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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)

Glucose-6-phosphatase (glucose-6-phosphohydrolase and its associated phosphotransferase activities) was determined in brain tissue and in several preparations derived from brain tissue. These included purified capillaries and established cell lines of neuronal or glial origin. Since it has been suggested that glucose-6-phosphatase may be involved in sugar transport, the characteristics of that process were examined in these preparations. The pattern of uptake of 2-deoxy-D-glucose in four cell lines was shown to involve transport of the analog across the cell membrane that was more rapid than the subsequent phosphorylation of the sugar in the intracellular compartment. In the remaining cell lines and in purified capillaries, phosphorylation of 2-deoxy-D-glucose was at least as rapid as uptake. No differences could be found between the cells in these two categories with respect to amount or localization of glucose-6-phosphatase, ability to phosphorylate 3-O-methyl-D-glucose, or ability to phosphorylate extracellular and intracellular 2-deoxy-D-glucose. In the course of these experiments, it was found that there was a rapid efflux of 2-deoxy-D-glucose from cells that had taken up this sugar. The efflux involves a dephosphorylation step catalyzed by intracellular phosphatase that releases free sugar in the cytoplasm. Glucose-6-phosphatase thus probably has no major role in the phosphorylation of glucose in brain cells, but acts in the more conventional sense, i.e. as a phosphohydrolase.
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PMID:Cerebral glucose-6-phosphatase and the movement of 2-deoxy-D-glucose across cell membranes. 2 Apr 41

The in vitro effects of vitamin D3 metabolites, parathyroid extract (PTE), purified parathyroid hormone (bPTH), vitamin A, and heparin on acid and alkaline phosphatases in rat or mouse calvaria in culture were investigated. Results show that: (a) when compared to values found in half calvaria incubated for 24 h in control medium, the bone acid and alkaline phosphatase content is significantly higher in paired halves incubated with PTE (L USP/ml), bPTH (4 x 10(-8)M), heparin (5 USP/ml), vitamin A (23 USP/ml), 25-(OH)D3 (2.5 x 10(-11) to 2.5 x 10(-8)M), 24,25-(OH)2D3, and 1,25-(OH)2D3 (2.5 x 10(-12) to 2.5 x 10(-7M); (b) the presence of 24,25-(OH)2D3 at low concentrations in the incubation medium decreases significantly the PTE, bPTH, vitamin A, or heparin induced stimulation of the phosphatase activities. This interaction is also observed when measuring beta glucuronidase and glucose-6-phosphatase activities and 45Ca release from previously labeled mouse calvaria; (c) a similar activity could not be found with 1,25-(OH)2D3 suggesting that 24,25-(OH)2D3 may have a specific role in bone metabolism.
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PMID:Interaction of 24,25-dihydroxyvitamin D3 and parathyroid hormone on bone enzymes in vitro. 11 87

Carbamyl phosphate : glucose phosphotransferase and glucose-6-phosphate (Glc-6-P) phosphohydrolase activities have beeh demonstrated in pancreas, adrenals, brain, testes, spleen, and lung. Catalysis of these activities by classical multifunctional glucose-6-phosphatase (D-glucose-6-phosphate phosphohydrolase; EC 3.1.3.9) has been firmly established for the first four of these tissues on the basis of characteristic catalytic properties of the transferase pH-activity profiles, apparent Km values for carbamyl phosphate and glucose, substrate specificity, susceptibility to inhibition by molybdate, and activation by deoxycholate. Additional such activity due to non-specific acid (and alkaline) phosphatase action also is indicated at very high glucose concentrations. The possible physiological significance of the newly-elucidated presence of glucose-6-phosphatase-phosphotransferase in these various tissues, in addition to previously extensively studied liver, kidney, and mucosa of small intestine, is discussed briefly.
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PMID:Mammalian carbamyl phosphate : glucose phosphotransferase and glucose-6-phosphate phosphohydrolase: extended tissue distribution. 16 20

