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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)

Lean and genetically obese (fa/fa) rats were fed ad libitum, or fasted for 17 h and then meal-fed for varying time intervals. During refeeding, glucose-6-phosphatase activity of lean rats declined to the low value that was present in livers of fasted obese rats and which remained unchanged in the obese group during the meal. Refeeding also resulted in increases in hepatic concentrations of glucose-6-phosphate and fructose-6-phosphate, fructose 1,6-bisphosphate, fructose-2,6-bisphosphate, alpha-glycerophosphate, pyruvate and lactate in lean and obese rats, absolute values being higher in the fasted obese than in the fasted lean group. Obese animals had higher postprandial portal blood insulin, glucose and lactate concentrations than lean animals. In spite of this, the rate of hepatic glycogen deposition was the same in both groups and was accompanied by similar glycogen synthase a levels. Following refeeding, phosphorylase was transiently inactivated in livers of lean but not of obese animals, while glycogen synthase was inactivated in both groups. The data suggest that in lean animals refeeding was associated with a stimulation of liver glycolysis, presumably by insulin; in fasted obese rats hepatic glycolysis was already in a stimulated state and was only slightly enhanced further after the meal, in keeping with their unaltered hyperinsulinaemia; there was an increased turnover of liver glycogen or a resistance to insulin stimulation of glycogen synthesis in fa/fa rats during refeeding.
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PMID:The onset of liver glycogen synthesis in fasted-refed lean and genetically obese (fa/fa) rats. 303 11

Aged individuals have diminished resistance to severe sepsis and septic shock. Past work with animals suggested that an important determinant of survival was the ability of the liver to supply glucose. In this study, young adult (3 to 4 months) and old (24 months) Fischer 344 rats were fasted and subjected to cecal incisions producing a rapidly lethal peritonitis. We then determined gluconeogenic intermediates in the liver. In the old rats with peritonitis, hexosemonophosphates (HMP) increased 50% relative to control liver, whereas in the young animals with peritonitis, the substrate decreased 50%. The accumulation of HMP in the old rat liver cells indicates a failure to dephosphorylate glucose-6-phosphate (G6P). This increase in HMP is associated with a decline in hepatic glucose-6-phosphatase (G6Pase), the final enzyme in the gluconeogenic pathway, and is reflected in a significant reduction in serum glucose in old Fischer 344 rats when compared to young Fischer rats.
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PMID:Effect of aging on hepatic carbohydrate metabolism in septic rats. 304 Aug 52

In type 1 glycogen storage diseases, glucose-6-phosphatase may be present but associated with impaired transport of glucose-6-phosphate (type 1b) or inorganic phosphate (type 1c) through microsomal membranes. The type 1c is very rare (2 published cases). The more frequent type 1b presents all the clinical manifestations of type 1a and specific signs: recurrent stomatitis, frequent infections, chronic inflammatory bowel disease secondary to neutropenia and neutrophil dysfunction. Glucose-6-phosphatase activity is low when measured on fresh liver tissue, but is restored after detergent treatment. A good metabolic control does not influence neutropenia and its consequences.
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PMID:[Glycogenoses type 1b and 1c]. 306 19

Treatment with malathion resulted in an increase in the level of blood glucose and lactate and reduced cerebral glycogen, 2 hr after its administration. The blood pyruvate level was not changed. The activities of glycogenolytic enzymes (glycogen phosphorylase and phosphoglucomutase) were increased significantly in the brain, whereas that of glucose-6-phosphatase remained unchanged. The activity of the glycolytic enzyme-hexokinase was increased significantly in malathion-treated animals, whereas those of the glucose-6-phosphate and lactate dehydrogenases were not significantly changed. The changes in enzyme activities may be a compensatory mechanism to provide energy in the form of glucose to cerebral tissue on account of stimulatory effects in malathion-treated animals.
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PMID:Cerebral glycogenolysis and glycolysis in malathion-treated hyperglycaemic animals. 357 75

Clinical, hematologic, and immunologic findings were reviewed in 21 patients with glycogenosis Ib. Fifteen of the patients suffered from moderate to severe bacterial infections. Ten patients had excessive epistaxis or bleeding from surgical sites, and eight suffered oral and anal mucosal ulceration. Sixteen of 21 patients exhibited chronic neutropenia associated with abnormalities in myeloid maturation and decreases in the bone marrow storage and peripheral marginating pools. Diminished neutrophil motility was documented in 14 of 15 patients tested, and adherence was decreased in three patients studied. Neutrophil microbicidal activity, reduction of nitroblue tetrazolium, and ingestion were normal in all patients tested. Bleeding times were prolonged in five of eight patients, and results of platelet function studies were abnormal in five individuals. Excessive bleeding in patients with glycogenoses Ia and Ib are similar and may be secondary to the functional deficiency of glucose-6-phosphatase. However, neutropenia, neutrophil dysfunction, and the resulting infectious complications are specific for Ib disease and may be related to abnormal glucose-6-phosphate transport.
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PMID:Infectious and bleeding complications in patients with glycogenosis Ib. 386

Promastigotes of Leishmania mexicana amazonensis possess an elaborated system of cytoplasmic membranes which is clearly visualized when the cells are fixed in a glutaraldehyde solution containing Ca++ and post-fixed in an osmium tetroxide solution containing Ca++ and potassium ferricyanide. When the parasites are incubated in a medium containing glucose-6-phosphate and lead nitrate, reaction product indicative of glucose-6-phosphatase activity is seen in the membrane system confirming that it corresponds to the endoplasmic reticulum (ER). A large concentration of profiles of the ER was observed at the anterior region of the cell, close to the flagellar pocket, appearing as a 'proliferative focus'. Profiles of the ER radiate toward the periphery of the cell penetrating between the subpellicular microtubules and reaching the plasma membrane.
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PMID:Fine structure and cytochemistry of the endoplasmic reticulum and its association with the plasma membrane of Leishmania mexicana amazonensis. 402 Sep 25

