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)

Membranes from chick embryo epiphyseal cartilage were fractionated by equilibrium sucrose density gradient centrifugation and assayed for galactosyl xylose transferase, chondroitin polymerization and sulfation as well as the marker enzymes glucose-6-phosphatase, NADH cytochrome c reductase, galactosyl ovalbumin transferase, and sialyltransferase. The order of distribution of chondroitin sulfate synthesis from dense to light membranes correlated with the established sequence of events for its synthesis. The linkage region enzyme, viz. galactosyl xylose transferase, distributed with NADH cytochrome c reductase in an earlier and heavier cis compartment. Chondroitin polymerization and sulfation had a dual distribution similar to the galactosyl ovalbumin transferase and sialyltransferase in separate later and lighter medial and trans compartments, or in an extended medial or trans compartment. The galactosyl xylose transferase had a distribution distinctly different from that of the galactosyl ovalbumin transferase indicating that these distinct enzymes showed no cross-reactivity with their respective acceptor substrates. The dual distribution of chondroitin sulfate synthesis was consistent with our previous demonstration of the two nascent proteochondroitin populations produced by microsomal preparations from the same source. The results indicated separate subcellular locations for synthesis of the two forms.
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PMID:Subfractionation of chick embryo epiphyseal cartilage Golgi. Localization of enzymes involved in the synthesis of the polysaccharide portion of proteochondroitin sulfate. 185 50

Antibodies against cytochrome P-450 are found in some children with autoimmune hepatitis (antiliver/kidney microsome 1) and in patients with ticrynafen hepatitis (antiliver/kidney microsome 2). For an immune reaction against cytochrome P-450 to possibly destroy the hepatocytes, one must assume that cytochrome P-450 is present on the plasma membrane surface of hepatocytes. In a first series of experiments, plasma membranes were prepared with a technique based on the electrostatic attachment of isolated hepatocytes to polyethyleneimine-coated beads. After vortexing, beads were coated with a very pure plasma membrane fraction. Microsomal contamination, judged from the specific activities of glucose-6-phosphatase or NADH-cytochrome c reductase, was less than 1%. Nevertheless, the specific content (per milligram of protein) of CO-binding cytochrome P-450 was 20% of that in microsomes; the specific benzo(a)pyrene hydroxylase activity was 25%, and ethoxycoumarin deethylase 11%. Immunoblots showed the presence of cytochromes P-450 UT-A, UT-H, PB-B, ISF-G and PCN-E, the last three isoenzymes being inducible by, respectively, phenobarbital, 3-methylcholanthrene and dexamethasone. In a second series of experiments, nonpermeabilized isolated hepatocytes from untreated rats were incubated with anticytochrome P-450 antibodies. Immunofluorescence and immunoperoxidase staining confirmed the presence of cytochromes P-450 UT-A, PB-B and ISF-G on the membrane. In a last series of experiments, human antiliver-kidney microsomal 1 antibodies were found to react specifically with rat liver plasma membrane cytochrome P-450 UT-H (IID subfamily). We conclude that several cytochrome P-450 isoenzymes are present, active and inducible on the plasma membrane surface of hepatocytes. It is therefore conceivable that immunization against plasma membrane cytochrome P-450 might lead to the immunological destruction of hepatocytes in some patients.
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PMID:Presence of functional cytochrome P-450 on isolated rat hepatocyte plasma membrane. 211 12

Experimental infection of golden hamsters with the hookworm, Ancylostoma ceylanicum, caused a profound decline in the hepatic microsomal cytochrome P450 content. Concomitant decrease was also noticed in aminopyrine N-demethylase and benzo[a]pyrene hydroxylase activities. However, aniline hydroxylase activity was only marginally elevated during the infection. Microsomal markers, viz., cytochrome b5, NADH-cytochrome-c reductase, and glucose-6-phosphatase, were not significantly altered. Hepatic tissue exhibited an accumulation of lipids, especially phospholipids, triglycerides, and cholesterol, resulting in fatty necrosis around the central vein region. Isolated hepatic microsomes showed a decrease in phosphatidylcholine content. Impairment in hepatic mixed function oxidase (MFO) activities was further confirmed by prolongation in hexobarbital sleeping time and zoxazolamine-induced paralysis. The hepatic MFO system of A. ceylanicum-infected hamsters responded qualitatively and quantitatively in a manner similar to that of control hamsters, upon stimulation with selective chemical inducers like phenobarbitone and 3-methylcholanthrene. Kinetic and in vitro substrate binding studies revealed that for aminopyrine the substrate affinity and the maximum enzyme activity (Vmax) were decreased, while for aniline the binding affinity was decreased and the binding capacity was enhanced. Results indicate specific/selective impairment of the hepatic microsomal cytochrome P450 system during hookworm infection and may have many practical implications in toxicology and pharmacology.
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PMID:Hepatic microsomal cytochrome P450 system during experimental hookworm infection. 236 36

