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)

Previous work from this laboratory indicates that glucokinase serves as the glucose sensor of pancreatic islets. Here we show by nonlinear computer optimization that the kinetic properties of glucokinase (together with hexokinase, known to be present in islets) account for the observed glycolytic rates in islets as a function of glucose level. Alternative enzymes that have been suggested to perform the same function as glucokinase, N-acetyl-D-glucosamine kinase and glucose-6-phosphatase, are shown to have incompatible properties, including a poor fit, different curve shapes, and unreasonable parameter values resulting from optimization. Their activities in islets are shown to be too low to account for observed glucose usage rates. This work endorses our previous proposal that glucokinase acts as the glucose sensor in pancreatic islet cells.
Am J Physiol 1984 Sep
PMID:Computer modeling identifies glucokinase as glucose sensor of pancreatic beta-cells. 608 96

The subcellular localization of glutamine synthetase, an enzyme fundamental to the compartmentation of glutamate hypothesis, was investigated using brain tissue of adult rats. The distribution of this enzyme in relation to the distribution of glucose-6-phosphatase, glutamate dehydrogenase and acetycholine esterase was studied using a fractionation scheme which had been previously extensively characterized in terms of intramitochondrial enzyme complements. Glutamine synthetase was found to be predominantly localized at the nerve terminal and a number of results suggested a possibble association with the synaptic membrane. The observations are discussed in relation to the compartmentation of glutamate metabolism. Acetate and ammonia are precursors of the 'small' pool of glutamate from which most of the synthesis of glutamine occurs. Since one population of synaptic mitochondria has previously been shown to be enriched in glutamate dehydrogenase and acetyl CoA synthetase and in view of the current observtions that synaptosomes are probably in association with a large proportion of brain glutamine synthetase, it is tentatively suggested that the synaptic complex represents at least in part the site of the 'small' glutamate pool.
Brain Res 1980 Sep 22
PMID:The distribution of glutamine synthetase in subcellular fractions of rat brain. 610 1

Prostaglandins E1 and E2 are specifically bound by particulate fractions from bovine adrenal medulla. The subcellular localization of these binding sites has been investigated by comparing their distribution in subcellular fractions obtained by differential and gradient centrifugation to those of marker enzymes for various organelles. Prostaglandin E2 binding sites were purified about 16-fold with respect to the homogenate in a fraction which was highly enriched in plasma membranes on the basis of the activities of the marker enzymes acetylcholinesterase and calcium-dependent ATPase, which were both purified by about 12-fold in this fraction. The plasma membrane fraction contained relatively low activities of marker enzymes for mitochondria (monoamine oxidase), lysosomes (acid phosphatase), endoplasmic reticulum (glucose-6-phosphatase), Golgi (galactosyl transferase) and chromaffin granule membranes (dopamine beta-hydroxylase). The only other fractions enriched in prostaglandin E2 binding sites were those for the endoplasmic reticulum and the Golgi, in which the binding sites were purified about 4-fold and 7-fold, respectively. This is probably due mainly to contamination with plasma membranes, since calcium-dependent ATPase and acetylcholinesterase were each purified to a similar extent in these two fractions. These data suggest that the high-affinity prostaglandin E2 binding sites of the adrenal medulla are localized primarily on the plasma membranes of the medullary cells.
Biochim Biophys Acta 1984 Sep 28
PMID:Subcellular localization of prostaglandin E2 binding sites in bovine adrenal medulla. 614 8

Crude microsomes from porcine endometrium and three subfractions obtained by a modification of Rothschild's technique were characterized by RNA/protein ratio, marker enzyme activities and morphological appearance. The microsomes were devoid of glucose-6-phosphatase activity. They contained approximately 10% of arylesterase-, approximately 30% of both NADPH-cytochrome reductase- and UDPgalactose-N-acetyl-glucosamine beta-D-galactosyltransferase- and approximately 60% of 5'-nucleotidase activities present in the homogenates. Subfraction I (smooth membranes) had twice the galactosyltransferase activity of Subfraction II (smooth and rough membranes + free ribosomes); both subfractions were rich in 5'-nucleotidase and cytochrome reductase activities. Subfraction III (rough membranes) had very low marker activities but exhibited the highest RNA/protein ratio, which was lowest in I.
Hoppe Seylers Z Physiol Chem 1983 Sep
PMID:Characterization of microsomal subfractions from porcine endometrium cells. 619 68

