Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “NUCLEOTIDASES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 685 records · Page 38Linked to original sources
PubMed1992

The distribution of A1 adenosine receptor and 5'-nucleotidase in pig brain cortex subcellular fractions.

Pig brain cerebral cortex was subfractionated by isopycnic centrifugation in sucrose gradients. In each subfraction the content of the agonist [3H]R-PIA binding, the activity of adenosine metabolizing enzymes (5'-nucleotidase and adenosine deaminase) and the activity of membrane marker enzymes were determined. The fractions were also examined by electron microscope. In general, the results suggest a widespread distribution of A1 adenosine receptors in membranes from different origins. Marker enzyme profile characterization indicated an enrichment of A1 adenosine receptor in pre-synaptic membranes isolated from the crude synaptosomal fraction (P2B subfraction) as well as in membranes of glial origin such as myelin. The receptor is also present in the endoplasmic reticulum and in membranes isolated from the microsomal fraction that seem to have a post-synaptic origin (P3B). In subfractions having a high content of adenosine receptor the equilibrium binding parameters were obtained as well as the proportion of high- to low-affinity sites. From the values of the equilibrium constants it was not possible to find differences between the receptor in the different subfractions. Analysis of the affinity state distribution showed a diminished percentage of high-affinity sites in fraction P3A, which can be accounted by the existence of myelin membranes; in contrast the percentage of high-affinity states was higher in P2 and P3B, indicating that in these fractions the receptor is present in synaptosomal membranes. The close correlation shown between the enzyme 5'-nucleotidase specific activity and the specific ligand binding distributions led us to postulate an important role for the enzyme in the regulation of adenosine action in pig brain cortex.

5'-Nucleotidase↗
PubMed1989

Deficiency of pyrimidine 5'-nucleotidase in human leukocytes.

Both erythrocytes and leukocytes from a patient with erythrocyte pyrimidine 5'-nucleotidase (P5N) deficiency were shown to contain increased amounts of pyrimidine nucleotides. These findings suggested that the leukocytes were also deficient for P5N. Measurement of the P5N activity in lysates from lymphocytes or granulocytes, in the presence of inhibitors for non-specific 5'-nucleotidase or alkaline phosphatase, indeed showed a deficiency for P5N in lymphocytes and granulocytes of the patient with erythrocyte P5N deficiency. However, the P5N deficiency in the leukocytes did not cause clinical disturbances in addition to the weak haemolytic anaemia.

5'-Nucleotidase↗
PubMed1980

5'-Nucleotidase activity in liver homogenates of rats treated with CCl4, colchicine, cycloheximide, emetine, ethanol, ethionine and 5-fluorotryptophan.

5'-Nucleotidase activity an enzyme marker of the plasma membranes, increases in female rat liver homogenates following ethionine administration, while homogenates from males show no changes. Treatment with CCl4, colchicine, cycloheximide, emetine, ethanol and 5-fluorotryptophan does not significantly modify the 5'-nucleotidase activity of liver homogenates of either female or male rats.

Animals↗
PubMed1992

Insulin-dependent release of 5'-nucleotidase and alkaline phosphatase from liver plasma membranes.

Insulin treatment of isolated liver plasma membranes induced the release of 5'-nucleotidase and alkaline phosphatase. This effect was maximal at physiological hormone concentrations, being 36% and 17% for 5'-nucleotidase and alkaline phosphatase respectively, and was fully mimicked by the phosphatidylinositol specific phospholipase C (PI-PLC), thus confirming the presence of a glycosylphosphatidylinositol anchoring-system for these exofacial enzymatic proteins. The complete inhibition of insulin dependent enzyme release by neomycin is strongly supportive of an involvement of membrane-located PI-PLC activity. In addition, the insulin-like effect on enzyme release induced by the GTP non-hydrolysable analog, GTP-gamma-S, and its sensitivity to the pertussis toxin are in favour of a mediatory role exerted by the G proteins system, in the transduction of some actions of insulin.

5'-Nucleotidase↗
PubMed1989

A study of 5'-nucleotidase activity in subcellular fractions of rat cerebellum after the administration of the convulsant 3-mercaptopropionic acid.