Inositol 1,4,5-trisphosphate [Ins(1,4,5)P3], arising from hydrolysis of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2], is proposed as the link between membrane-receptor activation and mobilization of Ca2+ from intracellular sites in hormone-secreting cells. The location of Ins(1,4,5)P3-sensitive membranes was investigated in cultured neonatal beta-cells. Membranes were obtained after lysis of cells attached to positively charged Sephadex. After lysis the presence of the enzyme markers 5'-nucleotidase, glucose-6-phosphatase, NADH-cytochrome c reductase, UDP-galactosyltransferase and succinate dehydrogenase indicated the mixed nature of the preparation. After sonication, however, UDP-galactosyltransferase and succinate dehydrogenase activities were undetectable, but 4.8% of total cellular glucose-6-phosphatase and 3.4% of total cellular NADH-cytochrome c reductase remained with 5'-nucleotidase in the preparation, indicating endoplasmic-reticulum association. ATP-dependent 45Ca2+ accumulation was shown in this preparation (410 +/- 24 pmol/mg of protein at 150 nM free Ca2+) and was inhibited by vanadate (100 microM). Ca2+ release was effected by Ins(1,4,5)P3, with half-maximal release at 0.5 +/- 0.14 microM-Ins(1,4,5)P3, t1/2 11.2 +/- 1.1 s. GTP- and guanosine 5'-[beta gamma-imido]triphosphate (p[NH]ppG)-promoted release of 45Ca2+ was demonstrated in this preparation, but the kinetics of release (half-maximal Ca2+ release at 5.4 +/- 0.7 microM, with t1/2 77.3 +/- 6.9 s, and at 51.1 +/- 4.2 microM, with t1/2 19.0 +/- 2.2 s, for GTP and p[NH]ppG respectively), and the ability of neomycin sulphate to block p[NH]ppG-induced release only, are indicative of separate release mechanisms after treatment with these agents. A close association between plasma membrane and elements of the endoplasmic reticulum is indicated in this model, providing a possible mechanism for local alterations in free Ca2+ in the sub-plasma-membrane region.
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PMID:GTP- and inositol 1,4,5-trisphosphate-induced release of 45Ca2+ from a membrane store co-localized with pancreatic-islet-cell plasma membrane. 245 19

Inclusion bodies containing glycogen-enzymes were found in 30 to 60% of type 2 fibres of tenotomized calf muscles (m. gastrocnemius, m. soleus, m. plantaris) in rats, using histochemical reactions. The bodies appeared within 1 week after the tenotomy and were localized both in the central and the subsarcolemmal regions and rarely extruded into the extracellular space. These aggregates are 3 to 15 microns in length and 2 to 11 microns in diameter. In addition to glycogen, these bodies also contained various enzymes of the glycogen metabolism such as phosphorylase, a branching enzyme, and glucose-6-phosphatase, but showed no NADH-reductase, lactate dehydrogenase, or myofibrillar ATP-ase activity. The results indicate that glycogen-enzymes containing bodies are a degenerative phenomenon, which occurs only in type 2 fibres of the tenotomized muscles.
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PMID:Glycogen-enzymes containing bodies in type 2 fibres of tenotomized muscles in the rat. 255 27

Oxidation of diethyldithiocarbamate (DTC) to disulfiram (DS) by liver microsomes was tested in vitro by using a copper-DTC chelate formation reaction after the conversion of DS to DTC by glutathione (GSH). In the presence of NADPH, microsomes produced DS from DTC in both the free and microsome-bound forms, the former being greater than the latter. DS production was dependent on NADPH and DTC concentrations, and incubation time. Increases in microsomal concentrations, up to a certain level, also increased the free and total DS production. NADH was only somewhat effective, both the exposure to a nitrogen atmosphere and heat-denaturation of the microsomes suppressed the reaction. Preincubation of microsomes with both DTC and NADPH markedly decreased aniline hydroxylase, p-nitroanisole O-demethylase and glucose-6-phosphatase activities, and moderately decreased NADH-ferricyanide and NADH-cytochrome c reductase, but NADPH-cytochrome c reductase was minimally affected. DTC alone had only slight effects on the activities. DS also decreased these enzyme activities, particularly glucose-6-phosphatase; the loss of NADPH-cytochrome c reductase activity being protected in the presence of NADPH. GSH almost completely prevented the loss of microsomal enzyme activities induced by DTC and NADPH except for the drug metabolizing activities, in which protection was incomplete. The microsomal oxidation of DTC to DS could play a role in the action of DS in the liver, since DS is rapidly degradated to DTC in vivo.
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PMID:Oxidation of diethyldithiocarbamate to disulfiram by liver microsomes in the presence of NADPH and subsequent loss of microsomal enzyme activity in vitro. 285 81

