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)

In 28 dogs the distal articular cartilage of the femur was removed and the regenerating articular surface on the 70th postoperative day was studied histochemically for hexokinase, glucose-6-phosphatase, phosphohexose-isomerase, fructose-1, 6-diphosphatase, aldolase, glyceraldehyde-3-phosphate dehydrogenase, lactate dehydrogenase, lactate dehydrogenase isoenzymes, phosphoglucomutase, phosphorylase, glycogen synthetase, UDP--glucose dehydrogenase, and UDP-glucuronic acid-4-epimerase. The articular surface consisted of fibrous tissue and of cartilage islets. The latter contained cells differentiating into cartilage and young chondrocytes. The glycolytic enzymes reacted positively in the regenerative articular surface. Enzyme activities were higher in the cells (particularly the chondroblasts and young chondrocytes) of the cartilage islets than in the connective tissue. In the cells differentiations into cartilage, beside the LDH isoenzymes characteristic of glycolysis, a significant LDH1 and LDH2 activity was observed. At the same site the presence of fructose-1, 6-diphosphatase-activity could be assumed, but there was no glucose-6-phosphatase activity. Glycogen synthesis proceeded in the cells of the cartilage islets and UDP-glucuronic acid-4-epimerase activity was observed in the differentiated cells. UDP-glucose dehydrogenase activity was positive in every section of the articular surface.
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PMID:Studies on cartilage formation. XX. Histochemical investigation of some enzymes of glycogen metabolsim in regenerative articular surfaces. 18 10

A liver perfusion system was assembled and adapted for pulse labelling studies. The perfusion medium was prepared by emulsifying perfluorotributylamine and Pluronic F 68 in a CO2 atmosphere using a sonicator. Ribosome-rich and ribosome-poor rough microsomes, smooth microsomes and Golgi membranes could be prepared from perfused livers with a good purity and recovery as from non-perfused livers. The subfractionation technique used was simple and involved slight modifications of the methods described earlier by Eriksson (1973) and Ehrenreich et al. (1973). The specific activity of NADPH-cytochrome c reductase in microsomes and of UDP-galactosyltransferase in Golgi membranes from perfused and non-perfused livers were identical. The specific activity of glucose-6-phosphatase in microsomes was slightly decreased after perfusion, but the membrane permeability barrier to glucose-6-phosphate remained intact. The granulated microsomal fractions from perfused liver had a somewhat reduced number of membrane-bound ribosomes. The system developed proved useful in studies of the synthesis and intracellular transport of albumin. The technique should also be suitable for use in studies of membrane biogenesis.
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PMID:The study of biogenetic pathways using a perfusion technique containing perfluorochemicals. 44 22

Male C3H/He, B6C3F1 and C57BL/6J mice were given a single injection of diethylnitrosamine (20 micrograms/g body wt) on day 15 after birth and animals were killed 17-29 (C3H/He and B6C3F1) and 29-46 weeks (C57BL/6J) after treatment. Carcinogen-induced liver lesions were identified by a deficiency in the marker enzyme glucose-6-phosphatase and the enzymatic phenotypes of these lesions were studied by enzyme and immunohistochemical methods using serial liver sections stained for seven additional histochemical markers. In all three mouse strains, liver lesions were characterized by an increased basophilia and a decreased expression of UDP-glucuronosyl-transferase, microsomal epoxide hydrolase and NADPH-cytochrome P450 reductase, while the cytochrome P450 isoenzymes 1A2, 2C6 and 2E1 were virtually unexpressed. Quantitative analyses revealed that throughout all periods of investigation, on average greater than 70% of the glucose-6-phosphatase-deficient lesions occupying up to 99% of the total volumetric fraction expressed concomitant alterations in at least one of these additional marker stainings. Upon determination of the phenotypic complexity levels, between 70 and 90% of lesions were found to contain alterations in at least six of the markers analysed, while lesions with alterations in less than three markers were comparatively infrequent. In the light of previous observations in the rat liver system, the relative homogeneity of enzyme phenotypes and the apparent lack of time-dependent changes in enzyme expression suggest that the majority of lesions of all three mouse strains possess an increased neoplastic character already from the very early beginning of the carcinogenic process in liver.
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PMID:Enzyme and immunohistochemical phenotyping of diethylnitrosamine-induced liver lesions of male C3H/He, B6C3F1 and C57BL/6J mice. 157 19

