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)

Hepatic function can be monitored using exogenous (e.g., sulfobromophthalein, indocyanine green, antipyrine, aminopyrine, galactose) and endogenous substances (e.g., bile acids, PT/PTT, albumin, ammonia, bilirubin). Test of hepatic necrosis include aspartate aminotransferase, and alanine aminotransferase. The hepatobiliary system can be assessed using alkaline phosphatase, 5'-nucleotidase, gamma-glutamyl transpeptidase, ultrasound, and iminodiacetic acid scans.
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PMID:Monitoring hepatic function. 306 53

Radiation-inactivation studies were performed on brush-border-membrane vesicles purified from rat kidney cortex. No alteration of the structural integrity of the vesicles was apparent in electron micrographs of irradiated and unirradiated vesicles. The size distributions of the vesicles were also similar for both populations. The molecular sizes of two-brush-border-membrane enzymes, alkaline phosphatase and 5'-nucleotidase, estimated by the radiation-inactivation technique, were 104800 +/- 3500 and 89,400 +/- 1800 Da respectively. Polyacrylamide-gel-electrophoresis patterns of membrane proteins remained unaltered by the radiation treatment, except in the region of higher-molecular-mass proteins, where destruction of the proteins was visible. The molecular size of two of these proteins was estimated from their mobilities in polyacrylamide gels and was similar to the target size, estimated from densitometric scanning of the gel. Intravesicular volume, estimated by the uptake of D-glucose at equilibrium, was unaffected by irradiation. Uptake of Na+, D-glucose and phosphate were measured in initial-rate conditions to avoid artifacts arising from a decrease in the driving force caused by a modification of membrane permeability. Na+-independent D-glucose and phosphate uptakes were totally unaffected in the dose range used (0-9 Mrad). The Na+-dependent uptake of D-glucose was studied in irradiated vesicles, and the molecular size of the transporter was found to be 288,000 Da. The size of the Na+-dependent phosphate carrier was also estimated, and a value of 234,000 Da was obtained.
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PMID:Radiation-inactivation studies on brush-border-membrane vesicles. General considerations, and application to the glucose and phosphate carriers. 342 23

A method using low concentrations of formaldehyde and dithiothreitol was applied to obtain 'right-side out' luminal plasmalemma-derived vesicles from bovine aortic endothelial cells (EC) in culture, and from human umbilical vein and bovine or porcine aortas perfused ex vivo with the vesiculation solution. Vesicle formation and shedding were examined by phase-contrast microscopy and by transmission (TEM) and scanning electron microscopy (SEM). Vesicles showed the characteristic trilaminar pattern of the unit membrane and did not contain cellular organelles. As detected in freeze-fracture preparations, vesicle membrane displayed intramembrane particles and filipin-detectable cholesterol. Like EC plasmalemma, vesicle surface was heavily stained by Ruthenium Red and bound under a normal pattern cationized ferritin and ferritin hydrazide. As indicated by lectin agglutination assays and by ultrastructural cytochemistry, vesicles maintained on their ectodomains glycoconjugates bearing monosaccharides such as N-acetyl-neuraminic acid, beta-N-acetylglucosamine and beta-D-galactose, and expressed 5'-nucleotidase activity. The electrophoretic profiles of externally disposed 125I-labelled polypeptides of vesicles were found to be similar to those of intact EC. Chemically-induced vesiculation appears as a suitable method to obtain EC plasmalemma for studying its composition and functions in various vascular beds.
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PMID:Endothelial cell plasma membrane obtained by chemically induced vesiculation. 359 39

Uterine plasma membrane preparations were obtained by centrifugation on discontinuous sucrose gradients. The specific activity of the plasma membrane marker 5'-nucleotidase was increased 10-fold while the specific activity of glucose-6-phosphatase was increased 3-fold. Electron microscopy showed mainly closed vesicles having diameters mainly in the range of 0.1 to 0.4 micron and an absence of other recognizable organelles such as mitochondria. D-Glucose transport was inhibited by sulfhydryl reagents, phloretin, and cytochalasin B. Uptake was prevented at high osmotic pressures. The Km of glucose transport was 12.2 +/- 1.1 mM. Studies of the inhibition of [3H]cytochalasin B binding by D-glucose indicated that the value of the Kd of the cytochalasin B-transporter complex was larger than 1 microM. These data demonstrate the potential usefulness of these preparations in the study of glucose transport in rat uterus and its control by steroid hormones.
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PMID:Glucose transport by uterine plasma membranes. 403 86

