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PubMed1985

Erythrocyte pyrimidine 5'-nucleotidase activity in workers exposed to lead, mercury or cadmium.

The erythrocyte pyrimidine 5'-nucleotidase activity (P5N) was measured in workers exposed to lead, cadmium or inorganic mercury and the effect of lead on this enzyme activity was compared with that on the classical biological parameters (ALAD, ZPP, ALAU), reflecting the interference of this metal with the heme biosynthesis pathway. P5N is inhibited by lead but not by cadmium and mercury. The correlation coefficient between log P5N and lead in blood (PbB) amount to 0.79 (n = 278; PbB ranging from 4.9 to 73.5 micrograms/100 ml). The response of P5N to lead closely parallels that of ALAD.

5'-Nucleotidase↗
PubMed1983

Heterogeneity in 5'-nucleotidase activity of mouse peritoneal macrophages. An EM-cytochemical and biochemical study.

After stimulation of the mouse peritoneal cavity with newborn calf serum (NBCS), four types of monocyte and macrophage were distinguished on the basis of peroxidase (PO) patterns. Cytochemically, these cells showed strong heterogeneity in 5'-nucleotidase (5'N) activity. Monocytes and monocyte-derived macrophages with PO activity in granules lacked 5'N activity. Resident macrophages (with PO activity in RER and nuclear envelope) generally had significant 5'N activity on the plasma membrane, the pattern showing close correlation with the biochemical findings. The group of PO-negative macrophages comprised both 5'N-negative and 5'N-positive cells. These findings suggest two possibilities, i.e., that monocytes (5'N-)transform via PO-negative cells (5'N -/+) into resident macrophages (5'N +), or that the monocytes and monocyte-derived macrophages and the resident macrophages represent separate lineages. The fourth type of macrophage, the exudate-resident cell (with PO activity both in granules and in the RER and nuclear envelope), occurred only in low numbers and very late after NBCS stimulation, and is therefore considered not to be a transitional cell between monocytes and resident macrophages.

5'-Nucleotidase↗
PubMed1984

Ultrastructural studies of concanavalin A receptors and 5'-nucleotidase localization in normal and injured mouse cerebral microvasculature.

Plant lectin concanavalin A conjugated with ferritin (Con A-F) injected i.v. was used for the detection of the specific monosaccharide residues (alpha-D-mannosyl and alpha-D-glucosyl) on the luminal surface of endothelial cells (ECs) in brain micro-blood vessels (MBVs). Both normal mice and animals with mechanically damaged blood-brain barrier (BBB) were used in this study. In addition, the activity of 5'-nucleotidase (5'N), the putative receptor for Con A, was studied cytochemically. Various methodologic experiments indicated that the reaction product formed on the luminal plasmalemma of ECs after incubation of samples in the cytochemical medium for the detection of 5'N activity results from the action of unspecific phosphatase hydrolyzing both specific and nonspecific substrates. The abluminal side of the wall of MBVs seems to be a major location of 5'N activity. Thus, no correlation between cytochemically demonstrable 5'N activity and Con A receptor sites on the luminal surface of ECs was noted. After damage of the BBB, extensive internalization of the luminal plasmalemma forming the limiting membranes of pinocytotic vesicles, vacuoles, and endothelial channel-like structures was observed. This process was represented by a relatively rapid translocation of Con A receptors from luminal surface into the interior of the ECs and to the abluminal side of the vessel wall.

5'-Nucleotidase↗
PubMed1983

5'-Nucleotidase activity in subjects with abnormal lymphocyte function.

