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)

1. The intracellular distribution of hexokinase activity was studied in the mucosa of rat and guinea-pig small intestine. In the rat 60% and in the guinea pig 45% of the hexokinase activity of homogenates were recovered in a total particulate fraction that contained only 5-17% of the homogenate activity of hexose phosphate isomerase, pyruvate kinase, lactate dehydrogenase and overall glycolysis (formation of lactate from glucose). 2. Fractionation of homogenates from guineapig small intestine showed that the particulate hexokinase activity was chiefly in the mitochondrial fraction with a small proportion in the nuclei plus brush-border fraction. 3. After chromatography of the particle-free supernatants on DEAE-cellulose, hexokinase types I and II were determined quantitatively. No evidence was obtained for the presence of hexokinase type III or glucokinase. In the preparations from guinea pigs, hexokinase types I and II amounted to 69% and 31% respectively of the eluted activity; the corresponding values for preparations from rats were 5.8% and 94.2%. 4. Total and specific hexokinase activities decreased significantly in homogenates and particle-free supernatants prepared from the intestinal mucosa of rats starved for 36hr. and increased again after re-feeding. The decrease in hexokinase activity in the particle-free supernatant from starved rats was chiefly due to a decrease in the type II enzyme.
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PMID:Glucose metabolism in the mucosa of the small intestine. A study of hexokinase activity. 566 46

The cellular distribution of hexokinase isoenzymes, N-acetylglucosamine Kinase and pyruvate kinases in rat liver was studied. Hepatocytes and non-parenchymal cells with high viability and almost no cross-contamination were obtained by perfusion in situ of the liver with collagenase, with the use of an enriched cell-culture medium in all steps of cell isolation. Separation of hexokinase isoenzymes was done by DEAE-cellulose chromatography, and enzyme activities were measured by a specific radioassay. Cytosol from isolated hepatocytes contained high-affinity hexokinases A, B and C, in addition to hexokinase D. The last-mentioned represented about 95% of total glucose-phosphorylating activity. Only hexokinase A was found associated t the particulate fraction. Isolated non-parenchymal cells contained only hexokinases A, B and C. N-Acetylglucosamine kinase was measured with a specific radioassay and was found as a single enzyme form in both hepatocytes and non-parenchymal cells, with higher activities in the former. Pyruvate kinase isoenzyme L was present only in the hepatocytes and isoenzyme K only in the non-parenchymal liver cells, confirming that they are good cellular markers.
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PMID:All hexokinase isoenzymes coexist in rat hepatocytes. 608 33

Mg2+-ATPase activity was identified in the cytosol of human erythrocytes. A partial purification of this activity was achieved by an initial DEAE-Sephadex column chromatography, followed by gel filtration on Sephadex G-100 and then a second DEAE-Sephadex chromatography procedure. The enzyme appeared in the void volume of the Sephadex G-100 column and was retained on an Amicon XM100A ultrafiltration membrane. The molecular weight of the enzyme was estimated to be 113 000 from SD gels. The above purification protocol yielded an enzyme with an optimal pH between 7.6 and 8.2. The enzyme activity increased linearly between 30 and 44 degrees C. It was stable for several months at -20 degrees C. Magnesium was essential for activity, but the rate attainable with Mn2+ was at least as great as that due to Mg2+. No other divalent cation was able to substitute for Mg2+ or Mn2+. Neither low nor high Ca2+ concentrations significantly affected the enzymatic activity. Substrate specificity studies showed that ATP was the preferred substrate followed by CTP (46% of the rate produced by ATP). Hydrolysis of GTP, UTP, ITP and ADP was less than 10% of the rate seen with ATP. No phosphatase, pyrophosphatase, phosphodiesterase, hexokinase, phosphofructokinase or adenylate cyclase activity could be detected in this enzyme preparation. Calmodulin, which stimulates the (Ca2+ + Mg2+)-ATPase of the human erythrocyte membrane, failed to enhance the Mg2+-ATPase activity. Of considerable interest, the activity of this Mg2+-ATPase was enhanced approximately 5-fold by low concentrations of mercuric ion, p-hydroxymercuribenzoate and DTNB, but was much less sensitive to iodoacetamide.
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PMID:Partial purification and characterization of a novel Mg2+-dependent ATPase present in the cytosol from human erythrocytes. 615 Jul 30

