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Query: EC:3.1.3.9 (glucose-6-phosphatase)
 3,081 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The observed equilibrium constants (Kobs) of the creatine kinase (EC 2.7.3.2), myokinase (EC 2.7.4.3), glucose-6-phosphatase (EC 3.1.3.9), and fructose-1,6-diphosphatase (EC 3.1.3.11) reactions have been determined at 38 degrees C, pH 7.0, ionic strength 0.25, and varying free magnesium concentrations. The equilibrium constant (KCK) for the creatine kinase reaction defined as: KCK = [sigma ATP] [sigma creatine] divided by ([sigma ADP] [sigma creatine-P] [H+]) was measured at 0.25 ionic strength and 38 degrees C and was shown to vary with free [Mg2+]. The value was found to be 3.78 x 10(8) M-1 at free [Mg2+] = 0 and 1.66 x 10(9) M-1 at free [Mg2+] = 10(-3) M. Therefore, at pH 7.0, the value of Kobs, defined as Kobs = KCK[H+] = [sigma ATP] [sigma creatine] divided by ([sigma ADP] [sigma creatine-P] was 37.8 at free [Mg2+] = 0 and 166 at free [Mg2+] = 10(-3) M. The Kobs value for the myokinase reaction, 2 sigma ADP equilibrium sigma AMP + sigma ATP, was found to vary with free [Mg2+], being 0.391 at free [Mg2+] = 0 and 1.05 at free [Mg2+] = 10(-3) M. Taking the standard state of water to have activity equal to 1, the Kobs of glucose-6-P hydrolysis, sigma glucose-6-P + H2O equilibrium sigma glucose + sigma Pi, was found not to vary with free [Mg2+], being 110 M at both free [Mg2+] = 0 and free [Mg2+] = 10(-3) M. The Kobs of fructose-1,6-P2 hydrolysis, sigma fructose-1,6-P2 equilibrium sigma fructose-6-P + sigma Pi, was found to vary with free [Mg2+], being 272 M at free [Mg2+] = 0 and 174 M at free [Mg2+] = 0.89 x 10(-3) M.
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PMID:Effects of pH and free Mg2+ on the Keq of the creatine kinase reaction and other phosphate hydrolyses and phosphate transfer reactions. 3 98

Some enzymatic activities were studied in long ter cultures of human liver cells : glucose-6-phosphatase, U.D.P. glucuronosyltransferase, phenylalanine 4-hydroxylase and tyrosine aminotransferase. Only weak tyrosine aminotransferase activity has been found in 12 subcultures, and it has not been increased by addition of corticoids. This tyrosine aminotransferase activity has been measured at different passages of the culture. Our results are compared with those found in literature. The different reasons which could explain the absence of liver specific biochemical functions have been discussed.
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PMID:Study of some enzymatic activities in human liver cell cultures. 3 33

alpha-glucosidases are cellular enzymes, able to split the polysaccharides into glucose. In subcellular fractions from rat and trout hepatocytes, the distribution patterns of neutral alpha-glucosidase and of glucose-6-phosphatase appear to be very similar, i.e., closely linked to the endoplasmic reticulum, and are somewhat related to the particular glycogen. The data suggest a probable role of neutral alpha-glucosidase in cell physiology and in carbohydrates metabolism.
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PMID:[Similar distribution of the activities of neutral alpha-glucosidase (gamma-amylase) and glucose-6-phosphatase in subcellular fractions from rat and trout livers]. 3 99

Twelve acid hydrolases, 4 near-neutral hydrolases, and alkaline phosphatase were demonstrated in 0.34 M sucrose homogenates of Trypanosoma cruzi strain Y: p-nitrophenylphosphatase and alpha-naphthylphosphatase, with optimum pH at approximately 6.0; alpha=ga;actpsodase. beta=ga;actpsodase. beta=g;icpsodase, N-acetyl-beta-glucosaminidase, cathepsin A and peptidase I and III, with optimum pH between 5.0 and 6.0; and arylsulfatase, cathepsin D, alpha-arabinase and alpha-mannosidase with optimum pH at approximately 4.0. alpha-Glucosidase, glucose-6-phosphatase and peptidase II had optimum pH at approximately 7.0. beta-Glycerophosphatase had a broad pH-activity curve from 4,0 to 7.4, with maximum activity at pH 7.0. The main kinetic characteristics of these enzymes and their quantitative assay methods were studied. No activity was detected for alpha-fucosidase, beta-xylosidase, beta-glucuronidase, elaidate esterase, acid lipase, and alkaline phosphodiesterase.
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PMID:Acid and neutral hydrolases in Trypanosoma cruzi. Characterization and assay. 4 19