The activity of 5'-nucleotidase in cerebellum subcellular fractions after the administration of the convulsant 3-mercaptopropionic acid was studied. This membrane enzyme presented an increase in its activity in certain fractions containing nerve endings and microsomes (Mic20, Mic100) in seizure and postseizure periods. 5'-nucleotidase activity in nuclear and myelin fractions did not show differences between the control and treated fractions. On the other hand, a decreased activity in the crude mitochondrial fraction and in a nuclear subfraction was found. It is suggested that the changes in the enzyme activity in some cerebellum fractions might be related to structural alterations previously observed in this laboratory and with the anticonvulsant actions of adenosine.

3-Mercaptopropionic Acid↗
PubMed1998

Neutrophil 5-nucleotidase reaction in chronic myelogenous leukemia, myelofibrosis with myeloid metaplasia, and polycythemia vera.

A readable and reproducible 5-nucleotidase (5N) cytochemical reaction was developed for blood smear preparation, after modification of the technique of Wachstein and Meisel. The reaction was applied to normal polymorphonuclear neutrophils (NPN) and to neutrophils from patients with chronic myelogenous leukemia (CML), myelofibrosis with myeloid metaplasia (MMM), and polycythemia vera (PV). The following observations were made: (a) 5N was present in NPN, with a mean score of 83.2+/-15.7. (b) In patients with MMM and PV an increased 5N score was observed (mean score 111+/-63.8 and 178.3+/-83.3, respectively). (c) In CML the mean score was 4.9+/-2.2. (c) A statistical comparison of neutrophil 5-nucleotidase (N5N) between CML and MMM and PV patients demonstrated a highly significant difference (p<0.0001). In the present study, we showed that the N5N activity parallels that of NAP in chronic myeloproliferative disorders such as CML, MMM, and PV. It appears that, apart from the already known activity of NAP in myeloproliferative disorders, other enzymes (e.g., N5N) can present a similar behavior with increased or decreased activity.

5'-Nucleotidase↗
PubMed2000

Nicorandil increases adenosine 5'-monophosphate-primed interstitial adenosine via activation of ecto-5'-nucleotidase in rat hearts.

With the use of microdialysis techniques, we examined the effects of nicorandil, a hybrid of an ATP-sensitive K+ (K ATP) channel opener and a nitrate compound, on the production of interstitial adenosine in rat hearts in situ. The level of dialysate adenosine measured under a constant supply of adenosine 5'-monophosphate (AMP) reflected the activity of endogenous ecto-5'-nucleotidase. Nicorandil (0.3-3mM) increased the level of AMP (100 microM)-primed dialysate adenosine in a concentration-dependent manner, and this effect was completely abolished by the guanylate cyclase inhibitor, methylene blue (100 microM), but not by the K ATP channel blocker, glibenclamide (10 microM). Another K ATP channel opener, cromakalim (0.1-1mM), did not increase the production of AMP-primed dialysate adenosine. These results suggest that nicorandil increases the level of interstitial adenosine via cyclic guanosine monophosphate-mediated activation of ecto-5'-nucleotidase.

5'-Nucleotidase↗
PubMed2004

Trichomonas vaginalis: cytochemical localization of a NTPDase1 and an ecto-5'-nucleotidase and effects of adenine nucleotides on cellular viability.

Nucleoside triphosphate diphosphohydrolase 1 (NTPDase1), which hydrolyzes extracellular ATP and ADP, and ecto-5'-nucleotidase, which hydrolyzes AMP, are characterized for Trichomonas vaginalis. Ultrastructural cytochemical microscopy showed NTPDase1 and ecto-5'-nucleotidase activities on the surface of the parasites. High levels of extracellular adenine nucleotides and adenosine did not exert cytolytic effects in intact cells of T. vaginalis. Our results suggest that these enzymes are relevant for the survival of the parasite during exposure to extracellular nucleotides. Since the ecto-localization of these enzymes is essential for the maintenance of adenosine extracellular levels, this nucleoside could be important for the purine salvage pathway in the parasite.

5'-Nucleotidase↗
PubMed2006

Enhanced NTPDase and 5'-nucleotidase activities in diabetes mellitus and iron-overload model.

