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)

The synaptic complexes of the rat pinealocytes are neither cholinergic nor adrenergic. In the synaptic vesicles, a neurotransmitter carrier substance of lipid nature reacting with OsO4-Zn I2 mixture (similar to that present in both cholinergic and adrenergic vesicles) was not found. In addition, there were no indications of glucose-6-phosphatase or thiamine-pyrophosphatase activity in the synaptic vesicles. Thus, it appears that the synaptic vesicles do not originate from the rough or smooth endoplasmic reticulum. The synaptic ribbons do not contain carbohydrates, are of protein nature and possess some chemical resemblance to microtubules and microtubular bouquets. Appropriate ultracytochemical reactions have not shown detectable quantities of sodium and calcium ions in pinealocyte synaptic complexes.
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PMID:Ultracytochemistry of the synaptic ribbons in the rat pineal organ. 0 83

The peroxisomal core from the liver of rats was purified 450-fold as a marker of urate oxidase [EC 1.7.3.3.] activity. This preparation has a high specific activity of urate oxidase but not of other peroxisomal enzymes: D-amino acid oxidase [EC 1.4.3.3.], L-alpha-hydroxy acid oxidase [EC 1.1.3.15], or catalase [EC 1.11.1.6]. No activity of marker enzymes for other subcellular particles; cytochrome c oxidase [EC1.9.3.1] (mitochondria), acid phosphatase [EC 3.1.3.2] (lysosomes), or glucose-6-phosphatase [EC 3.1.3.9] (microsomes), was detected in this preparation. The core obtained showed a single protein band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the position of the band was found to correspond to a molecular weight 35,000. When the peroxisomal core was subjected to treatment at various pH's with 0.1 M carbonate buffer, urate oxidase was almost completely solubulized at pH 11.0, although approximately 35% of the core protein still remained in the pellet After solubilization of the core at pH 11.0, the specific activity of urate oxidase in the supernatant increased about 1.6 times; the density of the insoluble protein remaining in the pellet was identical with the that of the original core on sucrose density gradient centrifugation.
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PMID:Studies on peroxisomes. VI. Relationship between the peroxisomal core and urate oxidase. 0 33

Studies of the thermal stability of rat liver glucose-6-phosphatase (EC 3.1.3.9) were carried out to further elevate the proposal that the enzymic activity is the result of the coupling of a glucose-6-P-specific translocase and a nonspecific phosphohydrolase-phosphotransferase. Inactivation was observed when micorsomes were incubated at mild temperatures between pH 6.2 and 5.6. The rate of inactivation increased either with increasing hydrogen ion concentration or temperature. However, no inactivation was seen below 15 degrees in media as low as pH 5 or at neutral pH up to 37 degrees. The thermal stability of the enzyme may be controlled by the physical state of the membrane lipids and the degree of protonation of specific residues in the enzyme protein. Microsomes were exposed to inactivating conditions, and kinetic analyses were made of the glucose-6-P phosphohydrolase activities before and after supplementation to 0.4% sodium taurocholate. The results support the postulate and the kinetic characteristics of a given preparation of intact microsomes are determined by the relative capacities of the transport and catalytic components. Before detergent treatment, inactivation (i.e. a decrease in Vmax) was accompanied by a decrease in Km and a reduction in the fraction of latent activity, whereas only Vmax was depressed in disrupted preparations. The possibility that the inactivating treatments caused concurrent disruption of the microsomal membrane was ruled out. It is concluded that exposures to mild heat in acidic media selectively inactivate the catalytic component of the glucose-6-phosphatase system while preserving an intact permeability barrier and a functional glucose-6-P transport system. Analyses of kinetic data obtained in the present and earlier studies revealed several fundamental mathematical relationships among the kinetic constants describing the glucose-6-P phosphohydrolase activities of intact (i.e. the "system") and disrupted microsomes (i.e. the catalytic component). The quantitative relationships appear to provide a means to calculate a velocity constant (VT) and a half-saturation constant (KT) for glucose-6-P influx. The well documented, differential responses of the rat liver glucose-6-phosphatase system induced by starvation, experimental diabetes, or cortisol administration were analyzed in terms of these relationships. The possible influences of cisternal inorganic phosphate on the apparent kinetic constants of the intact system are discussed.
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PMID:Quantitative aspects of relationship between glucose 6-phosphate transport and hydrolysis for liver microsomal glucose-6-phosphatase system. Selective thermal inactivation of catalytic component in situ at acid pH. 1 Mar 5

