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:3.1.3.5 (5'-nucleotidase)
3,167 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Incubation of Schistosoma mansoni for 5 min in a phosphate-buffered medium, pH 7.4, released tegumental material containing the following phosphohydrolase activities: alkaline phosphatase, 5'-nucleotidase, glycerol-2-phosphatase, glucose 6-phosphatase, phosphodiesterase and ATPase. 2. Maximum activity of these enzymes was measured at pH 9.5; however, the phosphodiesterase and ATPase activities were also appreciable at pH 7.0. 3. Solubilization of the released tegumental material in 1% Triton X-100 followed by gel filtration distinguished three peaks of enzyme activity: an ATPase (mol.wt. greater than 1000 000), a phosphodiesterase (mol.wt. 1 000 000) and an alkaline phosphomonoesterase with broad specificity (mol.wt. 232 000). 4. The ATPase activity was highly activated by 10 mM-Mg2+ or 1 mM-Ca2+ and was inhibited by chelating agents. Ouabain, Na+ and K+ had little effect on enzyme activity, whereas activity was increased by 50% in the presence of calmodulin. The phosphodiesterase activity was highest in the presence of 100 mM-Na+ or -K+, and 10 mM-Mg2+ or -Ca2+. Alkaline phosphatase activity was also stimulated by 100 mM-Na+ or -K+, and 10 mM-Mg2+; however Ca2+ inhibited at greater than 1 mM. 5. Surface iodination of parasites followed by detergent solubilization and gel filtration of the released tegumental membranes indicated that these enzymes were not accessible. A major surface component, apparent mol.wt. 80 000, was iodinated. 6. Rabbit anti-(mouse liver 5'-nucleotidase) antibodies did not inhibit the phosphohydrolase activities. However, an immunoglobulin G fraction from sera of mice chronically infected with S. mansoni partially inhibited alkaline phosphatase activity, but was without effect on the phosphodiesterase and ATPase activities. 7. The location of the enzymes in the double membrane of the tegument and their significance in host-parasite interactions is discussed.
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PMID:Properties of a series of tegumental membrane-bound phosphohydrolase activities of Schistosoma mansoni. 627 49

We evaluated the erythrocytes of two patients with hereditary pyrimidine 5'-nucleotidase deficiency. Significant findings included an increased reduced glutathione content, increased incubated Heinz body formation, a positive ascorbate cyanide test, and decreased intraerythrocytic pH. The pentose phosphate shunt activity of the patients' red cells as measured by the release of 14CO2 from 14C-1-glucose was decreased compared to high reticulocyte controls. Glucose-6-phosphate dehydrogenase (G6PD) activity in hemolysates from control erythrocytes was inhibited 43% by 5.5 mM cytidine 5'-triphosphate (CTP) and 50% by 5.5 mM in uridine 5'-triphosphate (UTP) at pH 7.1. CTP was a competitive inhibitor for G6P (Ki = 1.7 mM) and a noncompetitive inhibitor for NADP+ (Ki = 7.8 mM). Glutathione peroxidase, glutathione reductase, and 6-phosphogluconate dehydrogenase were not affected by these compounds. Pentose phosphate shunt activity in control red cell hemolysate at pH 7.1 was inhibited to a similar degree by 5.5 mM CTP or UTP. Since the intracellular concentrations of G6P and NADP+ are below their KmS for G6PD, these data suggest that high concentrations of pyrimidine 5'-nucleotides depress pentose phosphate shunt activity in pyrimidin 5'-nucleotidase deficiency. Thus, this impairment of the pentose phosphate pathway appears to contribute to the pathogenesis of hemolysis in pyrimidine 5'-nucleotidase deficiency hemolytic anemia.
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PMID:Hemolytic anemia in hereditary pyrimidine 5'-nucleotidase deficiency: nucleotide inhibition of G6PD and the pentose phosphate shunt. 628 44

Induction studies on pyrimidine metabolizing enzymes in E. coli B have shown that the enzymes fall into three distinct groups according to their induction pattern. a) Cytidine deaminase and uridine phosphorylase, are induced by cytidine, CMP and adenosine; no induction was observed with uridine and AMP; b) thymidine phosphorylase is induced by cytidine, adenosine, all deoxyribonucleosides, CMP, deoxyribonucleotides, deoxyribose and deoxyribose-1-phosphate; c) uridine-cytidine kinase, uracil phosphoribosyltransferase, 5'-nucleotidase, thymidine kinase, are uninducible enzymes. Simultaneous addition of cytidine and glucose partially overcomes the cytidine deaminase and uridine phosphorylase induction. Cytidine deaminase reaches its maximum activity levels, in E. coli growing cells in presence of cytidine, two hours before the uridine phosphorylase activity. Maximum glucose repression of cytidine deaminase and uridine phosphorylase was obtained in correspondence of maximum cytidine induction.
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PMID:Induction of pyrimidine nucleoside metabolizing enzymes in E. coli B. 636 Sep 49

