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

---

Query: EC:2.7.1.1 (hexokinase)
5,274 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1) The activities of 16 enzymes of glycolysis and of glutathione metabolism were determined in intact human red cell membranes (ghosts) which were prepared by hypotonic hemolysis. 2) Enzymes and hemoglobin of the ghosts were resolved by two toluene extractions. Only the four enzymes hexokinase, fructose-bisphosphate aldolase, glyceraldehyde-phosphate dehydrogenase and pyruvate kinase could not be released completely from the ghosts. 3) The residual membrane fraction, which was obtained after the toluene extraction of ghosts prepared at 30 imOsM, contained 0.02% of the original hemoglobin content of the red cell. Between 6.5 and 23% of the hemolysate activities of glyceraldehyde-phosphate dehydrogenase, phosphoglycerate kinase, pyruvate kinase and fructose-bisphosphate aldolase were detected in this fraction after mechanical disruption. 4) Sonication of intact ghosts increased the activities of fructose-bisphosphate aldolase, pyruvate kinase and phosphoglycerate kinase. 5) In "white" ghosts prepared at 5 imOsM phosphate buffer which contained 0.5% of the original hemoglobin the activities of fructose-bisphosphate aldolase and glyceraldehyde-phosphate dehydrogenase were detected at high levels. The activities of pyruvate kinase and phosphoglycerate kinase were low in these preparations. 6) The results indicate that one part of all enzymes is loosely attached to the inner surface of the membrane as is hemoglobin. A second part, the "cryptic enzyme activity", is available after resolving by toluene. A residual part of four enzymes is firmly bound to the membrane. Two of them (fructose-bisphosphate aldolase and glyceraldehyde-phosphate dehydrogenase) are oriented toward the inner surface of the membrane, whereas pyruvate kinase and phosphoglycerate kinase are hidden in the lipid core of the membrane.
...
PMID:Organization of enzymes of glycolysis and of glutathione metabolism in human red cell membranes. 16 42

Several glycolytic enzymes were observed to have between 40-90% of their activities associated with the particulate fractions of lysed nerve endings. The enzymes showing high particulate activity in lysed nerve endings were hexokinase (EC 2.7.1.1), aldolase (EC 4.1.2.13), glucosephosphate isomerase (EC 5.3.1.9), phosphofructokinase (EC 2.7.1.11), glyceraldehyde-phosphate dehydrogenase (EC 1.2.1.12), pyruvate kinase (EC 2.7.1.40) and lactate dehydrogenase (EC 1.1.27). With the exception of phosphofructokinase, 80% or more of the particle associated activity of each enzyme was solubilized by salt treatment indicating the association with particles was ionic. Sub-fractionation of lysed nerve endings showed hexokinase and fumarase (EC 4.2.1.2) had the highest specific activity in the same fractions which is consistent with observations indicating that hexokinase is associated with mitochondria. The other glycolytic zymes having high particulate activity, aldolase, glucosephosphate isomerase, phosphofructokinase, glyceraldehyde-phosphate dehydrogenase, pyruvate kinase and lactate dehydrogenase, showed enrichment in fractions containing synaptosomal membranes, i.e. the fractions having highest specific activity of acetylcholinesterase (EC 3.1.1.7) and (Na+ + K+)-ATPase (EC 3.6.1.3).
...
PMID:Association of glycolytic enzymes with particulate fractions from nerve endings. 62 35

In this communication the results of applying various histochemical semipermeable membrane techniques to the localization of several enzymes in bovine and porcine heart are presented. The Purkinje fibers of the atrioventricular conducting system of the bovine heart differ from the myocardium proper in containing a greater activity of the glycolytic and gluconeogenetic enzymes--lactate dehydrogenase, glyceraldehyde-phosphate dehydrogenase, hexokinase, glucosephosphate isomerase and phosphoglucomutase, and less activity of the aerobic enzymes--NADH: nitroBT oxidoreductase and isocitrate dehydrogenase (NADP+). The metabolic reactions obtained with Purkinje fibers of the porcine heart are less pronounced. These histochemical findings are in accordance with the impression that Purkinje fibers, compared with the common myocardial fibers, have a higher rate of anaerobic metabolism and a lower rate of aerobic metabolism. The activity of the NADPH regenerating enzymes glucose-6-phosphate dehydrogenase and phosphogluconate dehydrogenase (decarboxylating), and the activity of acid hydrolases such as non-specific esterase and acid phosphatase is higher in the Purkinje fibers of both the bovine and porcine heart.
...
PMID:Enzyme histochemical studies on the Purkinje fibers of the atrioventricular system of the bovine and porcine hearts. 66 82