The activity of the enzymes NTPDase and 5'-nucleotidase was studied in both diabetes mellitus and an associated model of iron-overload. Rats were divided in five groups: citrate (CC), saline (S), diabetic (D), iron-overload (IO), and diabetic iron-overload (DIO). Diabetes was induced with alloxan (150 mg/kg), and iron-overload was induced with iron-dextran (10 intramuscular applications of +/-80 mg/kg). The enzymatic activities were evaluated in the platelets. The results demonstrated an increase in the activity of NTPDase with substrates ATP and ADP (60% and 120%, respectively; P<0.001), and 5'-nucleotidase (60%, P<0.001). This increase was more intense in the IO and DIO groups. The results obtained in vitro showed an activation in ATP, ADP, and AMP hydrolysis between 1 microM and 1,000 microM ferric nitrate concentrations, being more pronounced at 100 microM and decreasing at 1,000 microM. We concluded that diabetes mellitus in association with iron-overload increased the hydrolysis of adenine nucleotides in platelets, contributing to the abnormalities found in these pathological conditions.

5'-Nucleotidase↗
PubMed1986

In vitro inhibition of carrot chalcone synthase by 3'-nucleotidase: the role of the 3'-phosphate group of malonyl-coenzyme A in flavonoid biosynthesis.

In mixing experiments with extracts derived from two cell lines of Daucus carota tissue cultures with and without chalcone synthase activity, strong inhibition of chalcone synthase (CHS) became obvious. This inhibition was due to the presence of a heatlabile protein in extracts from cells devoid of CHS activity. This protein was partially purified and identified as 3'-nucleotidase (EC 3.1.3.6). Inhibition was also observed in the presence of purified 3'-nucleotidase from Lolium multiflorum. The phosphate group in the 3'-position of adenosine, a part of the CoA thioester substrates of CHS, was hydrolyzed by this enzyme. The dephosphorylated form of malonyl-CoA was no longer a substrate, whereas 4-coumaryl-3'-dephospho-CoA as well as 4-coumaryl-CoA was still able to act as a primer for the CHS reaction. Further studies showed that malonyl-3'-dephospho-CoA was an efficient CHS inhibitor. On the other hand, CoA-SH lost its inhibitory activity after dephosphorylation in the 3'-position. These results are discussed with respect to the mechanism of chalcone synthesis.

Acyl Coenzyme A↗
PubMed1991

Nucleoside phosphotransferase activity of human colon carcinoma cytosolic 5'-nucleotidase.

A cytosolic 5'-nucleotidase, acting preferentially on IMP and GMP, has been isolated from human colon carcinoma extracts. This enzyme activity catalyzes also the transfer of the phosphate group of 5'-nucleoside monophosphates (mainly, 5'-IMP, 5'-GMP, and their deoxycounterparts) to nucleosides (preferentially inosine and deoxyinosine, but also nucleoside analogs, such as 8-azaguanosine and 2',3'-dideoxyinosine). It has been proposed that the enzyme mechanism involves the formation of a phosphorylated enzyme as an intermediate which can transfer the phosphate group either to water or to the nucleoside. The enzyme is activated by some effectors, such as ATP and 2,3-diphosphoglycerate. Results indicate that the effect of these activators is mainly to favor the transfer of the phosphate of the phosphorylated intermediate to the nucleoside (i.e., the nucleoside phosphotransferase activity). This finding is in accordance with previous suggestions that cytosolic 5'-nucleotidase cannot be considered a pure catabolic enzyme.

2,3-Diphosphoglycerate↗
PubMed1975

5'-nucleotidase: an ecto-enzyme of frog skeletal muscle.

Using 1-4C-labeled AMP and IMP as substrates, 5'-nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) activity was detected at the external surface of frog skeletal muscle with the active site facing toward the extracellular space. The enzyme was firmly bound to the muscle membrane. Its activity was dependent on Ca2+ or Mg2+ and was inhibited by non-radioactive ribonucleoside 5'-monophosphates, or theophylline, while adenosine 3'-monophosphate and p-nitrophenylphosphate had little or no effect. 5'-Nucleotidase with similar properties was also found in the isolated plasma membrane fraction of the muscle.

Adenosine Monophosphate↗
PubMed1978

Properties of a non-specific nucleotidase in the membrane of rabbit red cells.

A non-specific nucleotidase was found in rabbit red blood cell membrane and, using 5'-AMP as substrate, several kinetic parameters for the enzyme were determined. Rabbit red cell ghosts catalyzed the hydrolysis of a wide spectrum of nucleoside 5'-, 3'- and 2'-monophosphates and a limited number of non-nucleotide substrates. All these activities were heat inactivated at the same rate, suggesting that they are the result of catalysis by the same enzyme. The nucleotidase was not dependent on K+ or Mg2+ and was also insensitive to ouabain. Its specific activity and other kinetic parameters were identical in preparation of membranes from both reticulocytes and the mature erythrocytes.

