single peak of phospho-HK was present in euthermic muscle. We conclude that differential control of muscle HK in euthermic versus hibernating states is derived from two main regulatory influences, reversible protein phosphorylation and temperature effects on kinetic properties.
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PMID:Skeletal muscle hexokinase: regulation in mammalian hibernation. 1864 17

An ATP: D-glucose and D-mannose 6-phosphotransferase activity was found in Mycobacterium tuberculosis HERa. The activity was separated from other ATP- and polyphosphate D-glucose phosphotransferases in a procedure involving precipitation with ammonium sulfate, treatment with calcium phosphate gel, DEAE-cellulose and DEAE-Sephadex A50 chromatography. The optimum pH of the phosphorylation reaction was from 9 to 10.5. The hexokinase phosphorylated D-glucose with a Km of 20 mM under conditions of MgATP saturation. The Km for MgATP was 0.2 mM. The enzyme showed a higher activity on D-mannose at a saturation level being about 100-fold lower than that of D-glucose; it did not utilize either D-fructose or D-glucosamine. Inorganic poly(P) could not replace ATP as the phosphate donor. M. tuberculosis H37Ra was unable to grow on D-mannose which may suggest that the enzyme studied is involved in endogenous metabolism of this sugar.
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PMID:A mannoglucokinese of Mycobacterium tuberculosis H37Ra. 1985 10


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