Gene/Protein Disease Symptom Drug Enzyme Compound
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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)

An insoluble phosphoprotein of rat brain acquires radioactivity from inorganic phosphate more rapidly during sleep than during wakefulness. It was purified in two ways. The first was solvent delipidation of brain tissue followed by preparative sodium dodecyl sulfate polyacrylamide gel electrophoresis. The second was sucrose gradient centrifugation of a brain homogenate to remove myelin, and gel filtration on Sephadex G-100 and adsorption chromatography on DEAE-Sephadex in the presence of sodium deoxycholate. The products were homogeneous within the limits of the analytical methods used. The apparent molecular weight of the phosphoprotein was 28,000 on sodium dodecyl sulfate polyacrylamide gels, but was much higher in the presence of sodium deoxycholate. The protein had a high content of aspartic and glutamic acids compared to basic amino acids. Analysis of a base hydrolysate, as well as studies of the kinetics of hydrolysis, showed that the radioactive phosphorus was attached to histidine. The NH2-terminal residue was identified as isoleucine. The phosphoprotein purified by the second method was enzymatically active. When it was incubated in vitro with a 32P-labeled supernatant fraction from rat brain (and later with glucose [6-32P]phosphate), a radioactive phosphorylated protein intermediate was formed. Exploration of the several enzymatic activities of the preparation indicated close correspondence to those reported for the glucose-6-phosphatases of liver and kidney. Glucose-6-phosphatase activity was found in all parts of the brain in the membranous subcellular fractions of neurons. It was shown to be co-purified with the sleep-related phosphoprotein. This report constitutes, we believe, the first complete purification of glucose-6-phosphatase from any tissue and an instance in which a change in the state of a cerebral enzyme has been linked to a normal change in the physiological state of the brain.
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PMID:Purification of cerebral glucose-6-phosphatase. An enzyme involved in sleep. 16 41

The activity of hexokinase, glucose-6-phosphatase and glucose-6-phosphoric dehydrogenase was studied in the liver of rats after one hour, one and five days after a single oral administration of organic phosphorus insecticide valekson. It was determined that administration of the preparation led to an increase of activity in the homogenate and solubilization of glucose-6-phosphatase, activation of glucose-6-phosphoric dehydrogenase and inhibition of hexokinase. The changes were maximum one hour after the administration of the compound. The results show that a decrease of the intensity of glucose-6-phosphate formation and metabolism is one of the pathogenetic factors in the development of valekson-induced intoxication.
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PMID:[Activity of glucose-6-phosphate metabolism enzymes in the livers of rats with experimental valekson poisoning]. 20 53

Mechanisms regulating the energy-dependent calcium sequestering activity of liver microsomes were studied. The possibility for a physiologic mechanism capable of entrapping the transported Ca2+ was investigated. It was found that the addition of glucose 6-phosphate to the incubation system for MgATP-dependent microsomal calcium transport results in a marked stimulation of Ca2+ uptake. The uptake at 30 min is about 50% of that obtained with oxalate when the incubation is carried out at pH 6.8, which is the pH optimum for oxalate-stimulated calcium uptake. However, at physiological pH values (7.2-7.4), the glucose 6-phosphate-stimulated calcium uptake is maximal and equals that obtained with oxalate at pH 6.8. The Vmax of the glucose 6-phosphate-stimulated transport is 22.3 nmol of calcium/mg protein per min. The apparent Km for calcium calculated from total calcium concentrations is 31.9 microM. After the incubation of the system for MgATP-dependent microsomal calcium transport in the presence of glucose 6-phosphate, inorganic phosphorus and calcium are found in equal concentrations, on a molar base, in the recovered microsomal fraction. In the system for the glucose 6-phosphate-stimulated calcium uptake, glucose 6-phosphate is actively hydrolyzed by the glucose-6-phosphatase activity of liver microsomes. The latter activity is not influenced by concomitant calcium uptake. Calcium uptake is maximal when the concentration of glucose 6-phosphate in the system is 1-3 mM, which is much lower than that necessary to saturate glucose-6-phosphatase. These results are interpreted in the light of a possible cooperative activity between the energy-dependent calcium pump of liver microsomes and the glucose-6-phosphatase multicomponent system. The physiological implications of such a cooperation are discussed.
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PMID:Calcium sequestration activity in rat liver microsomes. Evidence for a cooperation of calcium transport with glucose-6-phosphatase. 298 15

