Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.5.1.3 (dihydrofolate reductase)
 5,819 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The amount of xanthine dehydrogenase (XDH), dihydrofolate reductase (DHFR), and lactate dehydrogenase (LDH) in crude extracts of 4- to 5-day-old adult Aedes aegypti was determined, and the properties of these enzymes were partially characterized. It was then found that the amount and other selected characteristics of XDH and LDH in extracts of female Ae. aegypti processed 5 to 7 days and 12 to 14 days after they had fed upon either normal or Brugia pahangi-infected jirds were indistinguishable from those of these two enzymes in extracts of female mosquitoes that did not have a blood meal. Under the same circumstances, the selected characteristics of DHFR were also unaffected. However, there was a suggestion that the amount of DHFR was slightly increased in extracts of female Ae. aegypti processed 5 to 7 days after they had fed upon B. pahangi-infected jirds; by 12 to 14 days after the blood meal, there was a consistent 30% to 60% increase in the amount of DHFR inextracts of infected mosquitoes. DHFR activity could not be detected in a similarly prepared extract of 4,000 to 5,000 infective (L-3) B. pagangi larvae, the approximate number present in the infected mosquito extracts. It would appear, therefore, that the increased amount of turnover of DHFR in the mosquito host occurs in response to advanced infection with B. pahangi.
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PMID:Comparative activity and properties of lactate dehydrogenase, xanthine dehydrogenase, and dihydrofolate reductase in normal and Brugia pagangi-infected Aedes aegypti. 55 68

The activities of glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate: NADP oxidoreductase, G6PD), 6-phosphogluconate dehydrogenase (6-phospho-D-gluconate: NADP oxidoreductase, 6PGD), hexokinase (ATP: D-hexose 6-phosphotransferase, Hx), lactate dehydrogenase (D-lactate: NAD oxidoreductase, LDH). glutamate oxaloacetate transaminase (L-aspartate: 2 oxoglutarate aminotransferase, GOT) and dihydrofolate reductase (DHFR) were measured at 8 a.m. in leucocytes of healthy individuals and patients with chronic myeloid leukaemia (CML), chronic lymphatic leukaemia (CLL), myelofibrosis with myeloid metaplasia and polycythaemia vera. In view of the heterogeneity of the leucocyte populations in these conditions, the enzyme activities were correlated to the number of immature cells in CML and to the percentage of lymphocytes in CLL. No differences in the enzyme activities were found between the white cells of healthy individuals, myelofibrosis with myeloid metaplasia and polycythaemia vera. In CML the activities of all enzymes except GOT correlated directly with the number of immature cells; an inverse correlation with the number of lymphocytes was observed in CLL. GOT was the only enzyme whose activity correlated with the number of lymphocytes in the cell suspension. Furthermore, a significantly higher activity of this enzyme was found in Ficoll-isolated CLL lymphocytes as compared to normal lymphocytes.
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PMID:Blood leucocyte enzymes. II. Activities at 8-9 a.m. in cells of normal subjects, chronic lymphatic leukaemia and chronic myeloid leukaemia patients. 105 70

gamma-Glutamyl hydrolase (also known as conjugase) is a ubiquitous enzyme that has the capacity to cleave folyl- and antifolylpolyglutamates. This study has revealed that the enzyme is secreted by primary cultures of rat hepatocytes and by H35 hepatoma cells. H35 cells have lower cellular levels of gamma-glutamyl hydrolase than do hepatocytes but secrete a greater proportion of gamma-glutamyl hydrolase. More than 99% of the total enzyme from H35 cells accumulated in the medium after 48 h. The cells were shown to remain intact during the secretion period since lactate dehydrogenase, dihydrofolate reductase, and lysosomal hydrolases other than gamma-glutamyl hydrolase were retained within the cell. Using the substrate 4-amino-10-methyl-pteroyldiglutamate (4-NH2-10-CH3-Pte-Glu2), the intracellular and secreted enzyme form(s) from H35 cells were found to have the following properties (a) Km values of 24.3 +/- 3.7 microM and 34.8 +/- 8.6 microM, respectively, and (b) maximal activity at pH 5 to 7 and apparent molecular weights of 120,000 by gel filtration. Both the cellular and secreted enzymes convert 4-NH2-10-CH3-PteGlu4 and pteroylpentaglutamate acid, to the corresponding monoglutamates with little or no appearance of intermediate chain length polyglutamates. This suggests that both act primarily as endopeptidases. Thus far, the cellular and secreted enzymes cannot be differentiated although the current studies do not establish this point unequivocally. Alterations in the cellular and secreted H35 cell gamma-glutamyl hydrolase levels in response to changes in culture conditions revealed that glutamine enhances activity while insulin diminishes it. Other transformed cells found to secrete this protein are Hep-G2 human hepatoma, JAR human choriocarcinoma, HeLa, and rat glioma. gamma-Glutamyl hydrolase could not be detected in medium conditioned by human MCF-7 breast cancer cells, and relatively low activities were found in the medium from CCRF-CEM or K562 leukemia cells. These studies directly establish for the first time the secretion of gamma-glutamyl hydrolase in vitro.
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PMID:Secretion of gamma-glutamyl hydrolase in vitro. 171 22

