Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It had previously been held that chlorate is not itself toxic, but is rendered toxic as a result of nitrate reductase-catalysed conversion to chlorite. This however cannot be the explanation of chlorate toxicity in Aspergillus nidulans, even though nitrate reductase is known to have chlorate reductase activity. Among other evidence against the classical theory for the mechanism of chlorate toxicity, is the finding that not all mutants lacking nitrate reductase are clorate resistant. Both chlorate-sensitive and resistant mutants lacking nitrate reductase, also lack chlorate reductase. Data is presented which implicates not only nitrate reductase but also the product of the nirA gene, a positive regulator gene for nitrate assimilation, in the mediation of chlorate toxicity. Alternative mechanisms for chlorate toxicity are considered. It is unlikely that chlorate toxicity results from the involvement of nitrate reductase and the nirA gene product in the regulation either of nitrite reductase, or of the pentose phosphate pathway. Although low pH has an effect similar to chlorate, chorate is not likely to be toxic because it lowers the pH; low pH and chlorate may instead have similar effects. A possible explanation for chlorate toxicity is that it mimics nitrate in mediating, via nitrate reductase and the nirA gene product, a shut-down of nitrogen catabolism. As chlorate cannot act as a nitrogen source, nitrogen starvation ensues.
Mol Gen Genet 1976 Jul 23
PMID:Chlorate toxicity in Aspergillus nidulans. Studies of mutants altered in nitrate assimilation. 0 97

The lower Vmax of 6PGDH with respect to G6PDH and its higher sensitivity to inhibition by NADPH, suggest the existence of an imbalance between the two dehydrogenases of the pentose phosphate pathway in rat liver. Possible modulators of these activities, particularly in relation with the inhibition by NADPH in physiological conditions, have been investigated. The results suggest that in both cases the inhibition by NADPH is strictly isosteric and that the relative affinities for the reduced and oxidized forms of the pyridine nucleotide are unaffected by glutathion, the intermediates of the pentose phosphate shunt or some divalent ions.
Mol Cell Biochem 1977 Oct 07
PMID:Effectors of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase of rat liver. 2 33

Thyroid hormones regulate lipid metabolism by affecting lipogenesis as well as lipolysis. The present paper discusses the way thyroidectomy induced an enhancement in lipogenesis in rat fat cells. The doubling in the conversion of glucose to CO2 and fatty acids seen after thyroidectomy was found to be due to a modification in the actual pathway of glucose metabolism: there was a preferential stimulation of the conversion of glucose to CO2 by the pentose cycle (utilisation of [1-14C]glucose) while the production of fatty acids and glyceride-glycerol proceeded, respectively, much more, or only slightly more, via the pathway of [6-14C]glucose metabolism. Studies employing the phosphodiesterase inhibitor MIX, or the cyclic AMP analogue, DBcAMP showed that the lipogenic process depends on cyclic AMP. As the stimulatory effect of thyroidectomy was not abolished, however, lipogenesis must be under the independent control of both cyclic AMP and absence of thyroid hormones. Insulin, a further mediator of lipogenesis was found to further enhance the already preexisting high conversion of glucose to CO2 in fat cells from thyroidectomized rats. It is concluded that at least three factors modify lipogenesis: thyroidectomy, cyclic AMP and insulin; each achieving its effect in an independent manner.
Mol Cell Endocrinol 1979 Jun
PMID:Cyclic AMP and lipogenesis in fat cells from thyroidectomized rats. 8 52

1. Hypoxanthine--guanine phosphoribosyltransferase (HGPRT) activity was measured in erythrocyte haemolysates and quadriceps muscle extracts of normal and dystrophic 129 ReJ and C57 BL/6J mice with [8(-14)C]hypoxanthine as substrate and 5-phosphorylribose 1-pyrophosphate as a ribose 5-phosphate donor. [8(-14)C]Inosine monophosphate formed was separated by high-voltage electrophoresis and radioactivity was measured by liquid-scintillation counting. 2. In erythrocyte haemolysates, HGPRT activity was similar in normal and dystrophic C57 BL/6J mice but was significantly higher in dystrophic than in normal 129 ReJ mice. Elevated enzyme activity was observed only in mice that were clinically severely affected. 3. In muscle homogenates, HGPRT activity was significantly higher in dystrophic than in normal animals of both 129 ReJ and C57 BL/6J mice. Enzyme activity was not related to the severity of the disease. 4. It is suggested that changes in erythrocytes are secondary to the dystrophic process and that elevated HGPRT activity in skeletal muscle may be related to abnormal energy metabolism, possibly via the pentose monophosphate shunt.
Clin Sci Mol Med Suppl 1978 Dec
PMID:Hypoxanthine--guanine phosphoribosyltransferase activity in blood and skeletal muscles of normal and dystrophic mice. 28 49