Among the therapeutic alternatives to orthotopic liver transplantation, hepatocyte transplantation (HT) offers the best potential in a number of liver diseases, mainly inborn errors of metabolism. Nevertheless, HT presents several inconveniences such as the scarce knowledge of the functionality of the transplanted hepatocytes, which has given rise to controversy about the specificity or unspecificity of the transplant, and the lack of a suitable system for preserving the cells. This study was designed to test a system for cryopreserving hepatocytes and to assess their functionality over prolonged periods after their ectopic transplantation. A medium and a freezing schedule which are reproducible and yield elevated viability have been used, and a number of hepatospecific parameters have been assessed: the activity of ornithine carbamoyltransferase--an enzyme of primary importance in the urea cycle--lipogenesis, gluconeogenesis, glucose-6-phosphatase and cytochrome oxidase activities, the presence of albumin--as an index of plasma protein synthesis--and IDA uptake and metabolism, showing the UDP-glucuronyl transferase activity. As dedifferentiation markers, gamma-glutamyl transpeptidase and alpha-fetoprotein have been studied. From the results, it can be deduced that hepatocytes can be cryopreserved and transplanted and that under these conditions they maintain hepatic features for a long time. Following transplantation, several specific liver functions appear or are enhanced in the spleen. Freshly isolated and cryopreserved transplanted hepatocytes have similar behaviors, although a difference in the expression of the function can be observed.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Auxiliary liver by transplanted frozen-thawed hepatocytes. 229 77

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

Plasma membranes from chick embryo neuronal primary cultures were isolated after subjecting 5-day-old cells, previously surface labeled with either lactoperoxidase-catalyzed radioiodination or galactose oxidase/NaB3H4, to a freeze-thaw cycle. The cellular material adhering to the culture substratum was washed, and the "wash" fractions were pooled and centrifuged at 37,000g. The resulting pellet was resuspended in 3 ml of buffer, layered on 33 ml of 33% sucrose, and centrifuged at 105,000g. Radioactivity was recovered at the top of the gradient. Sedimentation of these fractions and biochemical studies revealed that the pellet was 20- and 12-fold enriched in (Na+,K+)-adenosinetriphosphatase and 5'-nucleotidase, respectively. The preparation was devoid of inner mitochondrial (succinate dehydrogenase), outer mitochondrial (monoamine oxidase), endoplasmic reticulum (glucose-6-phosphatase), outer mitochondrial (monoamine oxidase), endoplasmic reticulum (glucose-6-phosphatase), and Golgi (UDP galactose:N-acetylglucosamine galactosyltransferase) enzymatic markers. Ultrastructural studies showed that the membrane preparation was homogeneous and lacked mitochondria endoplasmic reticulum and lysosomes. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate showed the presence of 11 protein components with molecular masses ranging from 120 to 300 kDa. This method for the isolation of plasma membranes probably depends on the capacity of the cellular material to adhere to the culture substratum and to entrap intracellular organelles during the freeze-thaw cycle. The membrane preparation seems suitable for studying the function of high-molecular-weight protein components of neuronal plasma membranes.
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PMID:Isolation of plasma membranes from neurons grown in primary culture. 282 51

Functional state of enzymatic systems in rat liver endoplasmic reticulum was studied. Content of cytochromes P-450 and b5 as well as activities of UDP-glucuronyl transferase, glucose-6-phosphatase, beta-glucuronidase, acetylesterase, inosine-5-diphosphatase were evaluated after permanent administration of nitrosodimethylamine within 2, 5 and 10 months at concentrations of 0.1, 1.0 and 10.0 mg/l. Content of the cancerogene active metabolites in liver cells was shown to be responsible for impairment of the functional state of microsomal enzymatic systems and was also related to intensity and duration of the nitrosodimethylamine effect. The level of these cancerogene metabolites in liver cells depended on rates of the cancerogene oxidation in the monooxygenase system and elimination of active products. At the same time, the rate of nitrosodimethylamine metabolism correlated with the doses of the substance administered into rats.
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PMID:[Effect of low concentrations of nitrosodimethylamine on the functional state of enzymatic systems in the endoplasmatic reticulum of the rat liver]. 283 31

The in vitro activities of glucose-6-phosphatase (G6P), UDP-glucuronyl transferase (GT) and P-450 were measured in liver homogenate and/or microsomal suspensions from puppies, 0-42 days of age (n = 26), and adult dogs (n = 3). For each of these enzymes, an age-related increase in the in vitro activity was observed, with the lowest value detected at birth. By the 28th-42nd day of postnatal life, P-450-specific activity was 350 and 85%, G6P 225 and 188%, p-nitrophenol GT 430 and 105% and bilirubin GT 317 and 123% of that seen in 0-hour-old puppies and adults dogs, respectively. The age-related changes in G6P and GT were observed when native enzymes or enzymes activated by deoxycholate or UDP-N-acetylglucosamine (GT) were used. However, the ratio between activated and native p-nitrophenol GT activity decreased as a function of age, and UDP-N-acetylglucosamine failed to activate bilirubin GT in puppies of 0-42 days of age. Total liver protein also increased with age, and hepatic water content was significantly higher in 0- to 42-day-old puppies (76.3%) than in adult dogs (71.4%). Thus, differences between puppies and adult animals were not the same when protein content or enzyme activities were expressed per unit of wet or dried liver weight. Phenobarbital, injected intraperitoneally at 15 mg/kg/day for 6 consecutive days to 8- to 13-day-old puppies (n = 3), produced induction of P-450 (235% of age-matched controls) and bilirubin GT activity (160%), diminished G6P activity (81%), and failed to modify p-nitrophenol GT activity (102%). These studies indicate that, in the puppy, (1) the in vitro activities of P-450, G6P and GT are immature at birth and develop during postnatal life; (2) as in other species, bilirubin and p-nitrophenol may be conjugated in the dog liver by two functionally distinct GT.
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PMID:Postnatal changes in hepatic microsomal enzyme activities in the puppy. 298 54