Sorbitol density gradient centrifugation applied to intestinal mucosa homogenates resulted in a complete separation of soluble calcium-binding protein from the bound fraction of calcium-binding protein, providing further documentation of the bound pool of calcium-binding protein. The peak of the bound calcium-binding protein was not associated with the major peaks of any of the markers used, but was associated with minor peaks of alkaline phosphatase, RNA, and glucose-6-phosphatase. Lack of association of bound calcium-binding protein with (Na+ + K+)-ATPase indicated that the bound calcium-binding protein is not on the basolateral membrane. Differential centrifugation fractionation indicated that the bound calcium-binding protein is not associated with nuclei or mitochondria. The bound calcium-binding protein also could not be detected in partially purified brush borders. Exclusion of the brush border and basolateral membranes as the location of the bound calcium-binding protein suggests an intracellular locale.
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PMID:Studies on the subcellular localization of the membrane-bound fraction of intestinal calcium-binding protein. 11 17

Plasma membranes isolated from Yoshida ascites hepatoma AH-130 by a modification of the method of T.K. Ray (Biochim. Biophys. Acta 196:1, 1970), were subfractionated into three fractions having densities (d) 1.12, 1.14 and 1.16 by discontinuous sucrose density-gradient. Membrane subfractions were characterized by electron-microscopy, by assay of marker enzymes and by lipid composition. All subfractions appeared to be essentially free from whole mitochondria, lysosomes and nuclei. Subfraction d 1.16 had the highest 5'-nucleotidase, Mg++-ATPase and (Na+ +K+)-ATPase activities; cytochrome c oxidase was undetectable in any fraction and glucose-6-phosphatase was measurable only in fraction d 1.14 and 1.16. Cyclic AMP phosphodiesterase was nearly equally distributed in the fractions. Adenylate cyclase, 5'-nucleotidase and Mg++-ATPase activities of tumor membrane were lower with respect to liver plasma membrane, while cyclic AMP phosphodiesterase and (Na" +K+)-ATPase were found to have similar activities in the two membrane preparations. With respect to liver membrane, hepatoma membrane contained a higher amount of glycolipids and a higher amount of phospholipids accounted for mainly by sphingomyelin, phosphatidylserine and phosphatidic acid. The possible significance of the decrease of adenylate activity in the hepatoma membrane is briefly discussed.
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PMID:Isolation and characterization of the plasma membrane from Yoshida hepatoma cells. 16 55

