Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

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. Limulus hepatopancreas, coxal glands and intestine contain a particulate enzyme which can synthesize glucose 6-phosphate from glucose and inorganic pyrophosphate or carbamyl phosphate as well as hydrolyze glucose 6-phosphate. This has been clearly differentiated from hydrolysis by lysosomal or soluble phosphatases. 2. The enzyme resembles vertebrate glucose-6-phosphatase in its specific anatomical distribution, pH optimum, kinetic properties, donor specificity and phospholipid dependence, as indicated by its satency and lability to detergent treatment. 3. A variety of other invertebrates tested exhibited little or no PPi-glucose phosphotransferase activity with these properties. A similar phosphotransferase activity of lobster hepatopancreas had somewhat different kinetic properties and pH optimum. 4. The hypothesis that a specific glucose-6-phosphatase is to be found only in those animals which utilize free glucose as an important circulating form of energy is presented and discussed. It appears that a variety of transport compounds, such as trehalose and glucose, was tried at the evolutionary level of the Arthropods.
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PMID:A Limulus glucose-6-phosphatase with phosphotransferase activity characteristic of vertebrate liver microsomes. Its possible evolutionary significance. 18 9

We demonstrate that glucose-6-phosphatase, pyrophosphate-glucose phosphotransferase, carbamyl phosphate-glucose phosphotransferase and inorganic pyrophosphatase activities are deficient in livers of patients with type I glycogen storage disease. This provides strong genetic evidence that these enzymatic activities reside in a single protein or share a common polypeptide chain.
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PMID:Genetic evidence for the common identity of glucose-6-phosphatase, pyrophosphate-glucose phosphotransferase, carbamyl phosphate-glucose phosphotransferase and inorganic pyrophosphatase. 18 42

The effect of alloxan-diabetes, and of pharmacological doses of hydrocortisone administered to normal and diabetic rats, on carbamyl phosphate:glucose phosphotransferase and D-glucose-6-phosphate phosphohydrolase (EC 3.1.3.9) activities of isolated hepatic nuclei and microsomes were studied by assay at pH 7 in the absence and presence of deoxycholate. Hormonally related alterations both in activity levels and in the activation by the detergent (i.e. latency) of activities of the two cellular structural elements differed significantly. Most strikingly, (a) a 3--4-fold increase in the levels of activities of nuclei was seen in response either to diabetes or to hydrocortisone administered to normal rats whether or not detergent was added to preparations prior to assay; (b) the normally low degree of stimulation by detergent of activities of nuclei was unaltered in diabetes, and (c) administration of the glucocorticoid to diabetic rats decreased activity levels and increased their activation by detergent. Directly contrasting responses were noted with isolated microsomal preparations. Fundamental differences in the enzymes in these two organelle preparations are thus demonstrated. It appears that both synthetic and hydrolytic activities of this enzyme of nuclei may be manifest in the presence of requisite substrates, and that activities of this organelle may become increasingly prominent under certain hormonally perturbed conditions.
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PMID:Responses of nuclear glucose-6-phosphatase to diabetes and to hydrocortisone administered to normal and diabetic rats differ from those of the microsomal enzyme. 22 43