Mutants of Klebsiella aerogenes W70 that metabolize the uncommon pentose D-arabinose were isolated. These mutants were found to be either constitutive or indicible by D-arabinose for the synthesis of enzymes in the L-fucose pathway. Such mutants could then utilize L-fucose isomerase to convert the structurally similar D-arabinose molecule to D-ribulose. D-Ribulose is an intermediate and the inducer of an existing ribitol pathway and could thus be metabolized. In those D-arabinose-positive mutants where the ribitol pathway was blocked by mutation, D-ribulose could alternatively be metabolized by using the remaining L-fucose pathway enzymes. When the two D-arabinose catabolic routes were compared, catabolism of D-arabinose via the ribitol pathway was found to be more efficient. Catabolism of D-arabinose using the L-fucose pathway permitted D-ribulose to escape into the media and produced an unmetabolizable end product, L-glycolic acid. A comparison of growth using constitutive versus inducible control of the borrowed L-fucose isomerase did not reveal an advantage for one control type over the other. Several differences were observed, however, when we determined the degree to which these control mutations perturbed the normal functioning of the L-fucose and associated pathways. Growth of the constitutive mutant was impaired with L-fucose as substrate. The inducible-control mutant had altered growth characteristics on ribitol and L-rhamnose.
J Mol Evol 1977 Nov 25
PMID:A comparison of alternate metabolic strategies for the utilization of D-arabinose. 33 26

Cobalt, a metal with numerous industrial applications, has been associated with lung disease, an extreme form of which is an interstitial fibrosis. The biochemical mechanisms underlying this toxicity are not understood. In vitro studies have suggested that cobalt(II) ions are able to generate reactive oxidant species (possibly hydroxyl radical) in a reaction with hydrogen peroxide, and we have hypothesized that the occurrence of such an event in lung tissue, and the subsequent development of oxidative damage, may contribute to this pulmonary toxicity. The intratracheal instillation of CoCl2 into hamster lungs resulted after 3 h in decreased levels of reduced glutathione and increases in levels of oxidized glutathione and in the activity of the pentose phosphate pathway. These changes, which are compatible with the generation of oxidative stress, were reversed by 48 h at low Co2+ doses (1.0 to 1,000 micrograms/kg). Irreversible changes at higher doses coincided with the onset of pulmonary edema. Incubation of lung slices with CoCl2 (0.1 to 10 mM) resulted in time- and Co2+ concentration-dependent increases in levels of oxidized glutathione and protein-mixed disulfides and a decrease in reduced glutathione. A concentration-dependent stimulation of the pentose phosphate pathway was also observed. These changes preceded the detection of overt cell toxicity, as assessed by various biochemical parameters. These data indicate that thiol oxidation constitutes an early event in the pulmonary toxicity of cobalt(II) ions and are compatible with the hypothesis that the generation of oxidative stress may be of significance to the toxic process.
Am J Respir Cell Mol Biol 1991 Aug
PMID:Indices of oxidative stress in hamster lung following exposure to cobalt(II) ions: in vivo and in vitro studies. 189 47

Oxidative stress induced by cumene hydroperoxide was studied in cultured neonatal rat myocytes. A progressive increase of irreversible cell injury as determined by leakage of the cytoplastic enzyme alpha-hydroxybutyrate dehydrogenase (alpha-HBDH) from the cells was noted at concentrations ranging from 25-100 microM cumene hydroperoxide (incubation time 90 min). Cumene hydroperoxide-induced damage was reduced or prevented by several compounds: the application of Trolox C, a water-soluble vitamin E analogue, and of phospholipase A2 inhibitors chlorpromazine and (to a lesser extent) quinacrine prevented alpha-HBDH release. ICRF-159, a chelator of divalent cations, ascorbic acid, a potent antioxidant, and the cysteine protease inhibitor leupeptin did not reduce the cumene hydroperoxide-induced cytotoxicity. Detoxification of hydroperoxides by the glutathione peroxidase system results in an increased flux through the pentose phosphate shunt and loss of NADPH. Glucose inhibited the cumene hydroperoxide-induced alpha-HBDH release, probably by replenishing NADPH. These results indicate that cumene hydroperoxide, after exhaustion of the glutathione system, induces irreversible injury in cultured myocytes by a mechanism that depends to a large extent on deterioration of cellular membranes caused by lipid peroxidation and phospholipase activation.
J Mol Cell Cardiol 1990 Oct
PMID:Prevention of cumene hydroperoxide induced oxidative stress in cultured neonatal rat myocytes by scavengers and enzyme inhibitors. 209 37