The presence of ATPase activity was demonstrated in isolated nuclei of human spermatozoa by high resolution cytochemical methods. The Wachstein and Meisell technique as modified by Marchesi and Palade was used. ATPase activity was identified as dense and irregularly distributed granules confined to the exposed surface of spermatozoa nuclei. Within the nucleus the reaction product appeared as electron dense precipitates randomly distributed. Control experiments were negative. Deposits of lead phosphate specifically restricted to the exposed surface of nuclei were interpreted as an indication of a glucose-6-phosphatase and/or phosphohydrolase activity. Whether this activity is located in remnants of the inner leaflet of the nuclear envelope is not known. The presence of the enzyme activity within the nucleus is thought to be related to aerobic ATP synthesis previously suggested. If so, this function may be involved in establishing and/or maintaining the highly complex structural organization of spermatozoa nuclei.
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PMID:Distribution of ATPase in isolated human spermatozoa nuclei: a high resolution cytochemical study. 4 Sep 6

Intraperitoneal administration of diazepame and phenazepame into rats /at a dose 50 mg/kg/ within 4 days did not induce liver microsomal enzymes. After administration of chlordiazepoxide at the same dose content of cytochrome P-450 was increased and the rate of dimethylaniline demethylation was elevated. Content of protein as well as NADPH-cytochrome-c-reductase and glucose-6-phosphatase activities were increased after intraperitoneal administration of all the preparations at a dose 100 mg/kg within 4 days. Experiments on the potentiation of hexenal effect demonstrated the decrease in the time of sleep in animals, treated with chlordiazepoxide at a dose 100 mg/kg of body weight.
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PMID:[Effect of 1,4-benzodiazepine tranquilizers on the activity of the hepatocyte hydroxylating complex and glucose-6-phosphatase in white rats]. 4 17

2-Deoxy-D-galactose, in a dose of 3 mmol/kg, was administered intraperitoneally twice daily to young rats for periods up to 12 weeks. This dosage schedule resulted in recurrent phosphate trapping predominantly in liver. UTP deficiency was excluded by simultaneous uridine injections. Phosphate trapping was caused by the rapid accumulation of 2-deoxy-D-galactose 1-phosphate and was most pronounced in liver but also demonstrated in small intestine, brain, spleen, and thymus. The marked, although transient, drop in the hepatic content of inorganic phosphate triggered the catabolism of adenine nucleotides and a loss of ATP. Other metabolic pathways affected by phosphate deficiency include glycogenolysis and glycolysis. Increasing with time, repeated doses of the galactose analog led to retardation and arrest of growth, hepatomegaly, and splenomegaly. The average relative liver and spleen weights were elevated 2.5- and 4.5-fold, respectively, after 12 weeks of treatment. Liver damage was indicated by hyperbilirubinaemia and a progressive rise in the activity in plasma of sorbitol dehydrogenase, alkaline phosphatase, and gamma-glutamyltransferase. Examination by light and electron microscopy showed increasing numbers of vacuoles, surrounded by a single membrane, in hepatocytes, sinusoidal endothelial cells, and Kupffer cells. Focal cytoplasmic degeneration in hepatocytes was occasionally indicated by formation of autophagic vacuoles and finger print lysosomes. Hepatocytes of 2-deoxy-D-galactose-treated rats showed a dissociation and fragmentation of the rough endoplasmic reticulum. Sinusoidal endothelial cells and Kupffer cells were markedly enlarged, the latter contained a PAS-positive but amylase resistant substance. Extrahepatic changes included an increased occurrence of vacuolated cells in thymus. Phosphate trapping and its metabolic consequences are common phenomena in the experimental injury induced b 2-deoxy-D-galactose and in some hereditary diseases such as uridylyltransferase deficiency galactosaemia, fructose intolerance and glucose-6-phosphatase deficiency.
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PMID:Consequences of recurrent phosphate trapping induced by repeated injections of 2-deoxy-D-galactose. Biochemical and morphological studies in rats. 4 10