Kinetic studies indicate that glucose-6-phosphatase is a multifunctional enzyme. a) Phosphohydrolase activities. The mannose-6-phosphatase activity is low (Km = 8 mM, VM = 90 nmoles. min-1mg-1). The enzyme shows a strong affinity for glucose-6-phosphate (Km = 2.5 mM, VM = 220 nmoles.min-1mg-1). beta-glycerophosphate (K1 = 30 mM), D-glucose (Ki = 120 mM) are mixed type inhibitors; pyrophosphate (Ki = 2 mM) is a non competitive one. b) Phosphotransferase activities. Di and triphosphate adenylic nucleosides or phosphoenol pyruvate are not substrates. Carbamylphosphate serves as a phosphoryl donor with D-glucose as acceptor. The phosphate transfer is consisstent with a random mechanism in which the binding of one substrate increases the enzymes affinity for the second substrate. Apparent Km values for carbamyl-phosphate range from 5.2 mM (D-glucose concentration leads to infinity) to 8 mM (D-glucose concentration leads to 0). The corresponding apparent Km values for D-glucose are 59 mM (carbamyl-phosphate concentration leads to infinity) to 119 mM (carbamyl-phosphate concentration leads to 0). Maximal reaction velocity with infinite levels of both substrates is 270 nmoles.min-1.mg-1. Pyrophosphate is a poor phosphoryl donnor (Km = 55 mM with D-glucose concentration 250 mM). In addition we do not find any latency; detergents, namely sodium deoxycholate, Triton X 100 do not affect or inhibit glucose-6-phosphatase activity.
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PMID:[Monkey liver microsomal glucose-6-phosphatase]. 23 60

The presence of carbamyl-phosphate:glucose phosphotransferase in liver nuclei of five species of mammals and birds is demonstrated. The activity is confined to nuclear membranes and is due exclusively to multifunctional glucose-6-phosphatase-phosphotransferase (D-glucose-6-phosphate phosphohydrolase; EC 3.1.3.9). The nuclear enzyme constitutes approximately 16 to 19 percent of total hepatic glucose-6-phosphatase-phosphotransferase. Carbamyl-phosphate:glucose phosphotransferase and glucose-6-P phosphohydrolase activities of membrane of chicken liver nuclei are shown to be catalytically identical with the maximally activated microsomal enzyme. A correspondence is seen in two-substrate kinetic double reciprocal plots, K-m or apparent K-m values for the various substrates, K-i values for the competitive inhibitors P-i and ATP, and pH-activity profiles. Comparative studies were carried out with various intact, disrupted, and detergent-dispersed membranous preparations by a combination of enzyme kinetic and electron microscopic techniques. It is concluded that (a) intimate interrelationships exists between catalytic behavior of this enzyme and morphological integrity of membranes of which the enzyme is a part; (b) activities of the enzyme of nuclear membrane appear quite available for physiological phosphorylative functions; and (c) interrelationships between membrane morphology and catalytic behavior of this membrane-bound enzyme may well be involved in the bioregulation of this complex, multifunctional enzyme system.
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PMID:Carbamyl phosphate: glucose phosphotransferase and glucose-6-phosphate phosphohydrolase of nuclear membrane. Interrelationships between membrane integrity, enzymic latency, and catalytic behavior. 23 53

The ability of glucose 6-phosphate and carbamyl phosphate to serve as substrates for glucose-6-phosphatase (D-glucose-6-phosphate phosphohydrolase; EC 3.1.3.9) of intact and disrupted microsomes from rat liver was compared at pH 7.0. Results support carbamyl phosphate and glucose 6-phosphate as effective substrates with both. Km values for carbamyl phosphate and glucose 6-phosphate were greater with intact than with disrupted microsomes, but Vmax values were higher with the latter. The substrate translocase-catalytic unit concept of glucose-6-phosphatase function is thus confirmed. The Km values for 3-O-methyl-D-glucose and D-glucose were larger when determined with intact than with disrupted microsomes. This observation is consistent with the involvement of a translocase specific for hexose substrate as a rate-influencing determinant in phosphotransferase activity of glucose-6-phosphatase.
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PMID:Comparative reactivity of carbamyl phosphate and glucose 6-phosphate with the glucose-6-phosphatase of intact microsomes. 300 88