Animals↗
PubMed1996

Effects of P2-purinoceptor antagonists on degradation of adenine nucleotides by ecto-nucleotidases in folliculated oocytes of Xenopus laevis.

The aim of the present study was to examine the effects of a number of P2-purinoceptor antagonists on degradation of adenine nucleotides by Xenopus laevis oocyte ecto-nucleotidase. Folliculated oocytes readily metabolize all three naturally-occurring nucleotides, the order of preferential substrates being ATP >ADP > AMP. The degradation of ATP and ADP was decreased significantly in the presence of several P2X- and P2Y-purinoceptor antagonists, including suramin, PPADS, Cibacron blue, Coomassie Brilliant blue, Evans blue, Trypan blue, Congo red, and PIT (each compound was used at 100 microM). All these compounds inhibited the degradation of ATP by up to 60%, whereas the hydrolysis of ADP was inhibited by Congo red and PIT by 75-80%. In addition, DIDS (100 microM) and TNP-ATP (100 microM) selectively inhibited the breakdown of ATP, and sodium azide (10 mM) selectively inhibited the breakdown of ADP. The enzymatic breakdown of either ATP or ADP was unaffected by 8-pSPT (100 microM), an antagonist of P1-purinoceptors, or by oxidized ATP (100 microM), an antagonist of P2Z-purinoceptors. The degradation of AMP was prevented completely by PIT (100 microM) and ingibited significantly by Congo red (100 microM). In conclusion, the present study shows that most of currently available antagonists of P2-purinoceptors inhibit the enzymatic breakdown of extracellular ATP and ADP. The inhibitory effect on ecto-nucleotidase activity should be taken into account when these antagonists are used in pharmacological experiments.

Adenine Nucleotides↗
PubMed1980

Effects of thyroid state on brain development: beta-adrenergic receptors and 5'-nucleotidase activity.

The effect of thyroid status on beta-adrenergic receptor binding and 5'-nucleotidase activity was studied in the forebrain and the cerebellum of the rat during the first 5 postnatal weeks. The developmental increase in beta-adrenergic receptor binding was significantly depressed in thyroid deficiency in both the forebrain and the cerebellum. The effect was more pronounced in the cerebellum, where at day 35 the concentration and the total number of beta-adrenergic receptor sites were reduced by 35% and 50% respectively. In contrast, hyperthyroidism had no significant effect on the development of beta-adrenergic receptors in the brain. On the other hand, hyperthyroidism led to a sustained increase in the forebrain in the activity of 5'-nucleotidase, an enzyme which is also associated with plasma membranes and has been proposed to play some role in neurotransmission. In thyroid deficiency the enzyme activity was markedly depressed. The effect was significant from day 12 in the cerebellum and from day 21 in the forebrain, the maximal depression, at day 21, being 55% and 45% respectively. In comparison with these plasma membrane markers, the accretion of membranous proteins was less affected: although this was retarded in hypothyroidism and advanced in hyperthyroidism there was no residual effect at 35 days except those attributable to changes in organ size. The results indicated, therefore, that the biochemical specialization of cells, as reflected in certain plasma membrane constituents, are chatacteristically influenced in the developing brain by thyroid disorders.

Aging↗
PubMed1978

An improved method for the determination of human erythrocyte pyrimidine 5'-nucleotidase activity.

A radiometric method is described for measuring pyrimidine 5'-nucleotidase activity in human peripheral blood haemolysate. The substrate [14C]uridine monophosphate is converted to [14C]uridine. Two simple and rapid methods to isolate the product of the reaction employing either descending chromatography or elution from DEAE cellulose paper have been developed. With the described methods the specific activity of pyrimidine 5'-nucleotidase of human erythrocytes is 6.7 +/- 2.7 (+/- 1 S.D.) nmol/h/mg protein and this activity appears to be widely distributed in human tissue.

Carbon Radioisotopes↗
PubMed1978

A radioassay for pyrimidine-5'-nucleotidase activity.

A simple method for the determination of pyrimidine-5'-nucleotidase activity in red cells is described. The radioactive uridine released after incubation with [5-3H]] uridine 5-monophosphate (UMP) is separated on DEAE-cellulose paper and counted. This method does not require preliminary dialysis of the hemolysate and is 50-fold more sensitive than that based on the measurement of the inorganic phosphate released. One patient with pyrimidine-5'-nucleotidase deficiency was detected with this method.

Erythrocytes↗