Optimal concentrations of the essential components for analyzing the activity of each enzyme associated with glycolysis and gluconeogenesis in rabbit periodontal ligament were examined, and enzyme assay systems for 15 enzymes including 22 reactions were established using triethanolamine buffer. Specific activities of all the enzymes, except for the gluconeogenic reaction of phosphoglycerate kinase, were systematically evaluated using the optimum buffer for each enzyme, since the activity of each enzyme varied depending on the buffer used. For glycolysis, the activity levels of hexokinase and 6-phosphofructokinase were very low, and consequently these enzyme reactions were inferred to be the rate-limiting steps. For gluconeogenesis, fructose 1,6-bisphosphatase and aldolase activities were extremely low, and the activities of glucose 6-phosphatase, phosphoenolpyruvate carboxykinase and pyruvate carboxylase were undetectable. These results suggest that the periodontal ligament may have no gluconeogenesis capability. With a rise in pH, the activities of the key enzymes of glycolysis gradually increased, and a specific "crossover" point was found between the activities of glyceraldehyde-phosphate dehydrogenase and phosphoglyceromutase. In addition, the activity of fructose 1,6-bisphosphatase, one of the key enzymes of gluconeogenesis, was markedly increased with a rise in pH, although pH changes had no effect on aldolase activity. Consequently, alkaline pH appeared to result in overall stimulation of glycolysis.
...
PMID:Enzymatic regulation of glycolysis and gluconeogenesis in rabbit periodontal ligament under various physiological pH conditions. 165 53

A number of phosphorylated aminosugars have been prepared and tested as substrates for metabolic reactions. 6-Aminoglucose is a slow substrate for yeast hexokinase with a Vmax that is only 0.012% that for glucose. While Vmax is pH independent, V/K decreases below the pK of 9.0 of the amino group. 6-Aminoglucose is a competitive inhibitor vs glucose with a Ki value increasing below the pK of 9 but leveling off at 33 mM below pH 7.16. Thus, protonation decreases binding affinity by 2.4 kcal/mol and only the neutral amine is catalytically competent. 6-Aminoglucose-6-P was synthesized enzymatically with hexokinase. Its pK's determined by 31P NMR were 2.46 and 8.02 (alpha anomer) and 2.34 and 7.85 (beta anomer), with a beta:alpha ratio of 3.0. It is most stable at pH 12 (half-life 228 h at 22 degrees C), while as a monoanion its half-life is 3 h. The free energy of hydrolysis at 25 degrees C and pH 9.25 is -10.3 kcal/mol. The phosphorylated amino analogues of 6-P-gluconate, ribulose-5-P, fructose-6-P, fructose-1,6-bis-P (amino group at C-6 only), and glyceraldehyde-3-P were synthesized enzymatically. The 31P NMR chemical shifts of these analogues are 8-8.5 ppm at pH 9.5. Their relative stability is 6-aminogluconate-6-P greater than 3-aminoglyceraldehyde-3-P greater than 6-aminoglucose-6-P greater than 6-aminofructose-1,6-bis-P congruent to 6-aminofructose-6-P greater than 5-aminoribulose-5-P. These analogues were tested as substrates for their respective enzymes.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Phosphorylated aminosugars: synthesis, properties, and reactivity in enzymatic reactions. 182 91

A study on the enzyme activity of glucose metabolism in the lymphocytes of patients with solid malignant tumors is reported. The results have shown a 30% mean increase of the hexokinase (HK) activity in patients with solid malignant tumors as compared to the mean value observed in a group of healthy subjects. A relationship between level of HK increase and stage of tumor was also observed. The other examined enzyme activities, phosphofructokinase (PFK), pyruvate-kinase (PK), phosphoglycerate-kinase (PGK), phosphoglucoisomerase (PGI), glyceraldehyde-phosphate dehydrogenase (GAPD) glucose-6-phosphate dehydrogenase (G-6PD), 6-phosphogluconate dehydrogenase (6-PGD) and enolase did not show significant changes. It is concluded that even though the use of HK as tumor marker cannot be hypothesized at the present time, a significant relation between an increased activity of this enzyme and presence of the tumor is unquestionable. Therefore, this biochemical effect induced away from the neoplastic tissue deserves further study.
...
PMID:Solid tumors and enzyme activity in human lymphocytes. 283 4

