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 effect of dietary and hormonal variations on the specific activities of hexokinase isoenzymes, N-acetylglucosamine kinase and pyruvate kinase isoenzymes in parenchymal and non-parenchymal liver cells was studied. Hexokinase D was markedly decreased in hepatocytes from animals fasted or fed on the carbohydrate-free diet as well as from diabetic rats, attaining a constant low level of about 17% of normal values. Pyruvate kinase L was also diminished in hepatocytes under the same experimental conditions. In contrast, the three high-affinity hexokinase isoenzymes A, B and C remained without variation in total amount or in their relative proportions in hepatocytes and non-parenchymal liver cells isolated from animals under the various conditions studied. N-Acetylglucosamine kinase activities also did not change either in parenchymal or in non-parenchymal liver cells under all conditions. The results are discussed in relation to the significance of N-acetylglucosamine kinase and the various hexokinase isoenzymes for the phosphorylation of glucose after dietary and hormonal manipulations.
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PMID:Stability of hexokinases A, B and C and N-acetylglucosamine kinase in liver cells isolated from rats submitted to diabetes and several dietary conditions. 608 34

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

The activities of hexokinase isoenzymes I-IV (EC 2.7.1.1) and of N-acetylglucosamine kinase (EC 2.7.1.59) were determined in normal human liver and in alcoholic liver disease and primary biliary cirrhosis after FPLC fractionation of high-speed supernatants on Mono-Q with a linear NaCl gradient. In control human liver the hexokinase activities were: I, 3.6; II, 0.7; III, 3.5, IV, 4.8 (mUnits/mg supernatant protein). The activity of N-acetylglucosamine kinase was 8 mU/mg of protein. In alcoholic liver disease and primary biliary cirrhosis, the activity of hexokinase IV (glucokinase) was suppressed to less than 10% of control activity and the activity of hexokinase I was increased 3-fold. The activity of hexokinase II was increased approximately 7-fold in alcoholic liver disease. The activities of hexokinase III and N-acetylglucosamine kinase were unchanged in cirrhosis. Hexokinase III showed 50% substrate inhibition at 100 mM glucose as compared with 0.5mM glucose. The high activity of hexokinase III in human liver (approximately 50% of the low-Km activity and 70% of glucokinase activity) results in a significant underestimation of glucokinase activity as determined by the conventional spectrometric assay while the activity of N-acetylglucosamine kinase may contribute to an overestimation of glucokinase activity in the radiochemical assay. Furthermore glucokinase is dramatically suppressed in liver disease, which although partly compensated for by the increase in hexokinase I (and II), accounts in part for the well-known glucose intolerance of liver cirrhosis.
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PMID:Hexokinase isoenzymes in normal and cirrhotic human liver: suppression of glucokinase in cirrhosis. 946 41

Hexokinase catalyzes the phosphorylation of glucose to glucose 6-phosphate by using ATP as a phosphoryl donor. Recently, we identified and characterized an ATP-dependent hexokinase (StHK) from the hyperthermophilic archaeon Sulfolobus tokodaii, which can phosphorylate a broad range of sugar substrates, including glucose, mannose, glucosamine, and N-acetylglucosamine. Here we present the crystal structures of StHK in four different forms: (i) apo-form, (ii) binary complex with glucose, (iii) binary complex with ADP, and (iv) quaternary complex with xylose, Mg(2+), and ADP. Forms i and iii are in the open state, and forms ii and iv are in the closed state, indicating that sugar binding induces a large conformational change, whereas ADP binding does not. The four different crystal structures of the same enzyme provide "snapshots" of the conformational changes during the catalytic cycle. StHK exhibits a core fold characteristic of the hexokinase family, but the structures of several loop regions responsible for substrate binding are significantly different from those of other known hexokinase family members. Structural comparison of StHK with human N-acetylglucosamine kinase and other hexokinases provides an explanation for the ability of StHK to phosphorylate both glucose and N-acetylglucosamine. A Mg(2+) ion and coordinating water molecules are well defined in the electron density of the quaternary complex structure. This structure represents the first direct visualization of the binding mode for magnesium to hexokinase and thus allows for a better understanding of the catalytic mechanism proposed for the entire hexokinase family.
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PMID:Crystal structures of an ATP-dependent hexokinase with broad substrate specificity from the hyperthermophilic archaeon Sulfolobus tokodaii. 1722 27

Due to its position at the outermost of glycans, sialic acid is involved in a myriad of physiological and pathophysiological cell functions such as host-pathogen interactions, immune regulation, and tumor evasion. Inhibitors of cell surface sialylation could be a useful tool in cancer, immune, antibiotic, or antiviral therapy. In this work, four different C-3 modified N-acetylmannosamine analogs were tested as potential inhibitors of cell surface sialylation. Peracetylated 2-acetylamino-2-deoxy-3-O-methyl-D-mannose decreases cell surface sialylation in Jurkat cells in a dose-dependent manner up to 80%, quantified by flow cytometry and enzyme-linked lectin assays. High-performance liquid chromatography experiments revealed that not only the concentration of membrane bound but also of cytosolic sialic acid is reduced in treated cells. We have strong evidence that the observed reduction of sialic acid expression in cells is caused by the inhibition of the bifunctional enzyme UDP-GlcNAc-2-epimerase/ManNAc kinase. 2-Acetylamino-2-deoxy-3-O-methyl-D-mannose inhibits the human ManNAc kinase domain of the UDP-GlcNAc-2-epimerase/ManNAc kinase. Binding kinetics of the inhibitor and human N-acetylmannosamine kinase were evaluated using surface plasmon resonance. Specificity studies with human N-acetylglucosamine kinase and hexokinase IV indicated a high specificity of 2-acetylamino-2-deoxy-3-O-methyl-D-mannose for MNK. This substance represents a novel class of inhibitors of sialic acid expression in cells, targeting the key enzyme of sialic acid de novo biosynthesis.
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PMID:A novel approach to decrease sialic acid expression in cells by a C-3-modified N-acetylmannosamine. 2527 18