Based on cytochemical analysis, the enzyme NADP phosphatase is most concentrated in the so-called intercalary cisternae from the mid-region of the Golgi apparatus stack. Using free-flow electrophoresis to separate different Golgi regions of rat liver Golgi apparatus, the NADP phosphatase activity, based on estimation of the rate of release of inorganic phosphate from NADP under standard conditions, was similarly localized to membrane fractions from the center of electrophoretic separations. Peak specific activities for both a putative cis marker (NADH-cytochrome c reductase) and an established trans marker (galactosyltransferase) coincided with minima in NADP phosphatase activity, in agreement with the cytochemical observations. The pattern of distribution of enzyme activity for NADP phosphatase differed from that of both acid phosphatase and glucose-6-phosphatase. The pH optimum was 5.0, the Km for NADP was 0.6 mM and a corresponding production of NAD and inorganic phosphorus was shown. Taken together with other markers for free-flow electrophoresis separation, the NADP phosphatase will provide considerable utility as a specific marker to help identify intercalary cisternae of the mammalian Golgi apparatus and to monitor electrophoretic separations.
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PMID:NADP phosphatase as a marker in free-flow electrophoretic separations for cisternae of the Golgi apparatus midregion. 300 95

Hematological, biochemical, histoenzymological, and histopathological changes in serum and tissues were studied in chickens during outbreaks of nephritis. Hematological studies revealed normocytic-normochromic anemia characterized by increased total erythrocyte counts, hemoglobin, packed cell volume, and erythrocyte sedimentation rate. Albumin-to-globulin ratio and sodium levels in serum, glucose in blood, and alkaline phosphatase and glucose-6-phosphatase in liver and kidneys were decreased. Glutamate pyruvate transaminase, uric acid, non-protein-nitrogen, and potassium levels in serum were increased. No significant change in the calcium, phosphorus, and total protein levels in serum was observed. These changes were directly related to the severity of the nephritis.
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PMID:Clinicopathological, hematological, and biochemical studies in some outbreaks of nephritis in poultry. 407 33

Hereditary fructose intolerance (HFI) is a potentially life-threatening disorder and can be suspected from a detailed nutritional history. The usefulness of 2 diagnostic procedures, fructose tolerance test (FTT) and aldolase assay on biopsied liver, was studied. A standardized intravenous FTT with 200 mg/kg b.w. was done on 11 children with HFI, 17 age-matched contrast children, 6 adults with HFI and 6 adult controls. Blood glucose, phosphorus, urate, magnesium and fructose were followed for 2 hours. By the FTT, each HFI individual was reliably distinguished from controls and contrasts and even from those with acute liver disease other than HFI. Both children with non-HFI hepatopathy examined by both procedures had a normal FTT in spite of reduced liver fructaldolase activity. HFI children responded to the FTT by earlier and more pronounced hypoglycemia than adults, and one girl converted to an adult type response between the ages 12 and 181/2 years. Responses of two HFI sibling pairs and of one set of monozygotic twins were typical for age, but resemblance was no greater than within the unrelated HFI probands. The intravenous FTT is judged a reliable diagnostic tool, simple and harmless if done in hospital. Essential fructosuria is readily diagnosed by the FTT, but fructose-1,6-diphosphatase deficiency and HFI are not differentiated with certainty. Liver biopsies were obtained from 35 children with HFI, 14 contrast persons and 10 controls (of which 9 organ donors) and examined enzymatically. Deficiency of fructaldolase was observed in all HFI children but also in some contrast children suffering from acute liver disease other than HFI. In these, HFI could only be excluded when the reduced activity of reference enzymes such as fructose-1,6-diphosphatase and glucose-6-phosphatase and liver histology were included in the evaluation. In one deceased HFI infant, fructaldolase was deficient in both, liver and kidney cortex. Extent of antibody activation and of heat inactivation of residual fructaldolase varied between unrelated HFI patients but not within families. These results did not contribute to diagnosis but further documented genetic heterogeneity of HFI. For diagnosis of HFI we recommend 1. immediate elimination of fructose from the diet, 2. the intravenous FTT after several weeks of fructose withdrawal, and 3., should diagnosis still be uncertain, laparoscopic liver biopsy for assay of fructaldose and of reference enzymes and for histology.
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PMID:The diagnosis of hereditary fructose intolerance. 626 73

In galactosemia, galactose-1-phosphate (gal-1-P) is not properly metabolized and accumulates in the fetus and after birth in various tissues when lactose or galactose is ingested. Well-treated galactosemics retain a low level of red cell gal-1-P which increases after breaks of diet. The ester is an indicator of the biogenesis of galactose from glucose and has been considered a pathogenic agent by inhibiting enzymes such as glucose-6-phosphatase, glucose-6-phosphate dehydrogenase, phosphoglucomutase, and glycogen phosphorylase, but the evidence remains presumptive. A futile cycle of galactose phosphorylation and dephosphorylation, and the sequestration of phosphorus in gal-1-P are also suspected to play a role in the pathogenesis of galactosemia.
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PMID:Galactose-1-phosphate in the pathophysiology of galactosemia. 767 64