5'-Nucleotidase (5'N) activity was determined in lymphocytes from patients with immunodeficiency diseases and in T-lymphocyte subpopulations from normal subjects. Cells from two patients with DiGeorge syndrome, with normal levels of B cells, and one patient with partial DiGeorge syndrome were found to have diminished 5'N activity. Utilizing monoclonal antibodies to deplete T-lymphocyte subpopulations, we found similar levels of 5'N in the cells remaining after depletion of OKT4- or OKT8-positive cells when 5'N values were determined after overnight incubation. If 5'N activity was determined on the day of the fractionation, however, OKT4-depleted cells had approximately threefold greater enzyme activity. These studies indicate that 5'N activity may vary in T lymphocyte subpopulations depending upon cell culture conditions. Diminished levels of 5'N activity are seen in patients with abnormal T-lymphocyte differentiation, as well as abnormalities of B-lymphocyte differentiation.

5'-Nucleotidase↗
PubMed1986

Kinetics of the 5'-nucleotidase and the adenosine deaminase in subcellular fractions of rat brain.

Suspensions of rat brain microsomes, synaptosomes, and synaptic vesicles were able to convert adenosine to inosine by means of adenosine deaminase. Isosbestic points of this transformation, at 222, 250 and 281 nm, remained unchanged with time-course. This fact suggests that adenosine deaminase (ADA, E.C. 3.5.4.4) is located on the surface of the vesicles whereas purine nucleoside phosphorylase (PNP, E.C. 2.1.2.4) is located inside the vesicles. Kinetic parameters of the particulate 5'-nucleotidase (5'N, E.C. 3.1.3.5) and adenosine deaminase were analogous to those of the cytosolic enzymes. These results suggest that soluble and particulate enzymes represent different pools of the same molecular species.

5'-Nucleotidase↗
PubMed1988

Localization of 5'-nucleotidase in bovine brain myelin fraction and myelin subfractions.

Purified myelin from fresh calf brain white matter was subfractionated in a discontinuous sucrose gradient; significant recovery of protein and 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNP) and 5'-nucleotidase (5'N) activities occurred in all three obtained subfractions, the highest recovery being in the light subfraction; highest 5'N and CNP specific activities were in medium myelin. Purified myelin was also subfractionated in a continuous sucrose gradient, with a similar localization of protein; CNP activity and 5'N activity maxima suggest that myelin may be a predominant locus of 5'N in bovine brain white matter. Freezing of brain white matter caused an increase in protein and in CNP and 5'N total activity recoveries in denser myelin subfractions. Cytochemistry showed the reaction product of 5'N in the whole myelin fraction to be associated with the innermost, outermost and medial compact myelin layers. Effects of non-ionic detergent (LUbrol WX) on 5'N activity were studied, and the results also suggest the intrinsic nature of 5'N as an ectoenzyme in myelin membranes. Lubrol WX was viewed as an advisable detergent for the stimulation of myelin 5'N activity, but not for the solubilization of this enzyme.

5'-Nucleotidase↗
PubMed1984

Cytochemical localization of 5'-nucleotidase in guinea-pig sympathetic ganglia.

Cytochemical techniques were used to study the localization of 5'-nucleotidase in sympathetic ganglia of the guinea-pig. Enzymatic activity was revealed in plasma membranes. Both the neuronal and satellite cell membranes contained the enzyme. Most of the activity was seen in the membrane of the satellite cells and this was interpreted to indicate a high level of purine utilization by these cells. The neurons displayed enzymatic activity in the membranes of non-specialized neuronal boundaries as well as at synapses.

5'-Nucleotidase↗
PubMed1985

Cytochemical localization of 5'-nucleotidase in the enteric ganglia and in smooth muscle cells of the guinea-pig.

Cytochemical techniques were used to study the localization of 5'-nucleotidase in the enteric ganglia and in smooth muscle cells of the guinea-pig ileum, iris and vas deferens. Enzymatic activity was revealed in plasma membranes and caveolae of smooth muscle cells and in neurons and neuroglia of the enteric ganglia. The strongest activity was seen in the membrane of the smooth muscle cells, especially the caveolae intracellulares, and this was interpreted to indicate a high level of purine utilization and involvement in calcium translocation by these cells. The ganglia displayed enzymatic activity in the membranes of non-specialized neuron-to-glia boundaries as well as at some synaptic specializations. This finding is consistent with a possible release of adenine nucleotides within the ganglia.