We have developed a method for the simultaneous purification of hexokinase, glucosephosphate isomerase, phosphofructokinase, fructose-1,6-bisphosphate aldolase, triosephosphate isomerase, D-glyceraldehyde-phosphate dehydrogenase, phosphoglycerate kinase, glycerol-3-phosphate dehydrogenase and glycerol kinase from Trypanosoma brucei in yields varying over 8-55%. Crude glycosomes were prepared by differential centrifugation of cell homogenates. Subsequent hydrophobic interaction chromatography on phenyl-Sepharose resulted in six pools containing various mixtures of enzymes. These pools were processed via affinity chromatography (immobilized ATP), hydrophobic interaction chromatography (octyl-Sepharose) and ion-exchange chromatography (CM- and DEAE-cellulose) which resulted in the purification of all nine enzymes. The native enzyme and subunit molecular masses, as determined by gel filtration and gel electrophoresis under denaturing conditions, were compared with those of their homologous counterparts from other organisms. Trypanosomal hexokinase is a hexamer and differs in subunit composition from the mammalian enzymes (monomers) as well as in subunit size (51 kDa versus 96-100 kDa, respectively). Phosphofructokinase only differs in subunit size (51 kDa for T. brucei versus 80-90 kDa for mammals) but had identical subunit composition (tetrameric). The others all have the same subunit composition as their mammalian counterparts. Except for triosephosphate isomerase, all Trypanosoma enzymes have subunits which are 1-5 kDa larger in size. Together these nine enzymes contribute 3.3 +/- 1.6% to the total cellular protein of T. brucei and at least 90% to the total glycosomal protein. A comparison of calculated intraglycosomal concentrations of the enzymes with the glycosomal metabolite concentrations shows that in the case of aldolase, glyceraldehyde-phosphate dehydrogenase and phosphoglycerate kinase, the concentration of active sites is of the same order of magnitude as that of their reactants. A common feature of the glycosomal glycolytic enzymes (with the exception of glucosephosphate isomerase) is that they are highly basic proteins with pI values between 8.8 and 10.2, values which are 1-4 higher than in the case of their mammalian cytosolic counterparts and 3-6 higher than in the case of the various unicellular organisms. It is suggested that both the larger subunit size and the basic character of the T. brucei glycolytic proteins are involved in the routing of the enzymes from their site of biogenesis (the cytosol) towards their site of action (the glycosome).
...
PMID:Glycolytic enzymes of Trypanosoma brucei. Simultaneous purification, intraglycosomal concentrations and physical properties. 294 90

In normal suckling-weanling mice, DL-beta-hydroxybutyrate (30 mmol/kg ip) stimulated insulin secretion and reduced plasma glucose levels. In the brains of these animals, glucose levels were tripled due to a reduced rate of glucose utilization (determined by deoxyglucose phosphorylation). Other metabolite changes were compatible with inhibition of hexokinase, phosphofructokinase, glyceraldehyde-P-dehydrogenase, and pyruvate dehydrogenase activities. In contrast to the decrease in cerebral glycolysis, metabolite changes were compatible with an increase in the Krebs citric acid metabolic flux. The brain energy charge was also elevated. While it is generally believed that ketone bodies cannot sustain normal brain metabolism and function in the absence of glucose, DL-beta-hydroxybutyrate (20 or 30 mmol/kg ip) reversed insulin (100 U/kg sc)-induced hypoglycemia despite the persistence of a critically reduced plasma glucose concentration and near-zero brain glucose levels. Metabolic correlates of possible significance in the behavioral recovery from coma were reductions of the elevated levels of brain aspartate to below normal and ammonia levels to normal. Levels of acetyl CoA were unchanged both before and after treatment with beta-hydroxybutyrate.
...
PMID:Beta-hydroxybutyrate reverses insulin-induced hypoglycemic coma in suckling-weanling mice despite low blood and brain glucose levels. 333 63