This study was designed to investigate the effects of three diets with different levels of trans fatty acids and the physiologic status on the physicochemical properties and enzymatic activities of liver microsomes and mitochondria. Three groups of 10 female weaning rats each were fed for 10 wk one of three diets differing in their trans fatty acid contents (Control, 0 mol/100 mol total fatty acids; high, 14.5 mol/100 mol; very high, 30 mol/100 mol). At the onset of adult life (10 wk of age), they were mated. Six rats in each group were killed at the end of gestation (Pregnant rat groups). The four remaining pregnant rats continued to receive their experimental diets until weaning of their litters. Six pups from the litters for each group (3 males and 3 females) were selected and fed the same experimental diet as the dams from wk 3 to 10 of age (2nd generation virgin groups) and then killed. Trans fatty acid levels in liver microsomes and mitochondria rose in parallel with the dietary trans fatty acid content, whereas saturated fatty acids dropped in both organelles with increasing trans fatty acids. Pregnant and 2nd generation adult rats fed trans isomers also had lower levels of cholesterol and a lower cholesterol/phosphorus ratio in their liver microsomes compared with controls. A significant interaction between diet and pregnancy was detected in the activities of delta6-desaturase and glucose-6-phosphatase in liver microsomes. Dietary trans fatty acids decreased the activities of both enzymes but only in pregnant rats. No differences in the fluorescence anisotropy of membranes or the enzymatic activities in liver mitochondria were observed. In conclusion, dietary trans fatty acids significantly lowered cholesterol and the cholesterol/phosphorus ratio in liver microsomes. This effect might contribute to low delta6-desaturase and glucose-6-phosphatase activities in liver microsomes of pregnant rats.
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PMID:Dietary trans fatty acids alter the compositions of microsomes and mitochondria and the activities of microsome delta6-fatty acid desaturase and glucose-6-phosphatase in livers of pregnant rats. 1288 31

The hydrogenosome, an organelle that produces molecular hydrogen and ATP from the oxidation of pyruvate or malate under anaerobic conditions, presents some characteristics common to mitochondria. The hydrogenosome of Tritrichomonas foetus, a cattle parasite, is a spherical organelle that presents a peripheral vesicle the origin and behavior of which is poorly known. In this article it is reported an ultrastructural and microanalytical study using energy dispersive X-ray analysis, 3D reconstruction and cytochemistry of the hydrogenosome peripheral vesicle and then compare the results with the endoplasmic reticulum and the nuclear envelope of T. foetus. Similarities between the hydrogenosome peripheral vesicle and the ER are presented. This study included: (1) the detection of ER enzymes by cytochemistry, such as glucose-6-phosphatase, IDPase, acid phosphatase and Ca(2+) -ATPase; (2) elemental composition by X-ray microanalysis and the mapping of calcium, phosphorus and oxygen in both ER and hydrogenosome peripheral vesicle; (3) freeze-fracture; (4) TEM of routine and cryofixed cells by high-pressure freezing and freeze-substitution; (5) 3D reconstruction, (6) monoclonal antibody anti-trichomonads ER; and (6) other cytochemical techniques that detects ER, such as the ZIO and lectins. We found a similar composition of the tested enzymes and other elements present in the ER when compared with the hydrogenosome's peripheral vesicle. It was concluded that, like mitochondria, hydrogenosome presents relationships with the ER, especially the peripheral vesicle.
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PMID:The hydrogenosome peripheral vesicle: similarities with the endoplasmic reticulum. 1803 80

The crystal structure of the apo form of vanadium chloroperoxidase from Curvularia inaequalis reacted with para-nitrophenylphosphate was determined at a resolution of 1.5 A. The aim of this study was to solve structural details of the dephosphorylation reaction catalyzed by this enzyme. Since the chloroperoxidase is functionally and evolutionary related to several acid phosphatases including human glucose-6-phosphatase and a group of membrane-bound lipid phosphatases, the structure sheds light on the details of the dephosphorylation catalyzed by these enzymes as well. The trapped intermediate found is bound to the active site as a metaphosphate anion PO3-, with its phosphorus atom covalently attached to the Nepsilon2 atom of His496. An apical water molecule is within hydrogen-bonding distance to the phosphorus atom of the metaphosphate, and it is in a perfect position for a nucleophilic attack on the metaphosphate-histidine intermediate to form the inorganic phosphate. This is, to our knowledge, the first structural characterization of a real reaction intermediate of the inorganic phosphate group release in a dephosphorylation reaction.
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PMID:Crystal structure of a trapped phosphate intermediate in vanadium apochloroperoxidase catalyzing a dephosphorylation reaction. 1816 51


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