Effect of vasopressin, oxytocin and LHRH (10 and 20 pg/ml medium) on the proliferation and metabolism of cultured rat bone marrow stromal cells was investigated by methyl-3H-thymidine incorporation, cytochemistry and estimation of enzyme activities. Vasopressin did not change of the activity of tetrahydrofolate dehydrogenase (4HFDH), lactate dehydrogenase (LDH), glucose-6-phosphate dehydrogenase (G6PD) and the level of reduced glutathione (GSH). However, the higher concentration of vasopressin significantly lowered the activity of acetylcholinesterase (AchE). As compared with the control cultures, stromal cells grown in the presence of oxytocin showed higher (at lower hormone concentration) and lower (at higher concentration) LDH activity as well as lower G6PD activity (only at higher concentration), while the activity of AchE and the level of GSH was not changed. LHRH significantly increased G6PD and AchE activity and decreased LDH activity in the cultured cells. As revealed by cytochemistry, LHRH specifically enhanced 4HFDH activity in reticular cells.
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PMID:Effect of vasopressin, oxytocin and LHRH on the proliferation and metabolism of rat bone marrow stromal cells in culture. 176 8

In an attempt to clarify the role of beta interferon in vitro cell systems, the metabolic expression of dihydrofolate reductase (DHFR), succinate dehydrogenase (SDH) and lactate dehydrogenase (LDH), by histochemical methods was studied. DHFR was also quantified by flow cytometry. Glioblastoma cell line with or without beta interferon was used. Three days after the treatment the DHFR reaction was much less intense than in the control. Quantitative data confirmed these results. Immediately afterwards, most cells exhibited much more intense reaction. These facts underlined that, in this biological model in vitro, beta interferon could reduce the synthesis of these enzymes only for a short period.
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PMID:[Qualitative and quantitative histochemical evaluation of the dehydrogenase activity in human glioblastoma cells treated with beta-interferon]. 237 36

The different distribution of cytochemically demonstrable enzymes: lactate dehydrogenase (LDH, 1.1.1.27), succinate dehydrogenase (SDH, 1.3.99.1), dihydrofolate reductase (DHFR, 1.5.1.3), acid phosphatase (AcP, 3.1.3.2) and alkaline phosphatase (ALP, 3.1.3.1), has been documented in Yoshida ascites hepatoma cells in vivo or stored at 80 degrees C. The dehydrogenase activities (LDH, SDH, DHFR) show a strong reaction in all samples. An increased level of these enzyme activities has been observed in the malignant cells spreading through the organs of tumor bearing rats. On the contrary, in the same samples, acid and alkaline phosphatase activities are very low. The strong dehydrogenase activities observed in Yoshida ascite cells stress the rapid turnover of tumor cells. Our results indicate that the histochemical method may be a useful tool to detect the scattered tumor cells. Furthermore, the cytochemical methods allow the characterization of the metabolic pathways employed by the primary and disseminated tumor cells.
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PMID:[Cytochemical study of cells of primary and disseminated ascite Yoshida tumor cells]. 276 51

gamma-Glutamyl hydrolase is a ubiquitous enzyme that has the capacity to cleave gamma-glutamyl bonds of cellular folyl- and antifolylpoly-gamma-glutamates. This study has revealed that the enzyme is secreted by primary cultures of rat hepatocytes and by H35 hepatoma cells. It was found that more than 99% of the total enzyme from H35 cells accumulated in the medium after 48 hr incubation with the serum-free medium. The cells were shown to remain intact during the secretion period since lactate dehydrogenase, dihydrofolate reductase and lysosomal hydrolases other than gamma-glutamyl hydrolase were retained within the cell. When PteGlu5 (folylGlu4) is used as a substrate the initial product is PteGlu (folate), and there is no appearance of intermediate chain length pteroyl polyglutamates. Therefore, the secreted and cellular gamma-glutamyl hydrolase from hepatoma cells appears to be an endopeptidase. Polyclonal antibodies to the poly-gamma-glutamate substrates of the enzyme were prepared and characterized. The antibodies recognize the structural differences between alpha- and gamma-glutamyl linkages but appear equally active with PteGlu5 and its analogs such as 4-NH2-10-CH3PteGlu5 and pABAGlu5. The affinity of the antibodies is related to the gamma-glutamyl structure since L-glutamic acid, folate or p-aminobenzoic acid are inactive with the antibodies. Furthermore, poly-gamma-glutamate has lower affinity for the antibodies than the poly-gamma-glutamate derivatives of PteGlu, 4-NH2-10-CH3PteGlu or pABA.
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PMID:The properties and function of gamma-glutamyl hydrolase and poly-gamma-glutamate. 768 89