Hamamelosekinase (ATP:hamamelose 2(1)-phosphotransferase) was purified from a crude extract of Kluyvera citrophila 627 (Enterobacteriaeceae) which has been grown on D-hamamelose. Ammonium-sulfate fractionation and twofold chromatography on DEAE-cellulose resulted in a 51-fold purification of the enzyme. Neither glucosekinase nor significant ATPase activity could be detected in the pure preparation. Besides D-hamamelose only D-hamamelitol was utilized as a substrate; however, the latter was phosphorylated at a very low rate. The molecular weight of the enzyme as estimated by gel chromatography is 21 000. The Km values for hamamelose and ATP were 3 mM nd 2.5 mM, respectively. The pH optimum was found at 7.5. In contrast to hexokinase, purified hamamelosekinase is very labile and could only be stabilized by addition of its substrate D-hamamelose. The most unusual property with respect to yeast hexokinase is a pronounced substrate inhibiton by hamamelose (> 5mM) and ATP (> 7mM), respectively, which could be interpreted as due to an economic utilization of the nutrient. Hamamelosekinase as well as glucosekinase are inducible by growing the microorganisms on the corresponding monosaccharides.
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PMID:Purification and properties of hamamelosekinase. 624 93

The number and nature of glucose-phosphorylating enzymes of rat intestinal mucosa were investigated by chromatographic, electrophoretic, and kinetic methods. Three fractions with glucose-phosphorylating activity were obtained from the supernatant fluid of mucosa homogenate by means of DEAE-cellulose chromatography, corresponding to hexokinases A and B (EC 2.7.1.1.), and N-acetyl-D-glucosamine kinase (EC 2.7.1.59). Although the latter uses N-acetylglucosamine as the main substrate, it is also able to phosphorylate glucose. Electrophoresis in polyacrylamide and in cellulose acetate gels showed the same three enzyme activities. None of these procedures revealed the presence of either hexokinase D ("glucokinase") or hexokinase C in the intestinal mucosa. In the sediment fractions hexokinase A and B, but not N-acetylglucosamine kinase, were found. The Km values for glucose of partially purified hexokinases A and B were 0.025 and 0.174 mM, respectively, and their substrate specificity was the same as that of hexokinases A or B from other tissues. Partially purified N-acetylglucosamine kinase showed hyperbolic saturation functions for N-acetylglucosamine and ATP, with Km values of 0.021 and 0.38 mM, respectively. This enzyme also phosphorylated glucose, mannose, fructose, 2-deoxyglucose, and glucosamine. The dependence of velocity on glucose concentrations was complex, mimicking negative cooperativity. The molecular weight of both hexokinases A and B was 98,000 and that of N-acetylglucosamine kinase was 59,000. The kinetic properties, as well as the chromatographic and electrophoretic mobilities, of N-acetylglucosamine kinase may serve to confuse it with hexokinase D, and thus several criteria should be applied for correct identification.
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PMID:Kinetic, chromatographic and electrophoretic studies on glucose-phosphorylating enzymes of rat intestinal mucosa. 632 88

Glucokinase (ATP:D-glucose 6-phosphotransferase, EC 2.7.1.2) from rat islets of Langerhans was partially purified by chromatography on DEAE-Cibacron blue F3GA agarose. The enzyme eluted in two separate peaks. Sigmoidal rate dependence was found with respect to glucose (Hill coefficient = 1.5) for both enzyme fractions. Km values for glucose were 5.7 mM for the major fraction and 4.5 mM for the minor fraction. Neither fraction phosphorylated GlcNAc. A GlcNAc kinase (ATP:2-acetamido-2-deoxy-D-glucose 6-phosphotransferase, EC 2.7.1.59)-enriched fraction, prepared by affinity chromatography on Sepharose-N-(6-aminohexanoyl)-GlcNAc, had a Km of 25 microM for GlcNAc. Islet tissue also contained hexokinase (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1) eluting in multiple peaks. The results are consistent with the concept that glucokinase serves as the glucose sensor of pancreatic beta cells.
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PMID:Chromatographic resolution and kinetic characterization of glucokinase from islets of Langerhans. 633 76