5'-Nucleotidase↗
PubMed1986

Determination of erythrocyte pyrimidine 5'-nucleotidase activity by 31P nuclear magnetic resonance: comparison of normal controls and multiple sclerosis patients.

A technique to assay erythrocyte pyrimidine 5'-nucleotidase activity in situ using 31P nuclear magnetic resonance spectroscopy is presented. The assay is chemically specific, simple and applicable to untreated lysates. A comparison of enzyme levels in normal controls and in multiple sclerosis patients employing the assay yielded no significant differences between both groups. Difficulties encountered in the quantitative analysis of the assay using 1H-NMR spectroscopy are briefly discussed.

5'-Nucleotidase↗
PubMed1986

Detection of pyrimidine 5'-nucleotidase deficiency using 1H- or 31P-nuclear magnetic resonance.

We describe here a further Japanese family with pyrimidine 5'-nucleotidase (P5'N) deficiency diagnosed using a nuclear magnetic resonance (NMR) spectrum, in Kumamoto prefecture where two families having the disease have been reported before. The specific spectra in 1H-NMR of P5'N deficient erythrocytes were due to three methyl protons of CDP-choline at 3.22 ppm and to H-2, H-8 and ribose-1' of pyrimidine nucleotide phosphate(s) in the lower fields (at 5.82 and 8.00 ppm). The other specificities in 31P-NMR spectra were due to CDP-choline, CDP-ethanolamine and UDP-glucose. Those spectra were not detected in other types of hemolytic anemia.

5'-Nucleotidase↗
PubMed1985

Adenosine uptake in pyrimidine 5'-nucleotidase deficient human erythrocytes via a high affinity transport system.

Using a pulse-labeling technique, 14C-adenosine uptake into pyrimidine 5'-nucleotidase (P5N) deficient erythrocytes (RBC) was found to be impaired. The Lineweaver-Burk plot showed Km values of 2.0 X 10(-3) mM and 0.2 X 10(-3) mM for normal RBC and P5N deficient RBC, respectively. These results indicate that P5N is one of regulators of the adenosine transport system and/or is associated with adenosine carrier protein.

5'-Nucleotidase↗
PubMed1980

Comparative study of effects of lead on the activity of erythrocyte pyrimidine 5'-nucleotidase and delta-aminolevulinate dehydratase in vivo and in vitro.

The effect of lead on the activities of erythrocyte pyrimidine 5'-nucleotidase (Py5N) and delta-aminolevulinate dehydratase (ALA-D) was studied in the mice which were given ad libitum a drinking water containing lead of 10, 50 and 250 ppm, for 27 days. The erythrocyte Py5N activity was not decreased in all groups of lead-exposed mice. However, the erythrocyte ALA-D activity was markedly decreased in the groups exposed to 50 and 250 ppm lead. These data indicate that erythrocyte ALA-D is more sensitive than Py5N to lead in vivo. On the other hand, from the in vitro study, it was demonstrated that the human erythrocyte Py5N is moderately inhibited by zinc and tin, and markedly by mercury, cadmium, silver, copper, and lead, at 10(-4) molar concentrations. In addition, it was observed that the erythrocyte Py5N is most remarkably inhibited by mercury while the ALA-D by lead, among metals tested.

5'-Nucleotidase↗
PubMed1985

A continuous spectrophotometric assay for pyrimidine-5'-nucleotidase.

A simple method is presented for the determination of pyrimidine-5'-nucleotidase activity using a continuous spectrophotometric assay system. Activity is determined by measuring inorganic phosphate generation using a linked indicator system that produces uric acid in the presence of inosine, purine nucleoside phosphorylase, and xanthine oxidase. This method has several advantages over any of the methods currently in use.

5'-Nucleotidase↗
PubMed1985

The membrane-bound alkaline phosphatase and 5'-nucleotidase activities of vegetative cells of Dictyostelium discoideum.