1. Pure or impure C-type phospholipases hydrolysed rat liver microsomal phosphatides in situ at 5 degrees or 37 degrees C. At 5 degrees C mean hydrolysis of total phospholipids was 90% by Bacillus cereus and 75% by Clostridium perfringens (Clostridium welchii) C-type phospholipases. 2. Four degrees of inhibition of glucose 6-phosphatase (D-glucose 6-phosphate phosphohydrolase; EC 3.1.3.9) resulted. (a) At 37 degrees C inhibition was virtually complete and apparently irreversible. (b) At 5 degrees C phospholipase C inhibited 50-87% of the activity expressed by intact control microsomal fractions. (c) Bovine serum albumin present during delipidation alleviated most of this inhibition: at 5 degrees C phospholipase C plus bovine serum albumin inhibited by 0-35% (mean 18%):simultaneous stimulation by the destruction of its latency seems to offset glucose 6-phosphatase inhibition, sometimes completely. (d) If latency was first destroyed, phospholipase C plus bovine serum albumin inhibited 30-50% of total glucose 6-phosphatase activity at 5 degrees C. Only this inhibition is likely largely to reflect the lower availability of phospholipids, essential for maximal enzyme activity, as it is virtually completely reversed by added phospholipid dispersions. Co-dispersions of phosphatidylserine plus phosphatidylcholine (1:1, w/w) were especially effective but Triton X-100 was unable effectively to restore activity. 3. Considerable glucose 6-phosphatase activity survived 240min of treatment with phospholipase C at 5 degrees C, but in the absence of substrate or at physiological glucose 6-phosphate concentrations the delipidated enzyme was completely inactivated within 10min at 37 degrees C. However, 80mM-glucose 6-phosphate stabilized it and phospholipid dispersions substantially restored thermal stability. 4. It is concluded that glucose 6-phosphatase is at least partly phospholipid-dependent, and complete dependence is not excluded. For reasons discussed it is impossible yet to be certain which phospholipid class(es) the enzyme requires for activity.
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PMID:Inhibition of glucose 6-phosphatase by pure and impure C-type phospholipases. Reactivation by phospholipid dispersions and protection by serum albumin. 16 86

Electron microscopic cytochemistry was used to determine the localization of five phosphatase enzymes-glucose-6-phosphatase, inosine diphosphatase, thiamine pyrophosphatase, acid phosphatase, and adenosine triphosphatase-in control human testes. Glucose-6-phosphatase occurred in the endoplasmic reticulum and nuclear envelope of Sertoli cells, Leydig cells and primitive spermatogonia, but was not observed in more advanced spermatogenic cells. The presence of glucose-6-phosphatase activity paralleled the presence of glycogen in spermatogenic cells, i.e., both occurred in type AL and AD spermatogonia but not in type AP or B spermatogonia or in more advanced spermatogenic cells. Inosine diphosphatase activity was found in the endoplasmic reticulum, nuclear envelope, and Golgi complex of Sertoli cells and all spermatogenic cells except late spermatids. Additionally, inosine diphosphatase activity was localized at the junctions between Sertoli cells and late spermatids, but was not associated with any other plasma membrane. Thiamine pyrophosphatase reaction product was found in the Golgi bodies of Sertoli cells and in spermatogenic cells through immature spermatids. Neither inosine diphosphatase nor thiamine pyrophosphatase was observed in the Golgi bodies of spermatids during acrosomal formation. Acid phosphatase activity was found in lysosomes of spermatogonia, spermatocytes, and spermatids, in lysosomes of Leydig cells, and in lysosomes, lipofuscin bodies, and Golgi cisternae of Sertoli cells. It is thought that Sertoli lysosomes play a role in the phagocytosis of degenerating germ cells; however, the role of spermatogenic or Leydig lysosomes is unknown. Adenosine triphosphatase activity occurred at the interfaces between two spermatogonia, and between Sertoli cells and spermatogonia, but was not observed in the spaces between two Sertoli cells, two spermatocytes, two spermatids, or between Sertoli cells and spermatocytes, or between Sertoli cells and spermatids.
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PMID:The fine structural localization of testicular phosphatases in man: the control testis. 17 58

Histochemical localization of various phosphatases, alkaline phosphatase, acid phosphatase, adenosine-tri-phosphatase and glucose-6-phosphatase, have been carried out in the male sex accessory glands of Suncus murinus sindensis, ANDERSON. The seminal vesicle and the COWPER'S gland in Suncus display strong phosphatases activities in the epithelium, except the alkaline phosphatase in the in the COWPER'S gland which is more pronounced in the stroma. The possible role of these phosphatases in the secretory activities of the organ where they are localized have been discussed. In the prostate gland, no phosphatase activity could be revealed in the epithelium and the secretions.
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PMID:Localization of certain phosphatases in the male sex accessory glands of Suncus murinus sindensis, Anderson, the common shrew. 18