Enzyme histochemical methods were performed on sporozoite infected liver tissue of rats in order to gain insight into the nutrition and metabolism of exoerythrocytic forms of Plasmodium berghei. The following enzymes were demonstrated in the hepatocytic stages of the parasites, obtained 41 and 48 h after inoculation of sporozoites: acid phosphatase, cytochrome oxidase, NADH-tetrazolium reductase, succinate dehydrogenase, NAD+ and NADP+ dependent isocitrate dehydrogenase, NADP+-dependent malate dehydrogenase, lactate dehydrogenases, 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenases and alpha-glycerol-phosphate dehydrogenase. The results suggest that a conventional Embden-Meyerhoff pathway, pentose phosphate pathway and Krebs' citric acid cycle may in part be present in these exoerythrocytic parasites. Alkaline phosphatase, nucleoside polyphosphatase, 5' nucleotidase, glucose-6-phosphatase, alpha-glucan phosphorylase, NAD+ dependent malate dehydrogenase, amino-peptidase M and non-specific esterases were not detected by our techniques in the parasite. The enzyme distribution of this intrahepatocytic malaria parasite revealed by histochemistry is compared with the enzyme distribution in the other phases of the parasite's life cycle.
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PMID:Histochemical observations on the exoerythrocytic malaria parasite Plasmodium berghei in rat liver. 608 94

The effects of temperature and pH on the phosphohydrolase activity of carp hepatic glucose-6-phosphatase (EC 3.1.3.9) have been investigated. The enzyme activity was maximum at about 308 K and in the pH range 5-6.5. The apparent Michaelis constant (KM) and Vmax of the reaction with glucose-6-phosphate were found to be 14.8 mM and 2.27 nmol/min/mg protein. The enzyme activity was partly inhibited by EDTA, while in the presence of sufficient PCMB virtually total inhibition was observed.
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PMID:Studies on the properties of glucose-6-phosphatase from carp liver microsomes (Cyprinus carpio L.). 608 28

The endoplasmic reticulum (ER) and glycogen in secretory cells of anterior pituitary glands from control and fasted mice were investigated ultrastructurally using cytochemical staining techniques. Potential enzyme cytochemical markers for the ER included glucose-6-phosphatase (G6Pase) and nucleoside diphosphatase (NDPase) activities. Presumptive glycogen particles were identified in tissue postfixed in 1% osmium tetroxide-1.5% potassium ferrocyanide or in ultrathin sections poststained with periodic acid-thiocarbohydrazide-silver proteinate. The ER appeared to be related structurally and cytochemically to the nuclear envelope and cis Golgi saccules. Similar relationships between the ER and the trans Golgi saccules or GERL were not observed. In anterior pituitary glands from control mice, G6Pase activity was prominent within the lumen of the ER, nuclear envelope, and cis Golgi saccules of all cells; reaction product was absent in the trans Golgi saccules and in GERL. G6Pase activity was sparse to non-existent in anterior pituitary cells from fasted mice. The cytochemical reaction utilizing the Gomori lead capture method indicated that G6Pase in anterior pituitary cells may function as a phosphohydrolase for converting glucose-6-phosphate to glucose. Cytochemical localization of NDPase activity was not evident in the ER; reaction product was localized consistently in one or two trans Golgi saccules and occasionally in GERL and nascent secretory granules. Presumptive glycogen particles in each of the different secretory cell types from control mice appeared as 20-30 nm wide, electron-dense particles scattered as single entities throughout the cytoplasm. Anterior pituitary glands from fasted mice exhibited conspicuous and numerous clumps of glycogen particles in addition to scattered particles in all cell types except corticotrophs, which appeared to be devoid of glycogen. Glycogen particles were absent in anterior pituitary cells incubated in a medium containing diastase. Our results suggest that in anterior pituitary cells of the mouse: 1) the phosphohydrolytic activity of G6Pase is a reliable cytochemical marker for the ER; 2) the ER is associated morphologically and cytochemically with the cis face but not with the trans face of the Golgi apparatus or with GERL; 3) some glucose-6-phosphate, a possible substrate for G6Pase in vivo, may be derived indirectly from glycogen stores; and 4) modulations in G6Pase activity and glycogen storage during fasting may reflect an alteration in energy metabolism.
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PMID:Cytochemical staining of the endoplasmic reticulum and glycogen in mouse anterior pituitary cells. 609 57

Patients with glycogen storage disease (GSD) type 1b have shown normal activity of glucose-6-phosphatase (EC 3.1.3.9) as assayed in frozen liver, though their clinical and biochemical findings were similar to those of patients with GSD 1a (McKusick 23220) (Senior and Loridan, 1968). In 1978, we suggested that a basic defect of GSD 1b exists in the glucose-6-phosphate (G6P) transport system (Narisawa et al., 1978; Igarashi et al., 1979). Since then, there have been reports confirming our observation (Beaudet et al., 1980; Lange et al., 1980; Corbeel et al., 1981; Schaub et al., 1981). Recently, it was postulated that the G6Pase system contains a phosphate translocase which mediates the efflux of phosphate, in addition to a G6P translocase and a non-specific phosphohydrolase (Arion et al., 1980). Therefore, it is possible that GSD 1b is caused by a defect of phosphate translocase. In this paper, the basic defect in GSD type 1b was investigated in two patients; one with severe, the other with mild, clinical symptoms.
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PMID:Glycogen storage disease type 1b due to a defect of glucose-6-phosphate translocase. 613 35


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