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)

Plasma membrane vesicles were isolated from a subline of L929 mouse fibroblasts grown on defined medium in the absence of serum. These vesicles were not significantly contaminated by mitochondria or endoplasmic reticulum. The isolation procedure, a modification of that originally developed by McKeel and Jarett (McKeel, D.W., and Jarett, L. (1970) J. Cell Biol. 44, 417-432) employs mechanical homogenization in isotonic medium followed by differential centrifugation. The resultant plasma membrane vesicles take up radioactivity when exposed to uniformly labeled nucleosides. Two subfractions of the plasma membrane were isolated, distinguished by their differing activity of 5'-nucleotidase and (Na+,K+)-stimulated ATPase, two well known plasma membrane enzyme markers. Uptake of nucleoside radioactivity was extensively studied in one subfraction; it was linear with time and membrane concentration over ranges used for the studies. Apparent Km values for uptake of radioactivity from adenosine, inosine, and uridine were 7.1 +/- 26 muM, respectively. Uptake of radioactivity from all three nucleosides exhibits a broad pH optimum from pH 7 to pH 9, but falls off rapidly at lower pH. N-Ethylmaleimide was an effective inhibitor of uptake of radioactivity from all three nucleosides; uptake of radioactivity from uridine is more sensitive than uptake of radioactivity from the purine nucleosides. Adenosine inhibited uptake of radioactivity from inosine more than from uridine. Inosine inhibited the uptake of radioactivity from adenosine, but uridine did not. Caffeine and 6-methylaminopurine riboside (6-N-methyladenosine differentially inhibit uptake of radioactivity from adenosine and inosine, and thus the vesicles apparently possess seperate transport systems for uptake of radioactivity from purine nucleosides and from uridine.
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PMID:Transport mechanisms in isolated plasma membranes. Nucleoside processing by membrane vesicles from mouse fibroblast cells grown in defined medium. 0 4

1. Adenylate cyclase (EC 4.6.1.1) activity was characterized in human liver, and its subcellular distribution compared with that of three other potential enzyme markers of the pericellular membrane: leucine aminopeptidase (EC 3.4.11.1), gamma-glutamyltransferase (EC 2.3.2.2) and 5'-nucleotidase (EC 3.1.3.5). Although these three enzyme activities were detected in each of the subcellular fractions studied, 85% of the total adenylate cyclase activity was found in the 1000 g pellet ('nuclear' fraction) with a threefold increase in specific activity as compared with the homogenate. No adenylate cyclase activity existed in the 150 000 g supernatant fraction. 2. In the 'nuclear' fraction, adenylate cyclase activity was increased in a dose-dependent fashion by glucagon with a half-maximal stimulation at 10 nmol/l and a maximal four- to seven-fold increase at 1 mumol/l. Catecholamines activated adenylate cyclase 2.5- to three-fold, with an order of potency (protokylol greater than isoprenaline greater than adrenaline greater than noradrenaline) typical of a beta 2-adrenoreceptor. Prostaglandin E1 and NaF also stimulated cyclase two- and four-fold respectively. Insulin, serotonin, dopamine, thyroid-stimulating hormone and ACTH had no effect. Adenosine provoked a weak inhibition at 0.1 mmol/l. Finally guanosine triphosphate and 5'-guanylyl imidodiphosphate induced a marked increase in basal activity, four- and eight-fold respectively, but both reduced the relative increase in enzyme activity due to glucagon or adrenaline. 3. Cyclase from foetal liver (12--16 weeks old) and cirrhotic adult liver appeared to behave similarly to that from normal liver; however, foetal cyclase was more active, and cirrhotic enzyme less active than normal adult liver. Both systems responded to catecholamines via a beta 2-adrenoreceptor. 4. These results validate the use of rat liver adenylate cyclase as a tool for pharmacological and physiological studies.
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PMID:The adenylate cyclase system in human liver: characterization, subcellular distribution and hormonal sensitivity in normal or cirrhotic adult, and in foetal liver. 4 65

The histochemical distribution of 14 enzymes in the human amnion at term are described. Adenosine triphosphatase, 5'-nucleotidase, acid phosphatase and nonspecific esterase show continuous gradations of enzyme activity. Cells with intense activity are prominent in acid phosphatase and nonspecific esterase preparations. A distinct subpopulation of amniotic cells can be defined by their alkaline phosphatase activity. The possible correlations with morphological studies are discussed.
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PMID:Enzyme histochemical patterns in the normal human amnion: amniotic histochemical patterns. 4 99