Immature female rats (23-30 days old) were implanted subcutaneously with diethylstilbestrol (DES) in silastic capsules. After 48 h their ovaries were removed and the granulosa cells isolated (Foreman et al. (1984) Life Sci. 35, 1273-1279). The cells were incubated in Hepes balanced saline buffer with substrates with or without follicle-stimulating hormone (FSH). At the end of incubation perchloric acid extracts were made for 31P NMR spectroscopy. The resonances of fructose 1-phosphate, fructose 6-phosphate, glucose 1-phosphate, and ribose 5-phosphate were identified in the granulosa cell extracts. The relative intensities of fructose 6-phosphate to ribose 5-phosphate decreased after incubation with FSH in vitro. This suggests that FSH increases the activity of the pentose pathway within 1 h. Thus, FSH can acutely activate those metabolic pathways which provide nicotinamide-adenine dinucleotide phosphate (NADPH) to be used in steroid synthesis and cholesterol mobilization.
Mol Cell Endocrinol 1990 Oct 22
PMID:31P nuclear magnetic resonance (NMR) identification of sugar phosphates in isolated rat ovarian follicular granulosa cells and the effects of follicle-stimulating hormone. 212 82

Neonatal and adult rat islets, cultured for 7-9 days in the presence of 10.5 mM D-glucose, were incubated for 120 min with either D-glucose (2.8 and 16.7 mM) or L-leucine (1.0 and 20.0 mM). The total and anaerobic rates of glycolysis, as judged respectively through the generation of 3H2O from D-[5-3H]glucose and 14C-labelled lactate from D-[3,4-14C]glucose or D-[6-14C]glucose were higher in neonatal than adult islets, but increased to a lesser relative extent in neonatal than adult islets in response to a rise in hexose concentration. The flow through the pentose phosphate pathway, as judged from the difference between D-[1-14C]glucose and D-[6-14C]glucose oxidation was higher in neonatal than adult islets. The flow through the reaction catalyzed by pyruvate dehydrogenase, as judged from the oxidation of D-[3,4-14C]glucose, was lower in neonatal than adult islets incubated in the presence of 16.7 mM (but not 2.8 mM) D-glucose. The oxidation of acetyl residues relative to their generation rate, as judged from the ratio of D-[6-14C]glucose to D-[3,4-14C]glucose oxidation, was not affected by the hexose concentration whether in neonatal or adult islets, but was about twice higher in the latter than former islets. The rate of D-[6-14C]glucose oxidation was also higher in adult than neonatal islets, especially at the high concentration of D-glucose. In both neonatal and adult islets, a rise in hexose concentration stimulated preferentially the oxidation of D[3,4-14C]glucose or D-[6-14C]glucose relative to the utilization of D-[5-3H]glucose.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Endocrinol 1990 Oct 01
PMID:D-glucose and L-leucine metabolism in neonatal and adult cultured rat pancreatic islets. 229 40

Prolactin deficiency, induced by bromocryptine treatment, brought about reciprocal changes in the ability of adipocytes and acini isolated from lactating rats to synthesize lipids. The capacity to synthesize fatty acids and phospholipids decreased in the mammary gland and increased in adipocytes by bromocryptine treatment. In the mammary gland, the maximum potential activity of the pentose shunt as well as the specific activities of the pathway dehydrogenases were significantly reduced by bromocryptine treatment. Simultaneously, adipose tissue increased its lipogenic capacity but neither the maximum potential of the shunt nor the specific activities of the pentose phosphate shunt dehydrogenases were significantly changed with respect to the control lactating rats. Thus, a differential regulatory mechanism(s) of the pentose phosphate shunt activity appears to operate in these two tissues. Adipocytes from lactating rats showed a poor responsiveness to insulin in terms of lipid synthesis from glucose. In contrast, in adipocytes from bromocryptine treated rats insulin was able to increase lipid synthesis (105%). Sheep prolactin administration 'in vivo' partially reversed the effects of bromocryptine. These data suggest that prolactin mediates adipocytes resistance to insulin during lactation. Phospholipid synthesis, as occurred in fatty acid synthesis, is increased in adipose tissue and decreased in mammary gland by bromocryptine treatment. However, alpha 1-adrenergic stimulation increases phosphatidylinositol turnover to about the same percentages in both mammary gland acini and adipocytes from lactating rats independently of bromocryptine treatment.
Mol Cell Biochem 1990 Mar 27
PMID:Integration of lipid metabolism in the mammary gland and adipose tissue by prolactin during lactation. 234 43


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