The Fine Structural Localization of Glucose-6-Phosphatase in Rat Liver

Tice, Lois W.; Barrnett, Russell J.

doi:10.1177/10.6.754

Cited by 151 publications

(54 citation statements)

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“…It is therefore possible that NAD from the extracellular medium is entering the cisternae of the endoplasmic reticulum and being degraded by a NADase a t the inside of the membrane facing the cisterna. There is some evidence that another microsomal enzyme, namely glucose-6-phosphatase, is at least partially localized at the inside of the membrane of the endoplasmic tubules [40]. Further experiments will be necessary to attribute the microsomal NADase to a well defined membrane fraction.…”

Section: Discussionmentioning

confidence: 99%

Localization and Regulation of Two NAD Nucleosidases in Ehrlich Ascites Cells

et al. 1968

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After differential centrifugation of Ehrlich ascites cells by the de Duve method, NAD nucleosidase activities were found in the nuclear and the microsomal fractions, but not in the lysosomal fraction.The nuclear NAD nucleosidase is inhibited 500/, by 0.2 mM nicotinamide and is highly specific for /?-NAD. Its activity is markedly decreased after DNase treatment; it is associated with chromatin and is very probably identical with an enzyme that polymerizes the adenosine diphosphate ribose moiety of NAD to an acid-insoluble polymer first described in rat liver nuclei by Chambon, Weill, and Mandel. by 1.2 mM nicotinamide, and splits NAD, NADP and NMN a t a ratio of 1 : 0.5 : 0.2. NAD and NADP nucleosidase activities are reciprocally inhibited by NADP and NAD. Evidence is presented that the microsomal enzyme is active mainly a t the surface of the cell.Nicotinamide concentration may be one factor regulating the nuclear but not the microsomal NAD nucleosidase. Within the cell, NAD is protected by membrane structure from degradation by the microsomal NAD nucleosidase. The microsomal NAD nucleosidase is inhibited 50The activity of NAD nucleosidase (NADase) in homogenates of Ehrlich ascites cells far exceeds the calculated rate of NAD synthesis in intact cells [l]. The rapid decrease in the NAD content of ascites cells after treatment with alkylating agents [2,3] is very probably caused by a release of the intracellular inhibition of NADase [1,4]. The present study was undertaken to elucidate the mechanism(s) protecting NAD from degradation within the cell.

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Section: Discussionmentioning

confidence: 99%

Localization and Regulation of Two NAD Nucleosidases in Ehrlich Ascites Cells

et al. 1968

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“…hepatocytes (1) . In situ cytochemical tests (2,3) At all stages of development studied, the reaction suggest that the inorganic phosphate produced by enzymatic hydrolysis of G6P is released into phatase ; EDTA, ethylenediaminetetraacetate ; Pi, inorganic phosphate ; RNA, ribonucleic acid ; PLP, I Abbreviations used are : ER, endoplasmic reticulum ; phospholipid ; TCA, trichloroacetic acid ; OD, optical G6P, glucose-6-phosphate ; G6Pase, glucose-6-phosdensity .…”

Section: Introductionmentioning

confidence: 99%

Differentiation of Endoplasmic Reticulum in Hepatocytes

Leskes

Siekevitz

Palade

1971

The Journal of Cell Biology

123

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Electron microscope cytochemical localization of glucose-6-phosphatase in the developing hepatocytes of fetal and newborn rats indicates that the enzyme appears simultaneously in all the rough endoplasmic reticulum of a cell, although asynchronously within the hepatocyte population as a whole . To confirm that the pattern of cytochemical deposits reflects the actual distribution of enzyme sites, a method to subfractionate rough endoplasmic reticulum was developed . The procedure is based on the retention of the cytochemical reaction product (precipitated lead phosphate) within freshly prepared rough microsomes reacted in vitro with glucose-6-phosphate and lead ions . Lead phosphate increases the density of the microsomes which have glucose-6-phosphatase activity and thereby makes possible their separation from microsomes lacking the enzyme ; separation is obtained by isopycnic centrifugation on a two-step density gradient . The procedure was applied to rough microsomes isolated from rats at several stages during hepatocyte differentiation and the results obtained agree with those given by cytochemical studies in situ . Before birth, when only some of the cells react positively for glucose-6-phosphatase, only a commensurate proportion of the rough microsome fraction can be rendered dense by the enzyme reaction . At the time of birth and in the adult, when all cells react positively, practically all microsomes acquire deposit and become dense after reaction . Thus, the results of the microsome subfractionation confirm the cytochemical findings ; the enzyme is evenly distributed throughout all the endoplasmic reticulum of a cell and there is no regional differentiation within the rough endoplasmic reticulum with respect to glucose-6-phosphatase . These findings suggest that new components are inserted molecule-by-molecule into a pre-existing structural framework . The membranes are thus mosaics of old and new molecules and do not contain large regions of entirely "new" membrane in which all of the components are newly synthesized or newly assembled .

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“…Glucose-6-phosphatase. Incubation in a medium containing 0.125% glucose-6-phosphate and 2% lead nitrate for 30 min at 37ºC, substituting with cerium chloride (Wachstein and Meisel, 1956;Tice and Barrnett, 1962).…”

Section: Methodsmentioning

confidence: 99%

Three-Dimensional Observations on Thick Biological Specimens by High Voltage Electron Microscopy

Nagata¹

2011

Image Anal Stereol

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Thick biological specimens prepared as whole mount cultured cells or thick sections from embedded tissues were stained with histochemical reactions, such as thiamine pyrophosphatase, glucose-6-phosphatase, cytochrome oxidase, acid phosphatase, DAB reactions and radioautography, to observe 3-D ultrastructures of cell organelles producing stereo-pairs by high voltage electron microscopy at accerelating voltages of 400-1000 kV. The organelles demonstrated were Golgi apparatus, endoplasmic reticulum, mitochondria, lysosomes, peroxisomes, pinocytotic vesicles and incorporations of radioactive compounds. As the results, those cell organelles were observed 3-dimensionally and the relative relationships between these organelles were demonstrated.

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The Fine Structural Localization of Glucose-6-Phosphatase in Rat Liver

Cited by 151 publications

References 0 publications

Localization and Regulation of Two NAD Nucleosidases in Ehrlich Ascites Cells

Localization and Regulation of Two NAD Nucleosidases in Ehrlich Ascites Cells

Differentiation of Endoplasmic Reticulum in Hepatocytes

Three-Dimensional Observations on Thick Biological Specimens by High Voltage Electron Microscopy

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