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

---

Query: EC:3.1.3.5 (5'-nucleotidase)
3,167 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The behaviour of 5'-nucleotidase isoenzymes (ecto-5'-nucleotidase, e-Ns and c-N-II soluble 5'-nucleotidases) was studied in lymphocytes from patients with B-cell chronic lymphocytic leukemia. A strong reduction in ecto- and soluble activities was observed, although the pattern of the three 5'-nucleotidases did not always strictly overlap. A significant decrease (p<0.05) in ecto-5'-nucleotidase, e-Ns and c-N-II was found in B and T populations (B lymphocytes: 1.13, 0.88 and 1.26 nmol/h/10(6) cells versus 95.96, 9.64 and 13.73 nmol/h/10(6) cells in controls; T lymphocytes: 1.31, 0.23 and 0.06 nmol/h/10(6) cells versus 9.25, 1.31 and 2.10 nmol/h/10(6) cells in healthy subjects). The percentage of ecto-5'-nucleotidase-positive cells (CD73+) was reduced in leukemia patients, indicating a lower number of active molecules on the cell surface. The results of RT-PCR analysis showed that the ecto-5'-nucleotidase mRNA of leukemia patients was not defective.
...
PMID:Behaviour of human lymphocytic isoenzymes of 5'-nucleotidase. 965 Nov 14

Differences on 5'-nucleotidase activity in intact Rugli and BCS-TC2 cells (rat glioblastoma and human colon adenocarcinoma cell lines, respectively) are not due to differences in the characteristics of the ectoenzyme. A membrane-bound 5'-nucleotidase from BCS-TC2 cells has been purified to homogeneity with a high specific activity (130 U/mg), yielding a single 72-kDa band on SDS-PAGE. It is a metalloenzyme and, after inhibition by EDTA, its activity can be partially restored by divalent cations. The hydrolysis of the nucleosides 5'-monophosphate used as substrate follows Michaelis-Menten kinetics; ADP and concanavalin A are competitive and non-competitive inhibitors of the AMPase activity, respectively. This ecto-5'-nucleotidase is a high-mannose glycoprotein; deglycosylation converts the 72-kDa into a 59-kDa protein with a concomitant activity loss. The enzyme purified from BCS-TC2 cells shows similar characteristics from that previously isolated from Rugli cells; differences between them are mainly due to glycosylation. Polyclonal antibodies against 5'-nucleotidase from BCS-TC2 cells also show cross-reactivity with the enzyme from Rugli cells. When the ectoenzyme activity is measured in cells in culture, Rugli cells present a higher activity than BCS-TC2 cells however, they express very low amounts of ecto-5'-nucleotidase. Our results also show a reduction in protein level and enzyme activity associated with a decrease in the differentiation degree and an increase in tumorigenicity of human colon adenocarcinoma BCS-TC2 sublines.
...
PMID:Ecto-5'-nucleotidase from a human colon adenocarcinoma cell line. Correlation between enzyme activity and levels in intact cells. 978 49

Adenosine increases blood flow and decreases excitatory nerve firing. In the heart, it reduces rate and force of contraction and preconditions the heart against injury by prolonged ischemia. Based on indirect kinetic arguments, an AMP-selective cytosolic 5'-nucleotidase designated cN-I has been implicated in adenosine formation during ATP breakdown. The molecular identity of cN-I is unknown, although an IMP/GMP-selective cytosolic 5'-nucleotidase (cN-II) and an ecto-5'-nucleotidase (e-N) have been cloned. We utilized the high abundance of cN-I in pigeon heart to purify a 40-kDa subunit for partial protein sequencing and subsequent cDNA cloning. We obtained a full-length clone encoding a novel 40-kDa peptide, unrelated to cN-II or e-N, that was most abundant in heart, brain, and breast muscle. Immunolocalization in heart showed a striated cytoplasmic location, suggesting association with contractile elements. Transient expression in COS-7 cells, generated a 5'-nucleotidase that catalyzed adenosine formation from AMP, which was increased during ATP catabolism. In conclusion, the cloning and expression of cN-I provides definitive evidence of its ability to produce adenosine during ATP breakdown.
...
PMID:The mechanism of adenosine formation in cells. Cloning of cytosolic 5'-nucleotidase-I. 1036 22