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

Plasma membranes were isolated from rat liver mainly under isotonic conditions. As marker enzymes for the plasma membrane, 5'-nucleotidase and (Na+ + K+)-ATPase were used. The yield of plasma membrane was 0.6-0.9 mg protein per g wet weight of liver. The recovery of 5'-nucleotidase and (Na+ +K+)-ATPase activity was 18 and 48% of the total activity of the whole-liver homogenate, respectively. Judged from the activity of glucose-6-phosphatase and succinate dehydrogenase in the plasma membrane, and from the electron microscopic observation of it, the contamination by microsomes and mitochondria was very low. A further homogenization of the plasma membrane yielded two fractions, the light and heavy fractions, in a discontinuous sucrose gradient centrifugation. The light fraction showed higher specific activities of 5'-nucleotidase, alkaline phosphatase, (Na+ +K+)-ATPase and Mg2+-ATPase, whereas the heavy one showed a higher specific activity of adenylate cyclase. Ligation of the bile duct for 48 h decreased the specific activities of (Na2+ +K+)-ATPase and Mg2+-ATPase in the light fraction, whereas it had no significant influence on the activities of these enzymes in the heavy fraction. The specific activity of alkaline phosphate was elevated in both fractions by the obstruction of the bile flow. Electron microscopy on sections of the plasma membrane subfractions showed that the light fraction consisted of vesicles of various sizes and that the heavy fractions contained membrane sheets and paired membrane strips connected by junctional complexes, as well as vesicles. The origin of these two fractions is discussed and it is suggested that the light fraction was derived from the bile front of the liver cell surface and the heavy one contained the blood front and the lateral surface of it.
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PMID:Subfractionation of rat liver plasma membrane. Uneven distribution of plasma membrane-bound enzymes on the liver cell surface. 17 48

It is suggested that the specific involvement of phospholipid in either the expression or constraint of glucose-6-phosphatase activity is not conclusively established by the existing experimental evidence. The physiological significance of an apparent requirement for phosphatidylserine for Na+, K+-dependent adenosine triphosphatase activity is also questioned. The need for a critical reassessment of past conclusions in the light of present knowledge is emphasized.
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PMID:A reassessment of the phospholipid dependence of membrane-bound enzymes, with special reference to glucose-6-phosphatase and Na+, K+-dependent adenosine triphosphatase. 17 80

Female rats were injected subcutaneously with ethionine, and enzymic activities of liver membranes (Na+-k+-stimulated ATPase, Mg2+-stimulated ATPase, glucose-6-phosphatase, NADPH: cytochrome c oxido-reductase and NAD-nucleosidase) examined at proper intervals, during the intraperitoneal treatment of an egg phospholipid preparation (EPL). It is shown that EPL is unable to overcome the enzymic changes due to severe ethionine treatment, but is able to facilitate the recovery times after drug withdrawal for all the enzymic activities, except for NAD-nucleosidase. At lower dosage of the drug, the ethionine treatment is able to prevent the observed change of the glucose-6-phosphatase activity but not that of the Mg2+-ATPase. It is suggested that the EPL treatment may modify the chemical composition ahd/or architecture of liver membranes, altered by the ethionine injection, thus acting, at least partially, on the enzymic changes.
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PMID:The effect of egg phospholipid administration upon liver enzymic activities during ethionine treatment. 18 Dec 70

In this first paper of a series comparing the membranes of normal lymphocyte populations from male outbred Syrian hamsters with those of neoplastic transformants (GD 248) induced by simian virus 40, a method is described for the isolation of representative plasma membrane (PM) fragments from both cell types. Multiple criteria were used to monitor the purity and yield of PM material after cell disruption by nitrogen cavitation and after membrane fractionation by a combination of differential centrifugation and isopyknic ultracentrifugation in dextran density gradients. Lactoperoxidase-catalyzed radioiodination before cell disruption was used as an extrinsic surface marker; Na+,K+-activated ATPase, as well as alkaline phosphatase, was used as intrinsic functional PM markers. The distribution of nuclei, mitochondria, lysosomes, and endoplasmic reticulum (ER) during fractionation was monitored by the measurement of DNA, succinate dehydrogenase and monoamine oxidase, beta-glucuronidase and glucose-6-phosphatase, and NADH:lipoamide oxidoreductase, respectively. According to the three PM markers employed, a 15- to 20-fold purification (over homogenate) and a PM yield of about 65% were obtained for both cell categories, with negligible contamination by DNA, mitochondria, lysosomes, and er. The procedure also allowed recovery of 60% of the mitochondria free of other cell elements.
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PMID:Membranes of normal hamster lymphocytes and lymphoid cells neoplastically transformed by simian virus 40. I. High-yield purification of plasma membrane fragments. 18 92


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