Renal brush-border membrane vesicles were irradiated in the frozen state with a high energy electron beam. The integral membrane proteins, alkaline phosphatase and 5'-nucleotidase, each showed a single exponential loss of activity with radiation dose, indicating target sizes of 67,000 and 58,000 daltons, respectively. Inactivation of sodium-dependent phlorizin binding to the brush-border membrane D-glucose transporter was more complex. One-half of the phlorizin binding sites were lost after even the smallest doses of radiation suggestive of large functional units (greater than 4 X 10(6) daltons) for a subpopulation of phlorizin binding proteins. The remaining sites behaved as a single radiation target of 110,000 +/- 8,000 daltons and retained the kinetic characteristics commonly associated with phlorizin binding to the glucose transporter. Thus, the data are consistent with the assignment of a molecular weight of 110,000 to the phlorizin binding moiety of the brush-border membrane D-glucose transport protein.
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PMID:Radiation inactivation studies of the renal brush-border membrane phlorizin-binding protein. 628 75

The ability of nonionic detergents to solubilize the membrane-bound enzymes of the brush-border plasma membrane of Hymenolepis diminuta was investigated. Of the detergents tested (Triton X-100, Tween 80, Brij 35, Lubrol PX and WX, W-1, and beta-octyl-D-glucoside), only Triton was an effective solubilizing agent. Optimal solubilization was achieved by incubating an isolated fraction of the brush-border membrane in the presence of 1% Triton X-100 for 60 min at 37 C, followed by centrifugation at 100,000 g for 60 min at 25 C. This treatment resulted in solubilization of 94% of the alkaline phosphohydrolase, 91% of the phosphodiesterase and ribonuclease, and 88% of the 5'-nucleotidase activities. The pH optima for enzymes solubilized in nonionic and ionic detergents (Triton and sodium dodecyl sulfate, respectively) did not differ. Isoelectric focusing of the Triton-solubilized material demonstrated the presence of at least 14 polypeptides, a majority of which had isoelectric points below pH 7.
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PMID:Solubilization of the membrane-bound enzymes of the brush-border plasma membrane of Hymenolepis diminuta (Cestoda) using nonionic detergents. 628 6

To characterize the placental amino acid transport systems, L-alanine and L-leucine uptakes were studied using microvillous brush border membrane vesicles prepared from human placenta. The specific activities of alkaline phosphatase and 5'-nucleotidase in the membrane preparation were enriched 9-11 times as high as those in the homogenate. Intravesicular water (IVW) volume determined with 3-O-methyl-D-glucose was 0.59 microliters/mg protein. The saturation kinetics of L-leucine uptake by the vesicles equilibrated with Na+ gave a single set of Km (4.2mM) and Vmax (1.16 mumol/ml IVW/30s). These parameters were clearly different from those for L-alanine uptake reported previously (Asai et al.: Biochem. Int., 4:377, 1982). In the presence of an inward Na+-gradient L-leucine uptake was stimulated about 2 times, but transient accumulation was not observed differing from L-alanine uptake. Discrimination of the neutral amino acid transport systems in the presence of an inward 100mM Na+-gradient revealed that the relative contributions of A, ASC and L systems, and simple diffusion were 55, 20, 15 and 10% for L-alanine, and 45, 0, 15 and 40% for L-leucine, respectively. The results indicate that the neutral amino acid transport systems in the human placental microvillous membranes are clearly different between L-alanine and L-leucine.
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PMID:[Studies on the amino acid transport systems in the human placenta--L-alanine and L-leucine uptake by microvillous brush border membrane vesicles]. 629 24

