SEARCH · PubMed Health

Results for “NUCLEOTIDASES”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16Linked to original sources

PubMed1985

The presence and orientation of ecto-5'-nucleotidase in rat liver lysosomes.

Purified rat liver lysosomes contained 5'-nucleotidase activity which was 92 +/- 2% [4]latent. This latency was lost in response to a permeant sugar at a similar rate to that of the lysosomal marker enzyme beta-N-acetylglucosaminidase indicating that the 5'-nucleotidase was genuinely located in the lysosome and not a plasma membrane contaminant. Lysosomal 5'-nucleotidase exhibited the following properties characteristic of ecto-5'-nucleotidase inhibition by specific polyclonal antibodies: binding to a monoclonal antibody; inhibition by 1 mmol/1 alpha beta-methylene ADP; immunoreactive subunits of 70 and 38 kDa. Lysosomes in addition contained immunoreactive species of intermediate molecular mass.

5'-Nucleotidase↗

PubMed1985

Redox-dependent activation of 5'-nucleotidase in rat liver plasma membranes.

Addition of NADH, but not NAD+ or NADPH, to rat liver plasma membranes resulted in the increase of their 5'-nucleotidase activity. NADH-dependent activation of 5'-nucleotidase was significantly suppressed by atebrine, an inhibitor of NADH dehydrogenase of plasma membranes, and completely abolished by 2,4-dinitrophenol (2 X 10(-4)M) and Triton X-100 (2%). Inhibitors of electron transfer in the mitochondrial respiratory chain, rotenone and potassium cyanide, failed to affect 5'-nucleotidase activity in both the presence and absence of NADH. The data obtained give reasons to suggest a redox-dependent mechanism of 5'-nucleotidase activation in rat liver plasma membranes.

2,4-Dinitrophenol↗

PubMed1988

Insulin-induced decrease in 5'-nucleotidase activity in skeletal muscle membranes.

Insulin releases inositol phosphoglycans from myocytes in culture [(1986) Science 233, 967-972], which display insulinomimetic activity. Because 5'-nucleotidase is anchored to the membrane through inositol-containing phospholipid glycans, we investigated whether insulin could release the enzyme from the membrane. Membranes prepared from hindquarter muscles of rats perfused with insulin showed a 23% decrease in 5'-nucleotidase activity. Isolated membranes from muscle exposed to insulin in vitro also showed a small but reproducible decrease (9%) in 5'-nucleotidase activity relative to unexposed controls. Phospholipase C from Staphylococcus aureus released 60% of the membrane-bound 5'-nucleotidase. We propose that insulin may activate an endogenous phospholipase C that cleaves phospholipid-glycan-anchored proteins.

5'-Nucleotidase↗

PubMed1986

Concanavalin A induced inhibition of 5'-nucleotidase from guinea pig skeletal muscle and bull seminal plasma: a comparative study.

Both purified and membrane-bound 5'-nucleotidases (EC 3.1,3.5) from guinea pig skeletal muscle and bull seminal plasma are inhibited by Concanavalin A (Con A). 5'-Nucleotidase purified from skeletal muscle is inhibited by Con A by an apparent uncompetitive process (K'i = 160 nM), while the lectin inhibits the particulate enzyme by an apparent non-competitive process (Ki = K'i = 50 nM). 5'-Nucleotidase purified from bull seminal plasma is inhibited by Con A by an apparent non-competitive process (K'i = Ki = 270 nM), while the membrane-bound enzyme is subjected to a mixed type inhibition by the lectin (K'i greater than Ki; 30 and 14 nM, respectively). The enzyme purified from skeletal muscle exhibits a significant cooperativity in the interaction with Con A. The inhibition of bull seminal plasma particulate 5'-nucleotidase brought about by Con A is not completely reversed by addition of alpha-methyl-D-mannoside.

5'-Nucleotidase↗

PubMed1983

Lymphocyte enzyme activities in East African blacks: decrease in 5'nucleotidase and possible relation to immunosuppression.

