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At least 883 records · Page 49Linked to original sources
PubMed1985

5-Nucleotidase activity in isolated follicular dendritic cells.

Follicular dendritic cells isolated from mouse lymph nodes were incubated in the presence of AMP to test 5-nucleotidase (5-Nase) activity. Ultrastructural observations showed the presence of 5-Nase on external membranes but also some activity inside the nucleus. 5-Nase was found associated to Fc receptors labelled with homologous immunoglobulins fixed on colloidal gold particles. Lymphocytes and macrophages, found in association with the follicular dendritic cells, were either 5-Nase positive or negative. The hypothetical roles played by 5-Nase in germinal centers are discussed.

5'-Nucleotidase↗
PubMed1989

Pyrimidine nucleotides impair phosphoribosylpyrophosphate (PRPP) synthetase subunit aggregation by sequestering magnesium. A mechanism for the decreased PRPP synthetase activity in hereditary erythrocyte pyrimidine 5'-nucleotidase deficiency.

The activity of phosphoribosylpyrophosphate (PRPP) synthetase (ATP: D-ribose-5-phosphate pyrophosphotransferase, EC 2.7.6.1) is decreased in the erythrocyte in hereditary pyrimidine 5'-nucleotidase (P5N) deficiency. Given the increased pyrimidine nucleotide content of the P5N-deficient erythrocyte, we evaluated the effects of prototypic pyrimidine nucleotides on the activity of PRPP synthetase. In normal hemolysate a 1.0 mM combination of cytidine tri-, di- and monophosphate (CTP/CDP/CMP) inhibited PRPP synthetase activity and changed the ribose 5-phosphate (R5P) saturation curve from a hyperbola to a biphasic shape. Untreated crude hemolysate from P5N-deficient erythrocytes showed a biphasic R5P kinetic curve. Since the activity of PRPP synthetase is dependent on its state of subunit aggregation, we examined PRPP synthetase subunit aggregation using gel permeation chromatography. P5N-deficient erythrocytes had a decreased absolute amount of aggregated PRPP synthetase and almost a total loss of disaggregated PRPP synthetase. Using normal hemolysate, 1 mM CTP/CDP/CMP interfered with the ability of 1.0 mM ATP and 2.0 mM MgCl2 to promote PRPP synthetase subunit aggregation. Increasing the MgCl2 to 6.0 mM overcame the inhibitory effect of CTP/CDP/CMP. Thus, the decreased PRPP synthetase activity of the P5N-deficient erythrocyte is due, at least in part, to the ability of the accumulated pyrimidine nucleotides to sequester magnesium and to interfere with the subunit aggregation of PRPP synthetase.

5'-Nucleotidase↗
PubMed1984

Effect of dimethylsulfoxide and butyrate on 5'-nucleotidase of human renal carcinoma cells.

The effect of dimethylsulfoxide (DMSO) and butyrate, agents which induce differentiation of certain cancer cells, on membrane associated 5'-nucleotidase (5'-NT) of 2 human renal carcinoma cell lines (Cur and Caki) was investigated. Under a variety of conditions of agent addition, 5'-NT specific activity increased in Cur and decreased in Caki cells. This opposite response pattern was observed for assays performed on lysates at pH 9.0 and 7.4 and assays with intact cell monolayers, even under conditions of identical cellular growth inhibition. It is concluded that the cell lines responded in a fundamentally different way to the chemical agents. An increase in 5'-NT has correlated with cell maturation for a number of processes. The DMSO induced increase in Cur 5'-NT was dependent on protein synthesis.

5'-Nucleotidase↗
PubMed1984

A specific harmaline-evoked increase in cerebellar 5'-nucleotidase activity.

This study examines harmaline-induced changes in 5'-nucleotidase (5'-ND) activity in cerebellar fractions from rats with an intact inferior olive (IO) or prior destruction of the IO by 3-acetylpyridine (3-AP) intoxication. Harmaline markedly increased 5'-ND activity in the crude homogenate (P less than 0.05) and P2 fraction (P less than 0.001) of cerebella from rats with an intact IO. This increase was absent in the P1, P3 and S3 fractions and it was abolished by 3-AP olivectomy. It was also absent in basal ganglia P2 fractions. Since harmaline produces rhythmic complex spike discharges of Purkinje cells by activating IO neurons [4, 18], these data suggest that climbing fiber activation per se increases 5'-ND activity in the P2 fraction. This raises the possibility that a climbing fiber-induced local increase in 5'-ND activity at parallel fiber-Purkinje cell synapses results in a local increase in adenosine concentration. This may account for climbing fiber-evoked suppression of simple spike activity [12, 13, 28].