The character of the sugar curves, blood insulin activity and the activity of glucose-6-phosphatase was studied in patients with thyrotoxicosis. It was revealed that thyrotoxicosis was accompanied by an increase in Bodwen's hyperglycemic coefficient with the normal values of Rafalsky's and Sokolnikov's coefficients. In this disease blood insulin activity was elevated, and the response of the insular apparatus to hyperglycemia considerably exceeded such in the control. The blood serum activity of glucoso-6-phosphatase was also elevated and failed to change in different glycemia levels. The mentioned indices increased considerably with the aggravation of the disease.
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PMID:[Certain indicators of carbohydrate metabolism and functional state of the islands of Langerhans in thyrotoxicosis]. 19 Jun 3

The activities of hexokinase, glucokinase, phosphofructokinase, glucose-6-phosphate dehydrogenase, glucose-6-phosphatase, and fructose-1,6-diphosphatase were determined in loach embryos developed in solutions of insulin, hydrocortisone, estrone and thyroxin at different stages of embryogenesis. Glucokinase and fructose-1,6-diphosphatase activties are shown not to change markedly under the influence of the above-mentioned hormones. During some periods of early development the hexokinase activity is inhibited by insulin, estrone and thyroxin. The glucose-6-phosphate dehydrogenase activity is suppressed by each of the used hormones at all the stages of early embryogenesis while the glocose-6-phosphatase activity decreased only under the influence of insulin at the cleavage, blastula and gastrula stages. Insulin increased the activity of phosphofructokinase at the cleavage, blastula and early gastrula stages and hydrocortisone, estrone and thyroxine during certain periods of these stages. From middle gastrula two last hormones decreased the phosphofructokinase activity in the loach embryos.
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PMID:[Activity of carbohydrate metabolism enzymes in loach embryos under the influence of hormones]. 19 80

The intracellular location of a variety of enzymes was studied in Amoeba proteus with the use of electron microscopic cytochemical methods, in an attempt to assess the relationships between different membranous organelles. One group of enzymes, including nucleoside diphosphatases (IDPase, UDPase, GDPase, ADPase), carbamoyl phosphatase, alkaline phosphatase, and BAXD oxidase was localized mainly in the rough endoplasmic reticulum, nuclear envelope, and convex side of the Golgi apparatus. Esterase activity had a similar localization except that the Golgi apparatus was "stained" throughout most of its extent. A second group of enzymes was found in Golgi cisternae and vesicles, and in come vacuoles. This group included acid phosphatase, thiamine pyrophosphatase, and aryl sulfatase. Some enzymes previously detected in cytoplasmic membranes of other cells, including glucose-6-phosphatase, showed little or no activity in amoebae. The results suggest that there are chemical similarities and probable functional relationships between the rough endoplasmic reticulum, the nuclear envelope, and the convex side of the Golgi apparatus. On the other hand, the concave pole of the Golgi apparatus, aggregates of smooth tubules and vesicles, and the cell surface appear more closely related to one another than to the endoplasmic reticulum and the convex side of the Golgi apparatus. The cytochemical similarity between the Golgi apparatus and certain vacuoles such as food vacuoles may reflect the role of the Golgi apparatus in the formation of lysosomes. The locations of reaction products of the various enzymes in amoebae are compared with observations reported for other cell types.
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PMID:Relationships between membranous organelles in amoebae studied by electron microscopic cytochemical staining. 19 99

The ultrastructural distribution of glucose-6-phosphatase activity has been investigated in the salamander and frog pancreas. In the pancreas of salamander the enzyme was located in the A-cells, while in frog it occurred in all main types of islet cells B-, A-, and D-cells). As a rule, the reaction intensity was higher in the frog islet cells. No reaction was recorded in the exocrine pancreatic tissue of both species. The glucose-6-phosphatase activity was constantly detected in the lumen of rough endoplasmic reticulum and between the nuclear envelopes. Other enzyme localizations, observed especially in the A-cells of the salamander pancreas, were considered possible diffusion artifacts ro remnants of other phosphatase activity. The enzyme distribution in different types of islet cells, as well as its functional significance are discussed in relation to the findings of other authors.
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PMID:Fine structural localization of glucose-6-phosphatase activity in the pancreatic islets of two amphibian species (Salamandra salamandra L. and Rana esculenta L.). 20 Nov 37


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