Hexokinase able to bind to mitochondria was purified to homogeneity from rat brain by two successive DEAE-cellulose chromatographic steps. The enzyme lost only the binding ability with almost undetectable change in molecular weight on mild chymotrypsin digestion. The bindable hexokinase was adsorbed to a Phenyl-Sepharose column and eluted with a Lubrol PX gradient, whereas non-bindable hexokinase and yeast hexokinase were not adsorbed under the similar conditions. These results suggest that mitochondria-bindable hexokinase has a hydrophobic region on its surface, which is responsible for the specific interaction with mitochondria.
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PMID:Difference in hydrophobicity between mitochondria-bindable and non-bindable forms of hexokinase purified from rat brain. 662 21

Ion-filtration chromatography on DEAE-Sephadex A-25 at pH 5.5 resolved the total hexokinase activity in a 27,000g supernatant prepared from developing castor oil (Ricinus communis L., cv. Baker 296) seeds into three distinct peaks. These were designated one, two, and three in order of elution from the column. Ion-filtration chromatography of various subcellular fractions demonstrated that isozyme one is associated with the mitochondria, isozyme two with the leucoplasts, and isozyme three is located in the cytosol. Organelle-subfractionation studies showed that hexokinase one is associated with the mitochondrial outer membrane, and hexokinase two is located in the plastid stroma. Isozyme one could be specifically solubilized from the mitochondrial outer membrane by incubation with nucleoside triphosphates or hexose monophosphates. In addition to differences in net charge and localization, the three hexokinase isozymes could be distinguished by pH optima, substrate specificity, and response to sulfhydryl-directed inhibitors. Mr values, determined by gel permeation using Sephacryl S-200, were identical for all three isozymes at 38,000. The preferred divalent metal ion for each of the hexokinases is Mg+2, and none was affected by Na+, K+, or NH+4 at their pH optima, nor by Al+3 at pH 6.6 or 7.8.
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PMID:Mitochondrial, plastid, and cytosolic isozymes of hexokinase from developing endosperm of Ricinus communis. 663 67

Mitochondrial hexokinases from several rat tissues were analyzed by DEAE-cellulose chromatography. Solubilization by glucose-6-P or Triton X-100 released hexokinases A and B. Solubilization by ATP resulted in a decrease of hexokinase A and the concomitant appearance of a new fraction of lower net charge (hexokinase Am) which readily reverts to hexokinase A by dialysis or dilution. Treatment of homogeneous or partially purified hexokinase A with ATP did not generate hexokinase Am. Hexokinases Am and A were equally inhibited by an anti-hexokinase immune serum and displayed the same Km values for glucose and ATP. Hexokinase Am may represent a conformer or an oligomer produced during ATP-induced solubilization of hexokinase A from mitochondria.
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PMID:A modified form of mitochondrial hexokinase produced by ATP-induced solubilization. 667 48

During gel filtration on Sephadex G-200 human cancerocerebral antigen (CCA) was eluted as two protein fractions with molecular mass of 135,000 and 270.000 daltons. Only one band of protein with molecular mass of about 15,000 daltons was noted after electrophoresis in 10% polyacrylamide gel containing SDS. As characteristic properties of CCA were recognized an electrophoretic polymorphism and a distinct trend to polymerization and isomeria. The antigen was not stained with dyes designed for staining base proteins, lipo-,glyco- and ferroproteins; CCA was thermostable (5 min at 80 degrees), it was inactivated by trypsin and protease but was resistant to pronase, hexokinase, alpha-amylase and beta-glucuronidase. A procedure was developed for isolation of CCA from brain, including fractionation with ammonium sulfate, ion exchange chromatography on DEAE-Sephadex A-50. The procedure enabled to obtain the CCA preparations suitable for radioimmunological, immunobiological assays and amino acid analyses.
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PMID:[Isolation and physico-chemical characteristics of human cancerocerebral antigen]. 671 Sep 41


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