Adenosine, derived from hydrolysis of 5'-AMP by 5'-nucleotidase activity, may be involved in coupling coronary blood flow to cardiac function and metabolism; it has been postulated as a cardioprotective substance in ischemic myocardium. The stimulation of beta-adrenergic receptors produces an increase in adenosine by 5'-AMP hydrolysis. In addition, it has been demonstrated that in Chagas' disease there is decreased cardiac perfusion. We show in this paper by histochemical and densitometric procedures that ecto-5'-nucleotidase activity increases in ventricles of acutely Trypanosoma cruzi-infected mice and that the density of beta-adrenergic receptors is significantly diminished with affinity similar to controls, showing that a compensatory mechanism was absent. The increase of ecto-5'-nucleotidase in heart myocytes from infected mice may produce cardioprotective adenosine that may be independent of beta-adrenergic function, based on the hypoperfusion conditions of acute chagasic cardiomyopathy.
...
PMID:Trypanosoma cruzi: increased 5'-nucleotidase activity associated with dysfunction of adrenergic receptors in acutely infected albino Swiss mice. 1057 39

Ecto-5'-nucleotidase is regarded as being the key enzyme in the formation of the neuromodulator adenosine from released ATP. However, the association of ecto-5'-nucleotidase with nerve terminals is not consensual. Only enzyme histochemical and biochemical studies, but not immunocytochemical studies, agree on a general synaptic location of the enzyme. To clarify this issue further we tested the effect of an antibody against ecto-5'-nucleotidase, previously used in immunocytochemical studies, on the activity of ecto-5'-nucleotidase in fractions of nerve terminals isolated from different areas of rat hippocampus. The specific activity of extracellular AMP catabolism was higher in synaptosomes from the CA3 area (0.81+/-0.06 nmol/min/mg of protein) than from synaptosomes from the CA1 area or the dentate gyrus or from the whole hippocampus (0.49-0.68 nmol/ min/mg of protein). The catabolism of AMP (10 microM) was equally inhibited (85-92%) in synaptosomes from whole hippocampus, CA1, CA3, or dentate gyrus by alpha,beta-methylene-ADP (100 microM) and equally unaffected by p-nitrophenyl phosphate (0.5 mM) or rabbit IgGs (100 microg/ml). However, the antiserum against ecto-5'-nucleotidase (100 microg/ml) inhibited extracellular AMP catabolism by 44% in CA3 synaptosomes but had little or no effect in synaptosomes from CA1, dentate gyrus, or whole hippocampus. A similar difference in the inhibitory potential of the antibody was observed between fractions of isolated 5'-nucleotidase binding to concanavalin A-Sepharose (70%) and fractions not retained by the lectin column (18%). Taken together, these results suggest that immunological isoforms of ecto-5'-nucleotidase exist in the rat hippocampal nerve terminals, with predominance in the CA3 area.
...
PMID:Immunologically distinct isoforms of ecto-5'-nucleotidase in nerve terminals of different areas of the rat hippocampus. 1061 37

Stimulation of endothelial cells from human umbilical vein by shear stress induced release of endogenous ATP which was accompanied by an extracellular increase in the activity of enzymes degrading both ATP (ATPases) and AMP (5'-nucleotidases). The activity of soluble ATPase was progressively increased from 1.62+/-0.27 to 12.7+/-1.0 pmoles ml(-1) h(-1) after 60 min of stimulation by shear stress. The rate of [(3)H]-ATP hydrolysis in the medium was inhibited by the purinergic agents suramin, Reactive blue 2 and pyridoxalphosphate-6-azophenyl-2'4'-disulphonic acid, and remained insensitive to the classic inhibitors of ion-pumping and intracellular ATPases. Shear stress also increased the activity of 5'-nucleotidase in the medium from 2.0+/-0.5 to 27.2+/-2.8 pmoles ml(-1) h(-1). When shear stress was applied after removal of ecto-5'-nucleotidase by phosphatidylinositol-specific phospholipase C, the release of 5'-nucleotidase was drastically reduced. These results show that soluble ATPase and 5'-nucleotidase which are released during shear stress are not released from an intracellular compartment together with ATP but have an extracellular origin.
...
PMID:Effect of shear stress on the release of soluble ecto-enzymes ATPase and 5'-nucleotidase along with endogenous ATP from vascular endothelial cells. 1069 91