The effects of carbon disulfide (CS2) on the liver microsomal drug-metabolizing enzyme system and other enzyme activities were studied 1 hr after the oral administration of 3-300 mg/kg of CS2 in mice. Considerable decreases in drug-metabolizing enzyme activities (such as hydroxylation of aniline, O-dealkylation of p-nitroanisole, 7-ethoxycoumarin and 7-ethoxyresorufin, and N-demethylation of N,N-dimethylaniline), NADPH-cytochrome P-450 reductase (but not NADPH-cytochrome c reductase), and P-450-associated peroxidase activities were already observed at 3 and 30 mg/kg of CS2, dose dependently. At the same dosage levels, the magnitudes of microsomal spectral changes induced by aniline and nicotinamide (type 2 substrates), but not those induced by hexobarbital and SKF-525A (type 1 substrates), were also reduced to a considerable extent. The degrees of these alterations were all greater than that of the measurable loss of P-450 content, i.e. the loss of functional activity of P-450 was much greater than simply expected from the apparent decrease in the hemoprotein content. Cytochrome b5 content and NADH-ferricyanide reductase activity were unchanged at 30 and 300 mg/kg of CS2, although NADH-cytochrome c reductase activity was increased at the latter dose. The following enzyme activities did not change significantly at up to 300 mg/kg of CS2: flavin-containing monooxygenase, UDP-glucuronyl transferase, glucose-6-phosphatase and heme oxygenase in microsomes, and glutathione S-transferases in the soluble fraction. Microsomal conjugated diene levels and liver glutathione content were also unchanged. These observations support the theory that P-450 is a sensitive and selective site for CS2 action, where CS2 itself is bioactivated. It was also shown that the loss of P-450 was reversible after a single, or repeated, administration of CS2.
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PMID:Early, selective and reversible suppression of cytochrome P-450-dependent monooxygenase of liver microsomes following the administration of low doses of carbon disulfide in mice. 377 18

The saturation of the fat contained in the diet has been observed to affect the acylcoenzyme A:cholesterol acyltransferase (ACAT) activity of rat liver microsomes. ACAT activity in microsomes (Mp) prepared from livers of rats fed a polyunsaturated fat-enriched diet containing 14% sunflower seed oil was 70-90% higher than in microsomes (Ms) prepared from livers of rats fed a saturated fat-enriched diet containing 14% coconut oil. This difference was observed within 20 days after the diets were begun, the earliest time tested, and persisted throughout the 70-day experimental period. The difference was noted at all [1-14C]palmitoyl CoA concentrations tested, 2.5-33 micronM, and at temperatures between 18 and 40 degrees C. Arrhenius plots revealed a single transition in enzyme activity, occurring at 29 degrees C in both microsomal preparations. Likewise, the activation energy above this transition was the same in Mp and Ms, 12.5 KCal/mol. Addition of albumin to the incubation medium increased the ACAT activity of both microsome preparations, but the difference between Mp and Ms persisted. Mp was enriched in polyenoic fatty acids, primarily 18:2 and 20:4, while Ms was enriched in monoenoic acids. Although the 20:4 increase in Mp occurred in all phosphoglycerides, it was especially pronounced in the serine and inositol phosphoglyceride fraction. There were no differences in the phospholipid or cholesterol content, phospholipid head group composition, or protein composition of the two microsomal preparations. The possibility is discussed that the changes in ACAT activity result from the differences in fatty acid composition of the microsomes. Other microsomal enzymes exhibited varying responses to these dietary fatty acid modifications. Palmitoyl CoA hydrolase and NADPH cytochrome c reductase activities were unchanged. UDP glucuronyl transferase activity was 50% higher in Mp, but glucose-6-phosphatase and NADH cytochrome b5 reductase activities were 25% higher in Ms. Therefore, dietary fat modifications do not produce a uniform effect on the activity of microsomal enzymes.
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PMID:Effect of dietary fat saturation on acylcoenzyme A:cholesterol acyltransferase activity of rat liver microsomes. 610 16


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