Microanalysis of subcellular organelle marker enzymes was applied to cryopreserved lymphocytes (obtained and processed in the field) from East African blacks with moderate to severe malnutrition and subject to locally endemic parasitic and infectious diseases. An initial study demonstrated that activities of these enzymes, with the partial exception of catalase, were stable to cryopreservation. Cryopreserved and thawed lymphocyte specimens (1 to 3 X 10(6) viable cells) from 26 Africans and 20 Caucasian controls were studied. There was a highly significant decrease in 5'nucleotidase activity in these African subjects. Activity of another plasma membrane enzyme, gamma-glutamyl transferase, and of marker enzymes for other intracellular organelles, was not significantly different between the two groups, indicating that the nucleotidase alteration is highly specific. 5'Nucleotidase activity in a group of 17 East African blacks of high socio-economic status lay between the values obtained in the other two groups and was not significantly different from either. Further studies on 5'nucleotidase showed no evidence that the enzyme is functionally different in Africans. The differences in activity of this enzyme in Africans may reflect the known immuno-suppressive effects of infectious disease and malnutrition or may have a genetic basis which may in turn be associated with the pathogenesis of secondary immunodeficiency.

5'-Nucleotidase↗

PubMed1980

Influence of age on 5'-nucleotidase in plasma membranes isolated from rat liver.

Studies were carried out to determine the kinetic properties of 5'-nucleotidase from liver plasma membranes in rats of different ages; four groups were examined, namely rats 25 +/- 2, 60 +/- 5, 230 +/- 15 and 525 +/- 20 days old. The 5'-nucleotidase showed minimum Vmax values in young rats; differences in this kinetic parameter were not detected among the other groups. However, the Km values increased during growth and development, declined in young animals and increased again in the middle-aged. Arrhenius plots of the 5'-nucleotidase activity showed a single break at aroung 22 degrees C in developing the middle-aged animals; the break temperature decreased to 17 degrees C in the rats 230 +/- 15 days old. The pH-Vmax and pH-Km curves showed a maximum at pH 7.6 at all ages. Lipid analysis of membrane preparations was carried out. Phospholipid composition did not change markedly with age. The cholesterol level decreased between 25 +/- 2 and 60 +/- 5 days. The degree of saturation of fatty acids seemed to increase in the same period, but reached the lowest value in the young rats. The results indicate that either sphingomyelin or other phospholipids do not affect the isothermal kinetics of 5'-nucleotidase during development and aging. Furthermore, phospholipid polar groups as well as the cholesterol and fatty acids of the bulk lipid phase modulate the membrane fluidity in the same way at different ages. Finally, the modifications of the Km with age cannot be correlated with changes in the surface charge.

5'-Nucleotidase↗

PubMed1988

Role of inositol starvation on ecto-5'-nucleotidase activity during mitogen-induced lymphocyte activation.

Cell-surface 5'-nucleotidase was assayed by incubating intact cells with 5' [3H]AMP in iso-osmotic buffer and measuring [3H]adenosine production. The activity of cell surface 5'-nucleotidase in small resting lymphocytes and in cells of the B cell line BCL1 was 5.7 and 1.1 nmol/min/mg protein respectively at 37 degrees C. The 5'-nucleotidase was inhibited by Concanavalin A and anti-IgM, the inhibition by anti-IgM being reversible. Incubating the lymphocytes in the presence and absence of mitogens in inositol-free medium for 15 min, 60 min, and 24 h had no effect on 5'-nucleotidase activity. The reaction product adenosine as well as adenine nucleotides were shown to inhibit mitogen-induced proliferation.

5'-Nucleotidase↗

PubMed1986

5'-Nucleotidase of cerebellar molecular layer: reduction in Purkinje cell-deficient mutant mice.