Human platelets were separated by desity-centrifugation into heavy and light populations. Heavy platelets have an average volume approximately twofold greater than light platelets, and have previously been shown to be young platelets. All 11 enzymes of the Embden-Meyerhof pathway plus the five related enzymes: phosphoglucomutase, glucose-6-P dehydrogenase, 6-P-gluconic dehydrogenase, alpha-glycerol-P dehydrogenase, and glutathione reductase (TPNH) were examined in cell lysates from total, heavy, and light platelet populations. Apparent Km for individual enzymes were measured in a total platelet population. Empirical V(max) of the individual enzymes were measured in total, heavy, and light platelet populations. The three apparent rate-limiting enzymes for glycolysis were hexokinase, phosphofructokinase, and glyceraldehyde-3-P dehydrogenase. Heavy platelets contained approximately twofold greater enzyme activity (per gram wet weight) than light platelets for 7 of the 16 enzymes measured: hexokinase, phosphohexoisomerase, phosphofructokinase, glyceraldehyde-3-P dehydrogenase, phosphoglycerokinase, lactic dehydrogenase, and phosphoglucomutase. Heavy platelets also contained 1.9-fold greater reduced glutathione (GSH), 1.7-fold greater DPNH, and 1.2-fold greater TPNH than light platelets. Heavy platelets contained 1.8-fold less lipid peroxidation products (malonyl aldehyde equivalents) than light platelets and were 2.4-fold more resistant to lipid peroxidation catalyzed by 0.1 mM FeCl(3). Sterile incubation of heavy platelets, in vitro for 17 hr, resulted in a significant loss of enzyme activity for the "elevated" seven enzymes when compared with the remainder. Reducing agents such as GSH (0.1 mM), ascorbic acid (0.1 mM), and dithiothreitol (0.01 mM), when added to the incubation mixture, significantly reduced the in vitro loss of activity. In vitro incubation was also associated with a significant loss of GSH and DPNH and a 1.8-fold increase in lipid peroxidation products.
...
PMID:Heterogeneity of human platelets. V. Differences in glycolytic and related enzymes with possible relation to platelet age. 426 50

We evaluated the possible role of islet glucokinase in controlling the rate of islet glucose metabolism, and thereby the rate of glucose-induced insulin release. The activities of glucokinase, hexokinase, P-fructokinase, and glyceraldehyde-P dehydrogenase were quantitated in sonicated or isotonically homogenized islet preparations using pyridine nucleotide-dependent fluorometric assays. In sonicates, about 1/4 of the islet glucose phosphorylating activity was due to an enzyme with kinetic properties similar to glucokinase; 3/4 of the activity was due to hexokinase. The procedure for determining islet glucokinase activity was improved by centrifuging isotonic islet homogenates at 12,000 x g. The supernatant fraction was enriched for glucokinase. About 1/2 of the glucose phosphorylating activity in this fraction was due to glucokinase and 1/2 was due to hexokinase. The glucokinase activity in islet homogenates was !23 of the activity of hexokinase, 1/40 of the activity of P-fructokinase, and 1/400 of the activity of glyceraldehyde-P dehydrogenase. Detailed concentration dependency curves of glucose and mannose utilization were also obtained with intact isolated pancreatic rat islets. Glucose and mannose usage in islets was governed by two superimposed hyperbolic systems differing in Km and Vmax. A high Km system (Km for glucose 11 mM and for mannose 21 mM) predominated. A low Km system (Km for glucose 215 and for mannose 530 microM) contributed about 15% to the total activity. The available data with intact islets could be rationalized by the existence of two distinct hexose phosphorylating enzymes with differing capacities and kinetic properties. These enzymes, tentatively identified as glucokinase and hexokinase, could coexist in the same cell or could be distributed among different cell types. The possible physiologic significance of these results is discussed, emphasizing the idea of dual control of glycolysis and insulin release by glucokinase and hexokinase. An earlier proposal that glucokinase serves as glucoreceptor of beta-cells [J. Biol. Chem. 243:2730 (1968)] is greatly strengthened by the present studies.
...
PMID:Regulation of glucose metabolism in pancreatic islets. 627 17


1 2 Next >>

---