5'-Nucleotidase↗
PubMed1982

Studies on some molecular properties of cytosol 5'-nucleotidase from rat liver.

A cytosol 5'-nucleotidase was purified from rat liver. It appeared to be homogeneous on the criteria of polyacrylamide gel electrophoresis. We estimated the approximate molecular weight of the enzyme to be 200 000 and concluded that the enzyme most likely exists in the native state as a tetramer. Our results suggest that adenine nucleotides, which are activators of the enzyme, induce its conformational change.

5'-Nucleotidase↗
PubMed1983

ACYL group composition of lipids and the activities of (Na+ + K+)-ATPase, 5'-nucleotidase and gamma-glutamyltranspeptidase in salivary glands and kidneys of rats fed diets containing different dietary fats.

Two nutritional models, an essential fatty acid deficiency model and the feeding of saturated versus unsaturated fats, were used in a feeding study in order to assess the relationship between tissue fatty acid composition and the activities of some membrane-associated enzymes. Purified diets containing 7% hydrogenated coconut oil, 7% corn oil, 10% safflower oil or butter were fed to rats for a total of 49 weeks (1 week of pregnancy, 3 weeks of lactation and 45 weeks post-weaning). Tissue homogenates from submandibular salivary glands and kidneys were analyzed for fatty acid composition of total lipids and phospholipids. Changes in fatty acid patterns typical of essential fatty acid deficiency such as an increase in the levels of 16:1 and 18:1, a decrease in 18:2 and 20:4 and an accumulation of 20:3 omega 9 were observed in salivary glands and kidneys of rats fed the deficient diet. Tissues of rats fed 10% butter also showed fatty acid compositional changes which were somewhat similar to those in essential fatty acid deficiency, but to a lesser degree. The activities of ouabain-sensitive (Na+ + K+)-ATPase were higher in homogenates of salivary glands and kidneys of the deficient rats and those fed butter as compared with their controls. The results suggest a relationship between the double bond index of fatty acids as an indication of membrane lipid fluidity and allosteric modification of (Na+ + K+)-ATPase activity. However, other explanations for the observed changes in (Na+ + K+)-ATPase activity cannot be ruled out. There were no diet-related differences in the activities of gamma-glutamyltranspeptidase or 5'-nucleotidase.

5'-Nucleotidase↗
PubMed1987

Cytosol 5'-nucleotidase from Artemia embryos. Purification and properties.

Cytosol 5'-nucleotidase (EC 3.1.3.5) has been purified near homogeneity from Artemia embryos. The enzyme cleaves preferentially IMP and GMP, and to a lesser extent other 5'-mononucleotides. The substrate-velocity plot was hyperbolic with GMP and sigmoidal with AMP. The hydrolysis of GMP is stimulated both by ATP and beta, gamma-methyleneadenosine 5'-triphosphate with the same activation constant of around 0.6 mM. Both nucleotides decreased S0.5 without affecting V. The molecular mass of the native purified enzyme was 165 kDa, and one major band of 42 kDa was detected after sodium dodecyl sulphate polyacrylamide gel electrophoresis.

5'-Nucleotidase↗
PubMed1984

In vitro effects of lead, mercury and cadmium on the enzymic activity of red-blood cell pyrimidine 5'-nucleotidase.

The decrease of pyrimidine 5'-nucleotidase (P5N) in human erythrocytes, detected in persons occupationally exposed to lead (Pb), is not an in vitro artefact resulting from the release of lead during erythrocyte hemolysis but is a true reflection of the enzyme activity in vivo. Like Pb, mercury (Hg) and cadmium (Cd) ions exhibit an important in vitro inhibitory action on the P5N enzymic activity. However, when the metals are preincubated as metallothionein complexes with P5N preparations, their inhibitory power disappears.

5'-Nucleotidase↗
PubMed1988

Comparison of inhibition of erythrocyte pyrimidine 5'-nucleotidase and delta-aminolevulinic acid dehydratase by lead.