The molecular layer of the cerebellar cortex contains high levels of the enzyme 5'-nucleotidase (EC 3.1.3.5), localized predominantly to Bergmann glia. In the present study, histochemical methods have been employed to examine the distribution of cerebellar 5'-nucleotidase in mice of two separate mutant strains in which Purkinje cells are eliminated selectively. In homozygous 'Purkinje cell degeneration' (pcd) and 'nervous' (nr) mice, molecular layer 5'-nucleotidase is greatly reduced and residual enzyme activity in colocalized with surviving Purkinje cells. These results suggest strongly that the expression of 5'-nucleotidase activity by Bergmann glia is under the inductive influence of their associated Purkinje cells.

5'-Nucleotidase↗

PubMed1989

Stimulation by glycerate 2,3-bisphosphate: a common property of cytosolic IMP-GMP 5'-nucleotidase in rat and human tissues.

Glycerate 2,3-bisphosphate, a potent stimulator of the cytosolic 5'-nucleotidase which preferentially hydrolyzes IMP and GMP in human erythrocytes (Bontemps et al., 1988, Biochem. J. 250, 687-696), also stimulates the dephosphorylation of IMP in cytosol fractions of rat heart, liver, brain, kidney, spleen and erythrocytes, and of human polymorphonuclear leucocytes, mixed peripheral blood lymphocytes, platelets and fibroblasts. Depending on the cell type, stimulation by 5 mM glycerate 2,3-bisphosphate varied from 1.5- to 12-fold. Where investigated, glycerate 2,3-bisphosphate had an approx. 5-fold higher affinity for the enzyme than its other stimulator, ATP. These observations provide a useful tool to distinguish IMP-GMP 5'-nucleotidase from other 5'-nucleotidases, and suggest a common origin of the cytosolic IMP-GMP 5'-nucleotidase in various tissues.

2,3-Diphosphoglycerate↗

PubMed1990

5'-nucleotidase from bull seminal plasma, chicken gizzard and snake venom is a zinc metalloprotein.

Using flame atomic absorption spectrometry the tight association of zinc to three different purified 5'-nucleotidases at a molar ratio of 2 could be proven. These 5'-nucleotidases purified from bull seminal plasma (BSP), chicken gizzard (CG) and snake venom (SV) are thus zinc metalloproteins. Removal of zinc results in the loss of their AMPase activity, which could be fully restored after readdition of zinc at a molar ratio of 2, for BSP and CG, and 1.5, for SV 5'-nucleotidase. Reactivation of their AMPase activity after the removal of zinc could also be obtained by addition of cobalt and copper ions, which were found to also bind with a molar ratio of 2 to the three 5'-nucleotidases tested.

5'-Nucleotidase↗

PubMed1986

Membrane-bound 5'-nucleotidase inhibitor in Ehrlich ascites tumour cells and newborn mouse liver.

5'-Nucleotidase activity in Ehrlich ascites tumour cells was undetectable. The cell homogenate, when mixed with adult mouse liver homogenate, inhibited the 5'-nucleotidase activity of the latter, without affecting its p-nitrophenyl phosphate-hydrolysing activity. The inhibitor activity was enriched (6.8-fold) in a membrane fraction which was enriched in (Na+ + K+)-ATPase (14-fold) and alkaline phosphatase (8-fold). 5'-Nucleotidase activity in this membrane fraction could be detected only after separating the inhibitor activity from the enzyme on Sephadex G-50. The inhibitor activity was decreased by 27% when heat-treated, 33% when treated with 6 M urea and was almost completely lost when treated with trypsin. It was dialysable from a tubing with a molecular exclusion limit of 10,000, but was retained in a tubing with an exclusion limit of 3000. From these results we conclude that a small molecular weight protein inhibitor(s) of 5'-nucleotidase is present in the plasma membrane of Ehrlich ascites tumour cells. Also, the presence of such an inhibitor in the newborn mouse liver but not in the adult liver suggests that it may have some role in cellular ageing and cancer.

5'-Nucleotidase↗

PubMed1983

Serum 5'-nucleotidase: automation of a manual assay and brief observations on values in patients with breast cancer.