The food intake, gut weight, gut length, mucosal protein and mucosal activities of alkaline phosphate (EC 3.1.3.1), acid phosphate (EC 3.1.3.2), isocitric dehydrogenase (EC 1.1.1.42) and glucose-6-phosphate (EC 3.1.3.9) were measured in rats during pregnancy, lactation and after the young were weaned. In general, the quantities measured increased slightly during pregnancy and considerably during lactation, reaching maximum values during the 3rd weeks of lacation and falling more or less rapidly after the young were weaned to the same levels as those in unmated animals. However, the gut length and mucosal protein remained higher even 3 weeks after weaning, so that weight per unit length and specific enzyme activities (per mg protein) tended to be lower in mated than in unmated rats. Changes in the specific activities of enzymes indicate alterations of the metabolic function of the enterocytes during breeding similar to changes reported for digestive enzymes. It is suggested that the intestine may reflect changes that take place in the liver.
J Reprod Fertil 1980 Sep
PMID:Activities of some metabolic enzymes in the small intestinal mucosa during pregnancy and lactation in the rat. 625 36

Inhibition of rat liver microsomal glucose-6-phosphatase (D-glucose-6-phosphate phosphohydrolase, EC 3.1.3.9) by orthophosphate and organophosphate esters was examined at pH 6.0 and 7.5 with and without enzyme pretreatment with 0.2% (w/v) deoxycholate. Inhibition by orthophosphate and monoethyl phosphate was competitive with respect to glucose-6-P while inhibition by mono- and di-phenyl phosphate was of the mixed type. Monoalkyl phosphates were more effective inhibitors than the analogous di- and tri-alkyl phosphates and deoxycholate potentiated the inhibitory effects. Mono- and di-phenyl phosphates were more effective inhibitors than triphenyl phosphate, and deoxycholate decreased these inhibitory effects. The results are interpreted in terms of inhibitor and deoxycholate interactions with the enzyme.
Can J Biochem 1980 Sep
PMID:Inhibition by orthophosphate esters of glucose-6-phosphatase. 625 51

Hereditary fructose intolerance (HFI) is a potentially life-threatening disorder and can be suspected from a detailed nutritional history. The usefulness of 2 diagnostic procedures, fructose tolerance test (FTT) and aldolase assay on biopsied liver, was studied. A standardized intravenous FTT with 200 mg/kg b.w. was done on 11 children with HFI, 17 age-matched contrast children, 6 adults with HFI and 6 adult controls. Blood glucose, phosphorus, urate, magnesium and fructose were followed for 2 hours. By the FTT, each HFI individual was reliably distinguished from controls and contrasts and even from those with acute liver disease other than HFI. Both children with non-HFI hepatopathy examined by both procedures had a normal FTT in spite of reduced liver fructaldolase activity. HFI children responded to the FTT by earlier and more pronounced hypoglycemia than adults, and one girl converted to an adult type response between the ages 12 and 181/2 years. Responses of two HFI sibling pairs and of one set of monozygotic twins were typical for age, but resemblance was no greater than within the unrelated HFI probands. The intravenous FTT is judged a reliable diagnostic tool, simple and harmless if done in hospital. Essential fructosuria is readily diagnosed by the FTT, but fructose-1,6-diphosphatase deficiency and HFI are not differentiated with certainty. Liver biopsies were obtained from 35 children with HFI, 14 contrast persons and 10 controls (of which 9 organ donors) and examined enzymatically. Deficiency of fructaldolase was observed in all HFI children but also in some contrast children suffering from acute liver disease other than HFI. In these, HFI could only be excluded when the reduced activity of reference enzymes such as fructose-1,6-diphosphatase and glucose-6-phosphatase and liver histology were included in the evaluation. In one deceased HFI infant, fructaldolase was deficient in both, liver and kidney cortex. Extent of antibody activation and of heat inactivation of residual fructaldolase varied between unrelated HFI patients but not within families. These results did not contribute to diagnosis but further documented genetic heterogeneity of HFI. For diagnosis of HFI we recommend 1. immediate elimination of fructose from the diet, 2. the intravenous FTT after several weeks of fructose withdrawal, and 3., should diagnosis still be uncertain, laparoscopic liver biopsy for assay of fructaldose and of reference enzymes and for histology.
Helv Paediatr Acta 1981 Sep
PMID:The diagnosis of hereditary fructose intolerance. 626 73