A marked increase in the activities of rat liver plasma-membrane (Na+ + K+)-stimulated ATPase and microsomal Ca2+-stimulated ATPase was observed 18h after partial hepatectomy. Lipid analyses for both membrane preparations reveal that in partially hepatectomized rats the cholesterol and sphingomyelin content are decreased with a subsequent decrease in the cholesterol/phospholipid molar ratio compared with those of sham-operated animals. Changes in the allosteric properties of plasma-membrane (Na+ + K+)-stimulated ATPase by F- (as reflected by changes in the Hill coefficient) indicated a fluidization of the lipid bilayer of both membrane preparations in 18 h-regenerating liver. The amphipathic dodecyl glucoside incorporated into the hepatic plasma membranes evoked a marked increase in the (Na+ + K+)-stimulated ATPase and 5'-nucleotidase activities. The lack of effect of the glucoside on the Lubrol-PX-solubilized 5'-nucleotidase indicates that changes in the activities of the membrane-bound enzymes caused by the glucoside are due to modulation of the membrane fluidity. Dodecyl glucoside appears to increase the membrane fluidity, evaluated through changes in the Hill coefficient for plasma-membrane (Na+ + K+)-stimulated ATPase. The biological significance of these data is discussed in terms of the differences and changes in the interaction of membrane-bound enzymes with membrane lipids during liver regeneration.
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PMID:Alterations in the activities of hepatic plasma-membrane and microsomal enzymes during liver regeneration. 630 44

We have examined the interactions of the membrane-bound enzymes, 5'-nucleotidase and acetylcholinesterase from bovine tissues with lectins and shown that glycosylation contributes significantly to the polymorphism of these enzymes, in a tissue-specific manner. Lectins which bind 5'-nucleotidase also inhibit its catalytic activity to various degrees. We found different specificities with 5'-nucleotidases from various cell types: for example lymphocyte 5'-nucleotidase did not interact with wheat germ agglutinin, in contrast with 5'-nucleotidases from hepatocyte and caudate nucleus membranes. Treatment with glycohydrolases, alpha-D-mannosidase and neuraminidase, suggested that the latter enzymes possess sialic residues which are absent in the lymphocyte enzyme. Interactions of acetylcholinesterase with lectins were demonstrated by sedimentation analysis and binding to immobilized lectins, but its activity was generally not affected. A notable exception was lymphocyte acetylcholinesterase which was inhibited by the fucose-binding Ulex europeus agglutinin. This inhibition was relieved by alpha-L-fucose but not by alpha-D-fucose and reduced after treatment with alpha-L-fucosidase. In addition this enzyme differs from acetylcholinesterases from other tissues by its higher Km value, although it appears immunologically equivalent. The different forms of acetylcholinesterase from the same tissue may differ in their interactions with lectins. In muscle for example G4 carries carbohydrate chains of the complex type whereas G1 appears to possess only the high mannose type. We discuss the possible relationships between these forms.
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PMID:Interactions with lectins indicate differences in the carbohydrate composition of the membrane-bound enzymes acetylcholinesterase and 5'-nucleotidase in different cell types. 632 88

A major role of the Golgi apparatus in liver is the terminal glycosylation of secreted serum proteins and of plasma membrane glycoproteins. Galactosyltransferase is a membrane-bound Golgi enzyme that transfers galactose directly from uridine diphosphogalactose (UDP-Gal) to terminal N-acetylglucosamine groups of N-asparagine-linked glycoproteins during secretion. Sialytransferase then transfers sialic acid from cytidine monophosphosialic acid (CMP-NAN) to the newly added terminal galactose of the glycoprotein. In the cell, the transfer reaction must occur on the lumen side of the Golgi membrane. UDP-Gal is synthesized mainly in the cytoplasm and CMP-NAN is synthesized in the nucleus in liver. An important question for understanding the mechanism is, how do these nucleotide sugars gain access to the transferases? A second question involves uridine diphosphate (UDP), a highly inhibitory product of galactosyltransferase. How is UDP removed from the lumen of the Golgi fast enough to prevent product inhibition of the galactosyltransferase? We have shown that isolated Golgi, although vesiculated, retains its original orientation. The vesicles are oriented with greater than 90% of both galactosyltransferase and sialyl-transferase on the luminal side of the vesicles. Using intact vesicles, we can show that UDP-Gal is taken up via a saturable carrier system present in the Golgi membrane. During galactosylation in vitro, UDP formed in the lumen of Golgi vesicles is rapidly converted to UMP by a nucleoside diphosphatase in the lumen. Uridine monophosphate, which is much less inhibitory to the galactosyltransferase than UDP, is then transported out of the lumen by a second carrier and is broken down further to uridine by 5'-nucleotidase on the cytoplasmic side of the Golgi vesicles. The transport of nucleotides appears unique to the Golgi membranes, since neither rough endoplasmic reticulum nor plasma membrane vesicles from rat liver accumulate these nucleotides.
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PMID:Mechanism of glycosylation in the Golgi apparatus. 634 57


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