Three parts were distinguished by electron microscopy and by enzyme histochemistry at the boundary zone between the white and red pulp of the human spleen. The first was the inner layer of the perifollicular region, composed of medium-sized lymphocytes with abundant free ribosomes in their cytoplasm. A small number of reticulum cells intervened among these lymphocytes. This inner layer was considered to correspond to the "Follikelaussenzone" (Strasser). The second was the outer layer of the perifollicular region, composed of a meshwork of reticulum cells with reticular fibers, and sheathed and non-sheathed arteries. Small and medium-sized lymphocytes, granulocytes, erythrocytes, platelets, and a small number of plasma cells were observed in the mesh spaces. This outer layer was considered to correspond to the "marginal zone" (Snook). At the outermost part of this layer, the venous sinus appeared. There was no distinct border between this layer and the red pulp. The third was the neighboring region of the periarterial lymphoid sheath, showeing similar structure and cellular components to the outer layer of the perifollicular region. It was characteristic feature for the lymphocytes and some of the reticulum cells of this region to have a strong activity for alkaline phosphatase reaction, while the lymphocytes of the outer layer showed only a weak activity. Adenosine triphosphatase and 5'-nucleotidase activities were demonstrated on the lymphocytes of these three parts of the boundary zone as well as the lymph follicle. Different activities for these enzyme reactions may indicate the functional properties of the B-cell system.
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PMID:An electron microscopic and enzyme histochemical study of the boundary zone between the white and red pulp of the human spleen. 14 41

The present study deals with the distribution of adenosine triphosphatase and 5'-nucleotidase in the various constituents of thoracic ganglia and associated nerve of Periplaneta americana. The localization of both the enzymes in the thoracic ganglia is identical. The neural lamella is devoid of any activity for both the enzymes. The ganglion cells are intensely positive at their borders. The neuronal cell surface and/or glial cell processes which envelope the neurons show intense activity for these enzymes. Adenosine triphosphatase and 5'-nucleotidase are present around "giant fibres" and small axons. The activity appears to confine itself in the sheaths. The cytoplasm and the nuclei of the neurons are devoid of enzymatic activity, whereas the nucleoli are slightly active. The nerves are positive for both the enzymes. The role of these enzymes at different sites has also been discussed.
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PMID:Histochemical studies on the distribution of adenosine triphosphatase and 5'-nucleotidase amongst the constituents of the thoracic ganglia and the associated nerve of Periplaneta americana. 14 3

Membrane function was examined in cultured cells from cystic fibrosis patients by assaying several enzymes on intact skin fibroblasts attached to culture dishes. This technique required few cells and minimized disruption of cellular organization. Comparison of enzyme activities of intact and broken cells showed that 12% of total glucose-6-phosphate dehydrogenase, a cytoplasmic enzyme, was measurable using intact cells, while all adenosine monophosphatase was measurable using intact cells. Alkaline paranitrophenylphosphatase activity was divided between the cell surface and interior. Substrate competition experiments indicated that substrate specificities for adenosine monophosphatase and paranitrophenylphosphatase activities were different. Adenosine monophosphatase activities of 2 control and 2 cystic fibrosis strains fluctuated similarly during the cell culture cycle. The apparent Km values relative to adenosine monophosphate were similar in all strains. A chromatographic fraction of serum from a cystic fibrosis patient that was inhibitory to oyster ciliary activity had no effect on adenosine monophosphatase activity of normal fibroblasts. Furthermore, fractions of media from cystic fibrosis homozygote and heterozygote fibroblast cultures were not inhibitory to adenosine monophosphatase activities of intact normal fibroblasts or of part iculate fractions prepared from them. In light of previous studies that showed that factors from cystic fibrosis serum of culture medium disrupted specific membrane activities, it is proposed that the cystic fibrosis factor interacts with the plasma membrane, interfering most conspicuously with the protein functions that are sensitive to changes in their membrane environment.
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PMID:Surface enzymes in cultured fibroblasts from cystic fibrosis patients. 18 10

Radioactively labelled adenosine and adenine were rapidly taken up by isolated rat fat cells, and incorporated into nucleotides, of which ATP dominated. The overall process had an apparent Km of 1--5 micrometers. During incubation, especially in the presence of lipolytic agents, there was a reduction in labelled ATP with a compensatory increase in ADP, AMP, cAMP and nucleosides. The build-up of adenosine during incubation was inhibited by theophylline, which inhibits 5'-nucleotidase. Radioactivity released from perifused fat cells consisted mainly of nucleoside material, of which adenosine predominated. Lipolytic stimulation caused no significant increase in nucleoside outflow from perifused cells, whereas oxygenation was capable of reducing this outflow. It is concluded that adenosine is formed by fat cells as a consequence of ATP breakdown. Stimulation of lipolysis during activation of the sympathetic nerves leads to reversible ATP breakdown and adenosine release. Adenosine might therefore act as a modulator of lipolysis in vivo under these conditions, even though it does not serve as a feed back regulator in the proper sense.
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PMID:Uptake and release of adenosine in isolated rat fat cells. 22 Aug 45