The effect of lead on the activities of erythrocyte pyrimidine 5'-nucleotidase (P5N) and delta-aminolevulinic acid dehydratase (ALAD) was investigated in control and lead-exposed workers. The inhibitory effect of lead in vivo and in vitro was more remarkable on the ALAD than on the P5N activity values. It was demonstrated that the pH optimum of both ALAD and P5N in lead workers shifts to the acidic side (nearly pH 6.0) compared to that in control workers.

5'-Nucleotidase↗
PubMed1985

Changes in 5'-nucleotidase and adenosine deaminase distribution across the rat left ventricle wall during growth and aging.

The concentrations of the adenosine-generating enzyme 5'-nucleotidase (5'-N) and of the adenosine-degrading enzyme adenosine deaminase (ADA) in the rat left ventricle change as a function of the age of the animal. The enzyme distribution across the left ventricle wall is non-uniform in adult or old rats (in the case of 5'-N) or in all age-groups (in the case of ADA). In the oldest rats, 5'-N activity exhibited a significant increase in the mid-myocardium and in the inner myocardial layers as compared with the young adult controls.

5'-Nucleotidase↗
PubMed1987

Cytochemical localization of Mn2+-dependent pyrimidine 5'-nucleotidase activity in isolated rod outer segments.

A cytochemical method was developed for localization in isolated rod outer segments of manganese-dependent pyrimidine 5'-nucleotidase (MDPNase), an enzyme activity with possible relevance to shedding that we recently reported in photoreceptors and retinal pigment epithelial (RPE) cells in the intact rat retina. The purpose of this study was to eliminate the possibility that the previously observed cytochemical staining of the rods was due to diffusion of reaction product from the RPE cell lysosomes, which were also heavily stained. Rod outer segments (ROS) were isolated on continuous sucrose gradients from retinal homogenates prepared from rats raised in cyclic light (12 hr light:12 hr dark) and killed during the first 2 hr after light onset. ROS-containing bands were removed from the gradients and the isolated rods were fixed in 0.25% glutaraldehyde and pelleted. Chopped sections of the pellets were incubated in cytochemical medium for MDPNase activity and processed for light- and electron-microscopic localization of the enzyme activity. Two patterns of cytochemical staining were seen in ROS isolated from retinas obtained at this time of day. A few of the pellets contained clusters of ROS that were heavily coated along their surfaces and seemingly interconnected by thick strands of highly reactive extracellular material that displayed a punctate pattern of cytochemical staining. This material may have originated from the apical processes of the RPE cells, which were heavily stained in tissue fixed in situ around the time of light onset. The second staining pattern, visible only by electron microscopy, was more commonly observed. In the majority of the isolated ROS profiles, discrete streaks of cytochemical reaction product were seen in association with the internal aspects of the discs, at sites that seemed to correspond to the rims, and to narrow zones within the disc interiors. This distribution of reactive sites closely resembled that observed over most of the length of the ROS in the intact retina fixed at the same time of day. Occasionally, ROS profiles were encountered in which additional reactive sites were localized to the interdisc spaces between the plasma membrane and the rims of the discs. The latter pattern resembled the distribution of reaction product seen during this period over the tips of the ROS fixed in situ. As in the intact retinas, the cytochemical staining of the isolated ROS was inhibited by fluoride ions and strongly stimulated by manganese ions.(ABSTRACT TRUNCATED AT 400 WORDS)

5'-Nucleotidase↗
PubMed1982

Determination of 5'-nucleotidase activity in human erythrocytes and plasma using high-performance liquid chromatography.

A method is described for the determination of 5'-nucleotidase activity in human erythrocytes and plasma. Using reversed-phase high-performance liquid chromatography; the product (uridine) was separated from the substrate (uridine-5'-monophosphate) in less than 4 min. The activity determined closely agreed with that determined by the conventional method, in which the inorganic phosphate released is measured. The present method eliminates the need for dialysis of enzyme solution prior to the assay, and offers several advantages over other assay methods, including high sensitivity.

5'-Nucleotidase↗
PubMed1985

Localization of nucleoside phosphatases (ATPase and 5'-nucleotidase) and nuclear ribonucleoproteins in the human endometric glandular cells during the secretory phase.