In experiments with albino rats it was found that after administration of phytobacteriomycin, trichotecin, hygromycin B or levoristatin into the stomach in doses of 1/20 of LD50 activity of the microsomal enzymes of the liver cells significantly changed and the changes persisted within at least 2 weeks. The above antibiotics induced similar changes in the lysosome enzyme, i.e. acid phosphatase, providing an increase in its activity. Changes in the activity of succinate dehydrogenase (mytochondria indicator enzyme), glucose-6-phosphatase (ribosome indicator enzyme) and aspartate aminotransferase (cytoplasm indicator enzyme) were different for each antibiotic. It is concluded that the above antibiotics were capable of impairing on intoxication the enzymatic function of various cell microstructures, though the levels of the change direction may be different.
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PMID:[Effect of phytobacteriomycin, trichotecin, hygromycin B and levoristatin on some rat liver enzymes]. 5 75

Rat liver fixed with dimethylsuberimidate (DMS) was studied to investigate the use of diimidoesters as dixatives for light and electron microscopic cytochemistry. Paraffin sections of liver fixed with DMS at pH 9.5 were weakly stained with the ninhydrin-Schiff procedure, indicating extensive reaction of NH3+ groups with the fixative. Nuclei were strongly strained by the Feulgen procedure, with no background [corrected] reaction. In contrast, glutaraldehyde fixation resulted in a significant background reaction in the cytoplasm and nuclei in controls for the Schiff-based stains. DMS-fixed liver stained intensely for glycogen with the Periodic acid-Schiff procedure, and biochemical analysis of glycogen retention and extractability indicated that DMS retained considerably more glycogen in sections than glutaraldehyde. DMS-fixed liver incubated for thiamine pyrophosphatase activity revealed reaction product in ER cisternae, Goli saccules and bile canaliculi. Peroxisomes were strongly reactive for catalase activity after incubation in diaminobenzidine medium, and reaction product of glucose-6-phosphatase activity was considerably greater following DMS fixation than after glutaraldehyde. Biochemical studies revealed up to twice as musch residual activity of glucose-6-phosphatase after DMS fixation. These results suggest that DMS may be useful as a primary fixative for certain cytochemical procedures.
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PMID:Tissue fixation with diimidoesters as an alternative to aldehydes. II. Cytochemical and biochemical studies of rat liver fixed with dimethylsuberimidate. 6 Dec 39

The effects of fixation with various concentrations of glutaraldehyde or formaldehyde, acetone or ethanol, and freeze-drying on 5 phosphatases of Eimeria tenella and chick kidney cell cultures were demonstrated in situ. Gultaraldehyde inactivated the phosphatases more than did the formaldehyde, but the effect of the combination of the 2 (Karnovsky's fixative) was greater than that of either glutaraldehyde or formaldehyde alone. The higher the concentration of aldehyde and the longer the duration of exposure, the greater the inactivation. The order of sensitivity to aldehyde fixation of the enzymes tested was glucose-6-phosphatase greater than thiamine pyrophosphatase greater than 5'-nucleotidase greater than adenosine triphosphatase greater than acid phosphatase. Cytologic detail was preserved more efficiently with glutaraldehyde than with formaldehyde. Optimal preservation of enzyme activity for cytochemistry was with 2% glutaraldehyde for 30 min or 2% formaldehyde for 1 hr for G-6-Pase, TPPase, and 5'-nucleotidase, and with 2% glutaraldehyde or 2% formaldehyde for 2 hr with ATPase and AcPase. Quenching with subsequent fixation in cold acetone or ethanol resulted in complete inactivation of G-6-Pase, TPPase, and 5'-nucleotidase; although cells fixed in this manner yielded large amounts of reaction product for ATPase and AcPase, the distribution was diffuse, and some of it appeared to be artifactual. Quenching with subsequent freeze-drying was unsatisfactory because nearly all of the cell layers rolled off the cover glasses.
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PMID:Effect of fixation on demonstration of phosphatases of Eimeria tenella grown in chick kidney cell cultures. 6 Dec 71


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