Suspensions of endocrine pancreas cells were prepared by shaking collagenase-isolated rat islets of Langerhans in calcium-free buffer. When incubated with 1.0 mM substrate at pH 7.4, the cells split Pi from 5'-AMP at a rate of 87 nmol/h per microgram DNA, and from beta-glycerophosphate at a rate of 25 nmol/h per microgram DNA. Km for 5'-AMP was about 54 microM. Adenosine or theophylline inhibited the 5'-AMP hydrolysis. Homogenization of the cells increased the activity toward 5'-AMP by 23% and that toward beta-glycerophosphate by 115%. Injecting rats with cortisone had no effect on the 5'-AMP hydrolysis by whole cells but significantly increased the activity in cell homogenates; the intracellular activity toward 5'-AMP was more than doubled by the cortisone treatment. Staining whole islet cells for 5'-AMP-splitting activity resulted in a demarcation of the cell periphery in control rats. Cells from cortisone-treated rats showed heavier deposits of reaction product, and their cell periphery did not stand out as clearly. It is suggested that 5'-nucleotidase is largely an ectoenzyme in normal rat islet cells. The cells also contain an as yet unidentified intracellular phosphatase that seems to be solely responsible for the increased hydrolysis of 5'-AMP in cortisone-treated rats.
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PMID:5'-AMP hydrolysis by suspensions and homogenates of pancreatic islet cells from normal and cortisone-treated rats. 38 76

The regulation by ATP of Cl- secretion in T84 cells grown on filters was investigated by measuring short-circuit current (Isc = net Cl- secretion). ATP (greater than or equal to 10 microM) added to the basolateral side markedly stimulated Isc both in the presence and absence of forskolin-activated Isc. Fluorescence microscopy of cells loaded with the Ca2+ indicator fura-2 showed that ATP stimulated a transient increase in intracellular free Ca2+ concentration [Ca2+]i. The augmentation of forskolin-stimulated Isc by ATP was at least partly caused by mobilization of Ca2+ from an internal store because prior depletion of the store using ionomycin prevented the response. The activity sequence for stimulation of Isc in the presence of forskolin was adenosine 5'-O-(3-thiotriphosphate) = 5'-adenylylimidodiphosphate (AMP-PNP) greater than ATP greater than ADP greater than AMP, suggesting the presence of a P2 purinergic receptor. Neither beta, gamma-methyleneadenosine 5'-triphosphate nor alpha, beta-methyleneadenosine 5'-triphosphate increased the Isc. Stimulation of Isc by ATP in the absence of forskolin was at least partly due to the breakdown of ATP to AMP and adenosine, which act at P1 receptors to stimulate Isc, since 1) inhibition of the ecto-phosphohydrolase 5'-nucleotidase by alpha, beta-methylene-ADP partially inhibited stimulation of Isc by ATP, 2) the adenosine receptor antagonists caffeine and 8-phenyltheophylline markedly inhibited the ATP-stimulated Isc, and 3) AMP-PNP, a weakly hydrolyzable analogue of ATP, caused a much smaller increase in Isc compared with ATP. Adenosine had no effect on [Ca2+]i.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Purinergic receptor activation of Cl- secretion in T84 cells. 131 Feb 17

Prevention of nucleoside loss in bile is physiologically desirable because hepatocytes are the main source of nucleosides for animal cells which lack de novo nucleoside biosynthesis. We have demonstrated a Na+ gradient-energized, concentrative nucleoside transport system in canalicular membrane vesicles (CMV) from rat liver by studying [3H]adenosine uptake using a rapid filtration technique. The Na(+)-dependent nucleoside transporter accepts purine, analogues of purine nucleosides and uridine; exhibits high affinity for adenosine (apparent Km, 14 microM); is not inhibited by nitrobenzylthioinosine or dipyridamole, and is present in CMV but not in rat liver sinusoidal membrane vesicles. Adenosine transport in right side-out CMV was substantially greater than with inside-out CMV. CMV also contain abundant ecto-ATPase and ecto-AMPase (5'-nucleotidase). These ectoenzymes were shown to degrade nucleotides into nucleosides which were conserved by the Na(+)-dependent nucleoside transport system.
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PMID:A nucleoside transporter is functionally linked to ectonucleotidases in rat liver canalicular membrane. 131 67


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