Earlier reports suggested that the adenosine monophosphate (AMP)- and the p-nitrophenyl phosphate (pNPP)-hydrolyzing activities of Dictyostelium discoideum membrane preparations are due to different proteins. These results have been apparently contradicted by the recent purification to homogeneity of the two activities from culmination phase cells as a single protein [D. R. Armant and C. L. Rutherford (1981) J. Biol. Chem. 256, 12710-12718]. Results presented here from studies on the activities of vegetative cells support the concept of a single protein. Nondenaturing sodium dodecyl sulfate-polyacrylamide gel electrophoresis of Triton X-100 extracts of cell membrane preparations of D. discoideum showed identical migration of pNPPase and AMPase activities. Furthermore, the previously reported different pH optima of the two activities was due to the fact that pH optima are dependent upon the substrate concentration, and the selective solubilization of AMPase from membrane preparations by phospholipase C can probably be accounted for by the finding that phospholipase C preparations from the same commercial source contain 5'-nucleotidase activity. Moreover, there are alterations in the Km and the stability of both AMPase and pNPPase in a strain with a mutationally altered alkaline phosphatase, further supporting the concept that the two activities are due to a single protein. Both substrates serve as transphosphorylation donors demonstrating that the enzyme activity is mechanistically an alkaline phosphatase.

5'-Nucleotidase↗
PubMed1989

Activity of myelin membrane Na+/K+-ATPase and 5'-nucleotidase in relation to phospholipid acyl profiles, ganglioside composition and phosphoinositides in developing brains of undernourished rats.

The relationship between undernutrition-induced alterations in some myelin membrane-bound enzyme activities and phospholipid fatty acid composition of this membrane was ascertained in developing rat brains. Undernutrition was imposed in pregnant dams through gestation and lactation, (last 10 days of gestation, and through lactation) by feed restriction. Experimental groups of animals received 50% of the amount of diet consumed by controls. Pups born to these mother rats were killed at day 7, 14 or 21 of postnatal age. Myelin membrane was isolated from the major regions of the brain, and analysed for phospholipid fatty acid profiles, phosphoinositides and ganglioside species. While there were no diet-related differences in the activities of 5'-nucleotidase (EC 3.1.3.5), myelin phospholipids from cerebella and brain stems of experimental rats exhibited lowered proportions of the long-chain polyunsaturated fatty acids, C20:4 (n - 6) and C22:6 (n - 3) concomitant with elevated activities of ouabain-sensitive Na+/K+-ATPase (EC 3.6.1.4). Levels of diphosphoinositide, triphosphoinositide and trisialogangliosides also decreased in myelin from brains of experimental animals. These results suggest a relationship between myelin phospholipid fatty acid profiles as indicators of membrane unsaturation, and the possibility of allosteric modification of Na+/K+-ATPase activity.

5'-Nucleotidase↗
PubMed1983

Properties and sidedness of 5'-nucleotidase in rat red cell ghosts.

The occurrence of a Mg++-activated 5'-AMPase activity in rat ghosts is demonstrated. This activity is inhibited by the alpha, beta-methyleneadenosine 5'-diphosphate, a specific inhibitor of 5'-nucleotidase. The enzyme has an apparent Km of approximately 90 microM, and is located on the exterior side of the plasma membrane.

5'-Nucleotidase↗
PubMed1980

Electrophoretic and kinetic studies of human erythrocytes deficient in pyrimidine 5'-nucleotidase.

A new variant of hereditary hemolytic anemia due to erythrocyte pyrimidine 5'-nucleotidase deficiency was found in Japan. Biochemical parameters such as the Michaelis constant, thermostability, electrophoresis and pH curve were studied. The variant showed a high Michaelis constant for cytidine 5'-monophosphate, no thermolability, slower electrophoretic mobility and abnormal optimum pH. The results strongly suggest that the mechanism of this enzyme deficiency is due to a structural gene mutation.

5'-Nucleotidase↗