We have modified a manual assay method for the determination of serum 5'-nucleotidase so that the reaction product, phosphate, is assayed colorimetrically using a continuous flow system. The contribution of non-specific phosphatase enzymes is assessed in the presence of nickel ions which specifically inhibit 5'-nucleotidase. The detergent sodium lauryl sulfate is used to eliminate the need for deproteinization in the phosphate assay. We have measured 5'-nucleotidase activity in the sera of 123 breast cancer patients and correlated our data with the patients' clinical status. Receiver operating characteristic curve analysis showed the most advantageous cut-off point for indication of secondary spread to be 10 U/L. Using this cut-off point, 14% of patients who were clinically free of disease and 35% of patients with disease clinically present had elevated 5'-nucleotidase activity.

5'-Nucleotidase↗

PubMed2000

Simultaneous assessment of ecto- and cytosolic-5'-nucleotidase activities in brain micropunches.

We propose a new methodology for simultaneous assessment of ecto- and cytosolic-5'-nucleotidase that can be utilized in brain to measure the activity of these enzymes in micropunches of tissues. It is based on the differential sensitivity of both enzymes to alpha,beta-methyleneadenosine 5'-diphosphate (AMP-CP) and the requirements for magnesium as a co-factor. The design of assay protocol contains an internal validation by allowing comparisons between total level of 5'-nucleotidase activity with that calculated from the sum of individual activities of the ecto- and cytosolic-5'-nucleotidases. We have applied this new approach to assess the activity of ecto- and cytosolic-5'-nucleotidase in the brain regions relevant to sleep regulation. The level of both enzymes was significantly lower in the cerebral cortex than other brain regions tested.

5'-Nucleotidase↗

PubMed1984

Characterization of different molecular forms of 5'-nucleotidase in normal serum and in serum from cholestatic patients and bile-duct-ligated rats.

Serum 5'-nucleotidase in rat and man is derived from the plasma membrane rather than the cytosol by the criteria of inhibition with [alpha beta-methylene]ADP and antisera. In individuals with cholestasis the serum enzyme is mainly present as a high-Mr form that in the presence of the zwitterionic detergent Sulphobetaine 14 has the electrophoretic characteristics of liver plasma-membrane ectoenzyme. A minor form of 5'-nucleotidase in cholestatic serum and all the enzyme in normal serum appears to be half the molecular size of the liver plasma-membrane ectoenzyme. 5'-Nucleotidase from both normal and cholestatic rat serum was found to contain a polypeptide chain of apparent Mr 70 000 by immunoblotting techniques. It is suggested that the major form of 5'-nucleotidase in cholestatic serum is an ectoenzyme dimer derived from liver plasma membrane. All of the enzyme in normal serum and some of the enzyme in cholestatic serum is present as an active monomer derived from the ectoenzyme dimer.

5'-Nucleotidase↗

PubMed1989

Disparate effects of dietary fatty acids on activity of 5'-nucleotidase of rat liver plasma membrane.

The effects of incorporation of dietary n-3 polyunsaturated fatty acids (PUFA) into rat liver plasma membrane on the activity of 5'-nucleotidase (EC 3.1.3.5) was studied. The membrane phospholipids from rats fed a diet containing 10% by weight menhaden oil (MO) for 3 wk contained more n-3 PUFA and less n-6 PUFA in phospholipids classes, i.e., 24% and 65% less linoleic and arachidonic acid in phosphatidylcholine, than in rats fed 10% coconut oil (CNO) diets. The specific activity of 5'-nucleotidase in n-3 PUFA-enriched hepatic plasma membranes was 1.6- to 2-fold higher than that in rats fed CNO or corn oil (CO). Lineweaver-Burk plots for 5'-nucleotidase in liver plasma membranes isolated from rats fed MO and CNO showed no significant differences in Km values but the Vmax was increased by 67% in MO-fed rats. Arrhenius plots showed a break point in 5'-nucleotidase activity at 28.3 degrees C and 30.8 degrees C in plasma membranes from MO- and CNO-fed rats, respectively. The implications of this in the generation of adenosine and its possible impact on physiological functions are discussed.