The effect of 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide (CMC) on the reactions catalyzed by the glucose-6-phosphatase system of rat liver microsomes was studied. Modification of the intact microsomes by CMC leads to the inhibition of the glucose-6-phosphatase, pyrophosphate:glucose and carbamoyl-phosphate : glucose phosphotransferase activities of the system. The activities are restored by the disruption of the microsomal permeability barrier. The mannose-6-phosphate, pyrophosphate, and carbamoyl-phosphate phosphohydrolase activities of the intact as well as the disrupted microsomes were not affected by CMC. It follows from the results obtained that CMC inactivates the microsomal glucose-6-phosphate translocase, the inactivation is a result of the modification of a single sulfhydryl or amino group of the translocase; pyrophosphate, carbamoyl phosphate and inorganic phosphate are transported across the microsomal membrane without participation of the glucose-6-phosphate translocase; pyrophosphate and carbamoyl phosphate may act as the phosphate donors in the glucose phosphorylation reactions in vivo.
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PMID:The effect of 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide on the rat liver microsomal glucose-6-phosphatase system. 302 57

In children with Reye's syndrome, liver specimens exhibit the following characteristics: mitochondrial dysfiguration, fatty infiltration, decreased activity of carbamyl phosphate synthetase and of ornithine transcarbamylase, histochemically reduced activity of succinic dehydrogenase and cytochrome oxidase, and depletion of glycogen. We intended to create an animal model for Reye's syndrome by treating mice with encephalomyocarditis virus, and/or salicylate, fructose, Atlox, butylated hydroxytoluene, pentachlorophenol, and an equal mixture of butylated hydroxytoluene and monosodium stearate. Liver specimens were then examined for the listed characteristics as well as for the activity of argininosuccinic lyase, arginase, phosphorylase, and glucose-6-phosphatase. Results of interest in regard to the experimental intention were obtained in livers of mice treated with virus and Atlox (A) or virus and butylated hydroxytoluene (B). In these specimens, we found a significant reduction (p less than 0.05)--except for ornithine transcarbamylase (A)--to the following levels (in percentage of normal mean): carbamyl phosphate synthetase (A, 79 per cent; B, 57 per cent); ornithine transcarbamylase (A, 91 per cent; B, 75 per cent); glycogen (A, 26 per cent; B, 37 per cent). Simultaneous morphologic analysis of these liver specimens indicated mitochondrial dysfiguration, absence of dense granules, fatty infiltration, and normal activity of succinic dehydrogenase and cytochrome oxidase. The induction of Reye's syndrome-like features in mouse liver may be useful for the study of disease mechanisms and therapy.
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PMID:Reye's syndrome simulacra in liver of mice after treatment with chemical agents and encephalomyocarditis virus. 626 2

Vanadate has been found to be a potent inhibitor of both the hydrolytic and synthetic activities of the multifunctional enzyme glucose-6-phosphatase (D-glucose-6-phosphate phosphohydrolase, EC 3.1.3.9). The enzyme, when studied in both microsomal preparations and in situ using permeable isolated hepatocytes, is inhibited by micromolar concentrations of vanadate. The inhibition by vanadate is greater in detergent-treated than in untreated microsomes. In both the microsomal preparations and permeable hepatocytes, the inhibition by vanadate is competitive with the phosphate substrate and is greater for the phosphotransferase than the hydrolase activity of the enzyme. The Ki values of vanadate for carbamyl-phosphate : glucose phosphotransferase and glucose-6-phosphate phosphohydrolase determined with permeable hepatocytes are in good agreement with the values determined with detergent-dispersed microsomes. The previously described inhibition of glucose-6-phosphate phosphohydrolase by ATP (Nordlie, R.C., Hanson, T.L., Johns, P.T. and Lygre, D.G. (1968) Proc. Natl. Acad. Sci. USA 60, 590-597) can now be explained by the vanadium contamination of the commercially available ATP samples used. In contrast with glucose-6-phosphatase, hepatic glucokinase and hexokinase were not inhibited by vanadate. Physiological implications and utilitarian experimental applicability of vanadate as a selective metabolic probe, based on these observations, are suggested.
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PMID:Vanadate: a potent inhibitor of multifunctional glucose-6-phosphatase. 627 21


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