The cholesterol content of rat liver microsomal membranes was modified in vitro by incubating microsomes and cytosol with liposomes prepared by sonication of microsomal lipids and cholesterol. In this way, the cholesterol to phospholipid molar ratio was increased from 0.11-0.13 in untreated microsomes to a maximal of 0.8 in treated ones. Cholesterol incorporation in microsomes produced an increase in the diphenyl-hexatriene steady-state fluorescence anisotropy and a decrease in the efficiency of pyrene-excimer formation which indicated a decrease in the rotational and translational mobility, respectively, of these probes in the membranes lipid phase. Cholesterol incorporation in microsomes did not affect significantly the glucose-6-phosphatase activity in 0.1% Triton X-100 totally disrupted microsomes, but diminished the glucose-6-phosphatase activity of 'intact' microsomes. This indicates that possibly the glucose 6-phosphate translocation across the microsomal membrane is impeded by an increase in the membrane apparent 'microviscosity'. Cholesterol incorporation in microsomes decreased NADH-cytochrome c reductase without affecting NADH-ferricyanide reductase activity. The delta 9 desaturation reaction rate was enhanced by cholesterol incorporation at low but not at high palmitic acid substrate concentration. delta 5 and delta 6 desaturase reaction-rates were increased both at low and high fatty acid substrate concentrations. These results suggest that a mechanism involving fatty acid desaturase enzymes, might exist to self-regulate the microsomal membrane lipid phase 'fluidity' in the rat liver.
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PMID:In vitro modification of cholesterol content of rat liver microsomes. Effects upon membrane 'fluidity' and activities of glucose-6-phosphatase and fatty acid desaturation systems. 299 32

Based on cytochemical analysis, the enzyme NADP phosphatase is most concentrated in the so-called intercalary cisternae from the mid-region of the Golgi apparatus stack. Using free-flow electrophoresis to separate different Golgi regions of rat liver Golgi apparatus, the NADP phosphatase activity, based on estimation of the rate of release of inorganic phosphate from NADP under standard conditions, was similarly localized to membrane fractions from the center of electrophoretic separations. Peak specific activities for both a putative cis marker (NADH-cytochrome c reductase) and an established trans marker (galactosyltransferase) coincided with minima in NADP phosphatase activity, in agreement with the cytochemical observations. The pattern of distribution of enzyme activity for NADP phosphatase differed from that of both acid phosphatase and glucose-6-phosphatase. The pH optimum was 5.0, the Km for NADP was 0.6 mM and a corresponding production of NAD and inorganic phosphorus was shown. Taken together with other markers for free-flow electrophoresis separation, the NADP phosphatase will provide considerable utility as a specific marker to help identify intercalary cisternae of the mammalian Golgi apparatus and to monitor electrophoretic separations.
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PMID:NADP phosphatase as a marker in free-flow electrophoretic separations for cisternae of the Golgi apparatus midregion. 300 95

Female albino mice were fed sublethal doses of KCN (approx. 10 micrograms/mouse/day) for 7 days, injected intraperitoneally with phenobarbitone (50 mg/kg body wt/day) in the subsequent 3 days, and sacrificed 24 hr after the last injection. Phenobarbitone sleeping time was increasingly shortened (16-27%) daily in cyanide-fed mice in comparison with cyanide-free controls. Both compounds administered singly or simultaneously increased the liver weight/body weight ratios by not more than 10%. Aniline hydroxylase, glucose-6-phosphatase, NADPH- and NADH-cytochrome c reductase activities were similarly increased. Aniline hydroxylase activity was most markedly increased (by a factor of 4). The toxicological implications of these results are discussed.
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PMID:Hepatic effects of phenobarbitone in female mice fed sublethal levels of dietary cyanide. 302 73

Aniline hydroxylase, glucose-6-phosphatase, NADPH- and NADH-cytochrome C reductase activities were measured in liver microsomes prepared from four groups of female mice. Mice were fed either control diets alone or KCN (0.357, microgram/kg body wt/day) supplemented diets or control diets plus AFB1 (0.35 microgram/kg body wt/day) administration (ip) on the 8, 9 and 10th day or the KCN supplemented diet plus AFB, administration (ip) on the 8, 9 and 10th day. KCN and AFB1 consistently elevated the activities of the enzymes. Simultaneous administration of both toxins potentiated their effects on the enzymes with the exception of glucose-6-phosphatase. Increases in microsomal protein/liver wt ratios, liver wt/body wt ratios and these enzyme activities were probably indicative of microsomal enzyme induction.
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PMID:Effect of aflatoxin B1 on some liver microsomal enzymes in mice fed cyanide supplemented diets. 310 4


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