The mechanism of insulin action on glucose transport in rat hearts was studied. The glucose transport activity was determined after reconstitution into egg lecithin liposomes. Isolated rat hearts were perfused in the presence or absence of insulin and homogenized. The homogenate was fractionated by differential and sucrose density gradient centrifugations. Two subcellular fractions, designated as Fractions P-5 and P-6, contained glucose transport activity. Both fractions were enriched with 5'-nucleotidase (commonly known as a plasma membrane marker) and UDP-Gal:N-acetylglucosamine galactosyltransferase (known as a Golgi marker). However, only Fraction P-5 was concentrated with the insulin receptor and ouabain-sensitive p-nitrophenylphosphatase (both plasma membrane markers). The sedimentation properties of the glucose transport activity in Fraction P-6 were considerably different from those of galactosyltransferase. Insulin added to the heart before homogenization increased the glucose transport activity in Fraction P-5 approximately 1.6-fold while decreasing the activity in Fraction P-6 to approximately 62% of the control. These results are interpreted as follows. Both Fractions P-5 and P-6 are heterogeneous; nevertheless, Fraction P-5, but not Fraction P-6, may be enriched with the plasma membrane, which is assumed to be associated with glucose transport activity. Fraction P-6 may be concentrated with the Golgi apparatus; however, the latter may not be the structure (or vesicles) to which (intracellular) glucose transport activity is associated. Insulin appears to increase the glucose transport activity in rat hearts, at least in part, by inducing translocation of the glucose transport mechanism from the unidentified vesicles (in Fraction P-6) to the plasma membrane (in Fraction P-5).
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PMID:Insulin action on glucose transport in cardiac muscle. 638 8

A technique employing sucrose-density centrifugation for the enrichment of rat liver microsomes and rat liver plasma membranes in separate subcellular fractions is described. The fractions are enriched in glucose 6-phosphatase and 5'-nucleotidase, respectively, and are free of cytochrome oxidase activity. Vanadate-sensitive Ca2+ transport activity (half-maximal inhibition at approximately 10 microM vanadate, corresponding to approximately 12 nmol/mg of protein) was detected in only that fraction enriched in microsomal membranes. Inhibition by vanadate of ATP-dependent Ca2+ transport is noncompetitive with respect to added Ca2+ but competitive with respect to added ATP. Because it inhibits ATP-dependent Ca2+ transport in rat liver microsomes but not in rat liver plasma membranes, vanadate becomes a useful tool to distinguish in vitro between these two transport systems.
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PMID:Inhibition by orthovanadate of ATP-dependent Ca2+ transport in microsomes isolated from rat liver. 656 71

The glucose transport activity of fat cells was assayed in a cell-free system. The activity was solubilized and incorporated into egg-lecithin liposomes. The carrier-mediated glucose transport activity was estimated by subtracting the cytochalasin B-insensitive component from the total glucose uptake activity of the modified liposomes. When a crude microsomal preparation from fat cells was fractionated by sucrose density gradient centrifugation, two transport activities (peaks A and B) were separated. Peak A coincided with the peak of 5'-nucleotidase, a marker of the plasma membrane. Peak B appeared to coincide with the peak of UDPGal:N-acetylglucosamine galactosyltransferase, a marker of the Golgi apparatus. Peak A was considerably smaller than peak B under basal conditions. When cells were exposed to 1 nM insulin for 5 min before homogenization, the height of peak A increased whereas that of peak B decreased. Insulin had no significant effect on the galactosyltransferase activity. The Km values of glucose transport facilitated by the activities in peaks A and B were both approximately 10-15 mM. These results imply that insulin facilitates translocation of the transport activity from an intracellular storage site to the plasma membrane.
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PMID:Evidence that insulin causes translocation of glucose transport activity to the plasma membrane from an intracellular storage site. 677 56

The glucose transport mechanism of rat epididymal fat cells was reconstituted into egg lecithin liposomes, and their carrier-mediated transport activity ws estimated from the difference in the rates of uptake of D-[3H]glucose and L-[14C]glucose. Insulin increased the glucose transport activity in the plasma membrane-rich fraction while decreasing the activity in the Golgi-rich fraction in agreement with our previous data (Suzuki, K., and Kono, T. (1980) Proc. Natl. Acad. Sci. U. S. A. 77, 2542-2545). The development of the insulin effects was inhibited when cells were exposed to 2,4-dinitrophenol or KCN before the insulin treatment. In addition, the reversal of the insulin effects was blocked upon exposure of insulin-treated cells to 2,4-dinitrophenol or KCN prior to the elimination of the hormone. In contrast, neither development nor reversal of the insulin effects was affected by cycloheximide or puromycin. The temperature coefficients of the transport activities reconstituted from the basal or insulin-treated forms of the plasma membrane-rich or Golgi-rich fractions were all identical. The recoveries of protein, 5'-nucleotidase, UDP-galactose:N-acetylglucosamine galactosyltransferase, and NADH dehydrogenase into subcellular fractions were determined. However, net effects of insulin on the glucose transport activities have remained unknown for lack of an appropriate marker enzyme of the Golgi-like vesicles associated with the transport activity. It is suggested that the glucose transport mechanism is recycled between the plasma membrane-rich and Golgi-rich fractions by an energy-dependent reaction.
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PMID:Energy-dependent and protein synthesis-independent recycling of the insulin-sensitive glucose transport mechanism in fat cells. 701 68