It has been shown in this and other laboratories that during the unfolding of a number of enzymes inactivation generally precedes global unfolding of the enzyme molecule, leading to the suggestion that enzyme active sites are usually more "fragile" and more easily "perturbed" than the molecule as a whole and are therefore conformationally more flexible than the rest of the molecule. However, the role of active site flexibility in enzyme catalysis still remains to be explored. In the induced fit hypothesis originally proposed by Koshland, the presence of the substrate induces a conformational change at the active site so as to fit with the structure of the substrate. By X-ray crystallographic structural analysis of E. coli dihydrofolate reductase liganded with cofactors and substrates, Sawaya and Kraut showed the enzyme in different conformational states indeed while complexed with different ligands, suggesting that the enzyme molecule passes through different conformational states through the whole process of catalysis. Muscle lactate dehydrogenase can be stabilized either in concentrated ammonium sulfate or by cross-linking with glutaraldehyde together with a decrease in enzyme activity which can be restored to the original level in dilute guanidine hydrochloride possibly by increased flexibility at the active site. It is known that a number of enzymes can be activated by chaotropic agents such as urea or guanidine hydrochloride. The activation of dihydrofolate reductase by either urea or guanidine hydrochloride is accompanied by an increase in susceptibility to proteolysis. Isolation of the tryptic peptides of the activated enzyme and sequence analysis allowed identification of the sites of proteolysis to be at or near the active site of the enzyme, indicating an opening up of the active site conformation in the activated state. All the above indicate that active site flexibility plays an important role in enzyme catalysis. It is possible that during the catalytic cycle, the enzyme molecule passes through different stages and each stage requires the molecule to be in a different conformation, especially at the active site. Rapid transition between the different conformational states, and hence the flexibility of the active site, is therefore mandatory for the maximal expression of enzyme activity.
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PMID:The role of active site flexibility in enzyme catalysis. 952 22

The effect of alteration of the glycolytic pathway on cell damage induced by oxidative stress was investigated with dihydrofolate reductase-deficient Chinese hamster ovary (CHO) cells that either overexpress cytosolic glycerol-3-phosphate dehydrogenase (CHO/cGPDH cells) or are depleted of the A subunit of lactate dehydrogenase as a result of anti-sense RNA expression (CHO/anti-LDH cells). The extent of oxidative phosphorylation in CHO/anti-LDH and CHO/cGPDH cells was increased and decreased, respectively, relative to that in parental CHO cells, as revealed by measurement of the intracellular content of ATP, the rate of cellular O(2) consumption, the mitochondrial membrane potential (DeltaPsi(m)), and the generation of reactive oxygen species. The sensitivity of these cell lines to cell death induced by the exogenous oxidant tert-butyl hydroperoxide decreased according to the rank order CHO/anti-LDH>CHO>CHO/cGPDH. Exogenous pyruvate markedly increased the sensitivity of CHO/cGPDH cells to oxidant-induced death. The differences among the three cell lines in susceptibility to oxidant-induced death were reflected in the proportion of oxidant-treated cells with a subdiploid DNA content, with a collapsed DeltaPsi(m), and with cytochrome c in the cytosol, indicating that death was mediated by apoptosis. These results demonstrate that the influx of respiratory substrate into mitochondria is an important determinant of cell sensitivity to oxidant-induced apoptosis.
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PMID:Modification of glycolysis affects cell sensitivity to apoptosis induced by oxidative stress and mediated by mitochondria. 1470 39

Malaria remains a major disease of mankind, and resistance to existing therapeutics is rapidly emerging. Limited financial investment to develop new therapeutics requires the careful selection of well-defined targets from the causative parasite, Plasmodium falciparum. In these circumstances, protein crystallography can provide valuable structural detail to facilitate both the selection of suitable targets and the development of compounds to provide novel drug candidates. This review summarises the current involvement of crystallographic studies in anti-malarial drug development programmes. Protein crystallography is increasingly central to the exploitation of a number of potential Plasmodial targets. including the aspartic acid proteases (plasmepsins) and cysteine proteases (falcipains) involved in haem degradation within the parasite food vacuole. Lead compounds are being identified from collections previously synthesised against homologous human enzymes. Plasmodium have an unusual dependence on the glycolytic pathway relative to their human hosts, and this is reflected in subtle structural differences identified in the crystal structures of a number of parasite glycolytic enzymes including aldolase and lactate dehydrogenase. Other enzymes from a range of biosynthetic pathways have also been targeted in crystallographic studies. These include dihydrofolate reductase, the target of existing anti-folate therapeutics, and enoyl reductase from the fatty acid biosynthesis pathway which is already the target of effective bacteriocides. Crystal structures of these drug-enzyme complexes not only allow visualisation and improvement of inhibitor-protein contacts, but in the former case have also been used to probe the molecular basis of emerging anti-malarial drug resistance. Crystallography is similarly proving valuable as a tool to facilitate the development of inhibitors of purine salvage, isoprenoid synthesis and utilisation, and protein processing mechanisms.
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PMID:Structure-based approaches to the development of novel anti-malarials. 1501 47


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