The effects of phenol (P), dinitrophenol (DNP), pentachlorophenol (PCP), and their three combinations--(PCP + DNP)/P (highly antagonistic), (DNP + P)/PCP (additive) and (P + DNP)/PCP (highly synergistic)-- on glucose-6-phosphatase activity in liver, brain, kidney and gills of Notopterus notopterus were studied at three sub-acute concentrations (1/10, 1/15 and 1/20 the fraction of the 96-h LC50) after 15 and 30 days of exposure. When these chemicals were used separately, PCP exerted more effect than DNP and P. Maximum (71.56%) and highly significant (P less than 0.001) inhibition was observed in liver at the highest concentration of (P + DNP)/PCP combination after 30 days exposure, and lowest (3.64%) and insignificant inhibition in kidney at 1/20 of the (PCP + DNP)/P combination after 15 days exposure. Significant (P less than 0.05, P less than 0.01) stimulation in kidney or no effect in other tissues was observed in lower concentrations of P, DNP and (PCP + DNP)/P.
Toxicol Lett 1981 Sep
PMID:Effect of phenolic compounds on in vivo activity of glucose-6-phosphatase in certain tissues of Notopterus notopterus. 627 47

A previous report from this laboratory demonstrated age-related differences in the hormonal regulation of hepatic glucose-6-phosphatase (G-6-Pase). A detailed kinetic analysis of G-6-Pase activity has been performed to distinguish between effects on the microsomal carrier for glucose-6-phosphate and those on the enzyme itself. The maximum velocity (Vmax) was determined in untreated microsomes and microsomes treated with sodium deoxycholate (DOC); the Vmax of the enzyme (VE) was equal to the Vmax in the presence of DOC, and the Vmax of the carrier (VT) was calculated from the Vmax of untreated microsomes and the latency (the activity of DOC-treated microsomes not expressed by the intact preparation). The age-related decrease in G-6-Pase activity was caused by a decrease in the VE. In 3-month-old rats, the VE was increased 2,5-fold by treatment with T3, whereas triamcinolone or the two hormones in combination caused little effect; in 24-month-old animals, the VE was increased 10-fold by T3 and 2-fold by either triamcinolone or the two hormones in combination. In contrast, in 3-month-old animals, the VT was increased 2-fold by triamcinolone, 1.5-fold by T3, and 2-fold by the two hormones in combination; in 24-month-old animals, the VT was increased 3.5-fold by triamcinolone, was not affected by T3, and was increased 1.5-fold by the two hormones in combination. These differences could not be explained by changes in the response of isolated microsomes to sodium deoxycholate or by effects on the energy of activation of G-6-Pase. The results provide detailed evidence for an altered response to either T3 or triamcinolone in hepatocytes from old animals.
Endocrinology 1982 Sep
PMID:Age-related differences in the response of hepatic microsomal glucose-6-phosphatase to triiodothyronine and triamcinolone in the rat. 628 88

The addition of lipid peroxidation end-products, 4-hydroxynonenal (HNE) or hexanal (HEX) to the incubation medium of rat hepatocytes caused significant decrease of cell cytochrome P-450 content and inactivation of total cell glucose-6-phosphatase. Both the tested aldehydes exerted a marked inhibition of triglyceride secretion by liver cells. The reported results on intact cells furtherly support a possible damaging effect of aldehydes in pathological conditions in which a stimulation of lipid peroxidation occurs.
Boll Soc Ital Biol Sper 1982 Sep 30
PMID:Functional impairment of intact rat liver cells due to biological aldehydes. 629 59


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