Sulphonylurea drugs stimulate glucose transport and metabolism in muscle and fat cells in vitro. The molecular basis for the insulin-mimetic extrapancreatic effects of these oral antidiabetic therapeutic agents is unknown at present. Here we demonstrate that incubation of 3T3 adipocytes with the novel sulphonylurea, glimepiride, causes a time- and concentration-dependent release of the glycosylphosphatidylinositol (GPI)-anchored ecto-proteins, 5'-nucleotidase, lipoprotein lipase and a 62 kDa cyclic AMP (cAMP)-binding protein from the plasma membrane into the culture medium. The change in the localization is accompanied by conversion of the membrane-anchored amphiphilic proteins into their soluble hydrophilic versions, as judged by pulse-chase experiments and Triton X-114 partitioning, and by appearance of anti-cross-reacting determinant (CRD) immunoreactivity of the released proteins as shown by Western blotting. Metabolic labelling of cells with myo-[14C]inositol demonstrates that inositol is retained in the major portion of released lipoprotein lipase and cAMP-binding ectoprotein. The identification of inositol phosphate after deamination of these proteins with nitrous acid suggests cleavage of their GPI membrane anchor by a GPI-specific phospholipase C. However, after longer incubation with glimepiride the amount of soluble versions of the GPI-proteins lacking inositol and anti-CRD immunoreactivity increases, which may be caused by additional drug-stimulated hydrolytic events within their GPI structure or C-termini. Since insulin also stimulates membrane release of these GPI-modified proteins, and in combination with glimepiride in a synergistic manner, sulphonylurea drugs may exert their peripheral actions in adipose tissue by using (part of) the insulin postreceptor signalling cascade at the step of activation of a GPI-specific phospholipase C.
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PMID:The sulphonylurea drug, glimepiride, stimulates release of glycosylphosphatidylinositol-anchored plasma-membrane proteins from 3T3 adipocytes. 767 37

Two membrane-photosensitizing dyes were used to investigate whether selected sites in the plasma membrane vary in their sensitivity to damage by singlet oxygen (1O2*) and, if so, what factors are responsible for the variation. The relative ability of Rose bengal (RB) and merocyanine 540 (MC540), both of which localize in the plasma membrane and produce 1O2*, to photosensitize five plasma membrane functions in P388D1 cells was evaluated. The five membrane functions assessed were: plasma membrane potential, proline transport, facilitated glucose diffusion, 5'-nucleotidase activity, and dye exclusion. Photosensitization efficiency by RB varied by a factor of 188 for these membrane functions, whereas for MC540 a range of only 24 was found. RB was a more efficient photosensitizer than MC540 but the relative efficiencies varied with the membrane function. The wide range of P50 values for RB suggests that it binds selectively to membrane sites where it causes damage with high efficiency; possibly a non-1O2* mechanism is involved. In contrast, MC540 photosensitized the three membrane functions involving integral membrane proteins about equally suggesting that differences are due to small variations in the distribution of MC540 in the plasma membrane and/or variations in the inherent reactivity of the membrane targets with 1O2*. The results indicate that the lability of membrane sites to photosensitization depends both on their inherent reactivity with 1O2* and the relative location of specific protein and dye molecules.
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PMID:Influence of dye and protein location on photosensitization of the plasma membrane. 784 Nov 81

Lung surfactant was isolated from human amniotic fluid collected at term and studied with reference to the material isolated from human and rabbit lung lavage. The isolated material showed 58 per cent lipid by dry weight, 29 per cent protein and relatively smaller amounts of nucleic acids, sialic acid and hexose. Phosphatidyl choline was the predominant phospholipid species and accounted for 46 per cent of the total lipid by weight, followed by phosphatidyl glycerol (7%) and phosphatidyl ethanolamine (5%). Cholesterol was the major neutral lipid fraction present (10%) and was almost entirely in the free form. Other lipid fractions present in minor quantity were triglycerides, esterified cholesterol, phosphatidyl serine, phosphatidyl inositol and sphingomyelin. The material contained a very high degree of alkaline phosphatase activity, while other enzymes such as acid phosphatase, glucose-6-phosphatase, ATPases, 5'-nucleotidase and beta-N-acetyl glucosaminidase were also present.
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PMID:Isolation & chemical composition of lung surfactant from human amniotic fluid. 800 43


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