5'-Nucleotidase↗

PubMed1983

Carbonic anhydrase, 5'-nucleotidase, and 2',3'-cyclic nucleotide-3'-phosphodiesterase activities in oligodendrocytes, astrocytes, and neurons isolated from the brains of developing rats.

The activities of three myelin-associated enzymes, carbonic anhydrase, 5'-nucleotidase, and 2',3'-cyclic nucleotide-3'-phosphodiesterase (CNP), were measured in oligodendrocytes, neurons, and astrocytes isolated from the brain of rats 10, 20, 60, and 120 days old. The carbonic anhydrase specific activity in oligodendrocytes was three- to fivefold higher than that in brain homogenates at each age, and, at all the ages, low activities of this enzyme were measured in neurons and astrocytes. The oligodendrocytes and astrocytes from the brains of rats at all ages had higher activities of the membrane-bound enzyme 5'-nucleotidase than was observed in neurons. In oligodendrocytes from 10- and 20-day-old rats, the 5'-nucleotidase activity was two-to threefold the activity in the homogenates (i.e., relative specific activity = 2.0-3.0), and the relative specific activity of this enzyme in the oligodendrocytes declined to less than 1.0 at the later ages, concomitant with the accumulation of 5'-nucleotidase in myelin. The CNP activity was always higher in oligodendrocytes than in neurons, but not appreciably different from that in astrocytes from 20 days of age onward. The relative specific activity of CNP was highest in the oligodendrocytes from 10-day-old rats but was lower, at all ages, than we had observed in bovine oligodendrocytes. These enzyme activities in oligodendroglia are quite different in amount and developmental pattern from those reported previously for myelin.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗

PubMed1980

Effect of surface modifiers on an ectoenzyme: granulocyte 5'-nucleotidase.

Several agents that react with plasma membranes, namely the native lectins concanavalin A, Ricinus communis agglutinin, and wheat germ agglutinin, the modified lectin succinyl concanavalin A, and sodium meta-periodate, inhibited the ecto-5'-nucleotidase of intact guinea pig granulocytes. Stimulation of the enzyme was not observed at any lectin concentration. Inhibition by native lectins could be blocked or reversed by appropriate competing hapten sugars. In the case of concanavalin A, reversal could be achieved at 37 degrees C, but not at 5 degrees C. When lectins were used in combination with each other, the effects were found to be largely independent. However, when concanavalin A and R. communis agglutinin were applied together, complications arose because the former lectin binds to the latter as well as to the cell surface. To avoid some of the complexities inherent in studying intact cell 5'-nucleotidase and to gain additional information about the system, two broken cell enzyme preparations were also examined. The enzyme of plasma membrane-enriched fractions was inhibited by all five agents mentioned above. 5'-Nucleotidase solubilized in sodium deoxycholate was inhibited by the four lectins but stimulated by periodate. The effects of the surface modifiers on kinetic data for all three enzyme preparations are consistent with the hypothesis that direct interactions with the enzyme molecule give rise to changes in Vmax; interactions at membrane sites other than 5'-nucleotidase itself could cause increases in apparent Km values. Effects of interactions of ectoenzymes with plant lectins may serve as models for phenomena that result from cell-cell interactions or from interactions of animal cells with lectin-like components of the cellular environment.

5'-Nucleotidase↗

PubMed1963

BACTERIAL NUCLEOTIDASES.

Kohn, J. (Queen Mary's Hospital, London, England) and J. L. Reis. Bacterial nucleotidases. J. Bacteriol. 86:713-716. 1963.-The 3- and 5- nucleotidase activity in various bacterial species was investigated. Both enzymes were found in bacterial extracts in varying proportions. The nucleotidases were found to be very active in Proteus vulgaris, in which organism they were studied in detail. The relative activities, the pH optima, and the effect of metal ions were investigated. It was concluded that bacterial 3- and 5-nucleotidases are distinct and separate enzymes.

Bacillus cereus↗