Endometrial curettings from 3 healthy women between 16th and 19th d of the menstrual cycle were investigated employing ultracytochemical methods. In endometrial glandular cells ATPase and 5'-nucleotidase activities were demonstrated in the nuclei, nucleoli, and nuclear channel system (NCS), i.e., mainly in structures characterized ++as ribonucleoproteins according to the Bernhard method. The functional relationship between the NCS and the molecular biology of the endometrial glandular cell is discussed.

5'-Nucleotidase↗
PubMed1986

Evolution of localization of the reactions of adenosine triphosphatase (Mg++-ATP-ase), 5'nucleotidase (5'nt), alkaline phosphatase (AP), and acid phosphatase (AcP) in developing rat testis. I. Physiological conditions.

The experiments were performed upon the rats aged 1, 4, 7, 15, 30, 45, 60, 90 d, and 1,5 a. The behavior of the following reactions was described: for adenosine triphosphatase stimulated by Mg++(Mg++-ATP-ase), for 5'nucleotidase (5'Nt), for alkaline phosphatase (AP), for acid phosphatase (AcP). The first 3 are markers of the transport enzymes in cells, and the 4th is a marker of lytic processes. It was estimated on the basis of the examined reactions that a full metabolic maturity of the gonad was revealed since the 45th d of post-fetal life.

5'-Nucleotidase↗
PubMed1987

5'-Nucleotidase activity in cultured rat leptomeninges.

By means of a cytochemical procedure, 5'-nucleotidase activity was demonstrated in rat leptomeninges explanted to in vitro conditions. In organotypic type of culture, the enzyme activity was present on the membranes of cell bodies and their processes. High enzymatic activity was due to the cell-to-cell contact and also to pinocytosis and enhanced metabolism of nucleotides in meningeal cells in vitro.

5'-Nucleotidase↗
PubMed1987

Evolution of localization of reactions of adenosine triphosphatase (Mg++-ATP-ase), 5'nucleotidase (5'nt), alkaline phosphatase (AP), and acid phosphatase (AcP) in developing rat testis. II. After CdCl2 treatment.

The described experiments show the influence of a single dose of cadmium chloride (1.5 mg CdCl2/kg body weight applied intraperitoneally) on development of the male gonads from the 1st d of post-fetal life to 1.5 a of life. In the case of the enzymes triggering transportation processes, adenosine triphosphatase stimulated by Mg++ (Mg++-ATP-ase), alkaline phosphatase (AP), and 5'nucleotidase (5'Nt), a considerable damages begin to appear in the 15th d of life whereas in the case of acid phosphatase (AcP) already in the 1st d of life whereas in the case of acid phosphatase (AcP) already in the 1st d of life. These damages increase with age reaching their maximum in the 45th d of life.

5'-Nucleotidase↗
PubMed1998

Biochemical properties of 5'-nucleotidase from mouse skeletal muscle.

Ecto-5'-nucleotidase (eNT) from mouse muscle has been purified after extraction with detergent followed by chromatography on concanavalin A- and AMP-Sepharose. Three fractions were recovered: UF was NT non-retained in immobilised AMP; F-I was bound enzyme eluted with beta-glycerophosphate, and F-II was bound NT released with AMP. eNT was 80000-fold purified in F-II, this fraction showing proteins of 74, 68 and 51 kDa after immunoblotting. NT in UF migrated at 6.7S after centrifugation in sucrose gradients with Triton X-100, the peak being split into two of 6.7S and 4.4S in gradients with Brij 96. Ecto-NT in F-I or F-II migrated at 5.8S in Triton X-100-, or 4.4S in Brij 96-containing gradients. The hydrodynamic behaviour, concentration in Triton X-114, binding to phenyl-agarose, and sensitivity to phosphatidylinositol-specific phospholipase C revealed that enzyme forms in F-I or F-II were amphiphilic dimers with linked phosphatidylinositol residues, whilst most of NT forms in UF were hydrophilic dimers. A zinc/protein molar ratio of 2.2 was determined for eNT in F-II. NT activity was decreased in assays made in imidazole buffer, and was partly restored with 10 microM Zn2+ or 100 microM Mn2+. In assays with Tris buffer, NT showed a Km for AMP of 12 microM, and was competitively inhibited by ATP or ADP.

5'-Nucleotidase↗