5'-Nucleotidase, responsible for the conversion of adenosine-5'-monophosphate into adenosine, was purified from bovine brain membranes, and subjected to oxidative inactivation. The 5'-nucleotidase activity decreased slightly after the exposure to either glutathione or Fe2+. The glutathione-mediated inactivation of 5'-nucleotidase was potentiated remarkably by Fe2+, but not Cu2+, in a concentration-dependent manner. Similarly, glutathione exhibited a concentration-dependent enhancement of the Fe2+-mediated inactivation. In comparison, the glutathione/Fe2+ system was much more effective than the ascorbate/Fe2+ system in inactivating the enzyme. In support of an intermediary role of superoxide ions or H2O2 in the action of glutathione/Fe2+ system, superoxide dismutase and catalase expressed a substantial protection against the inactivation by the glutathione/Fe2+ system. Meanwhile, hydroxyl radical scavengers such as mannitol, benzoate or ethanol were incapable of preventing the inactivation, excluding the participation of extraneous hydroxyl radicals. Whereas adenosine 5'-monophosphate as substrate exhibited a modest protection against the glutathione/Fe2+ action, a remarkable protection was expressed by divalent metal ions such as Zn2+ or Mn2+. Structure-activity study with a variety of thiols indicates that the inactivating action of thiols in combination with Fe2+ resides in the free sulfhydryl group and amino group of thiols. Overall, thiols, expressing more inhibitory effect on the activity of 5'-nucleotidase, were found to be more effective in potentiating the Fe2+-mediated inactivation. Further, kinetic analyses indicate that Fe2+ and thiols inhibit the 5'-nucleotidase in a competitive or uncompetitive manner, respectively. These results suggest that ecto-5'-nucleotidase from brain membrane is one of proteins susceptible to thiols/Fe2+-catalyzed oxidation, and the oxidative inactivation may be related to the selective association of Fe2+ and thiols to the enzyme molecule.
...
PMID:Oxidative inactivation of brain ecto-5'-nucleotidase by thiols/Fe2+ system. 1107 66

We previously demonstrated that extracellular adenine nucleotides induced cyclic AMP elevation through local adenosine production at the membrane surface and subsequent activation of adenosine A(2A) receptors in NG108-15 cells. Furthermore, the adenosine formation was found to be mediated by an ecto-enzyme distinct from the ecto-5'-nucleotidase (CD73). In this study, we investigated the properties of the ecto-AMP phosphohydrolase activity in NG108-15 cells. NG108-15 cells hydrolyzed AMP to adenosine with the K:(M:) value of 18.8+/-2.2 microM and V(max) of 5.3+/-1.6 nmol min(-1) 10(6) cells(-1). This activity was suppressed at pH 6.5, but markedly increased at pH 8.5. The AMP hydrolysis was blocked by levamisole, an alkaline phosphatase (ALP) inhibitor. NG108-15 cells released orthophosphate from 2'- and 3'-AMP as well as from ribose-5-phosphate and ss-glycerophosphate, indicating that NG108-15 cells express ecto-ALP. The cyclic AMP accumulation induced by several adenine nucleotides was inhibited by levamisole, p-nitrophenylphosphate and ss-glycerophosphate, with a parallel decrease in the extracellular adenosine formation. Reverse transcriptase polymerase chain reaction analysis revealed that NG108-15 cells express mRNA for the tissue-nonspecific isozyme of ALP. These results demonstrate that AMP phosphohydrolase activity in NG108-15 cells is due to ecto-ALP, and suggest that this enzyme plays an essential role for the P1 antagonist-sensitive ATP-induced cyclic AMP accumulation in NG108-15 cells.
...
PMID:Ecto-alkaline phosphatase in NG108-15 cells : a key enzyme mediating P1 antagonist-sensitive ATP response. 1113 45

The mechanism underlying beta,gamma-methylene ATP (beta,gamma-MeATP)-induced cAMP elevation was investigated in rat glioma C6Bu-1 cells. Beta,gamma-MeATP increased forskolin-stimulated cAMP formation in a manner sensitive to both the P1 antagonist xanthine amine congener (XAC) and the P2 antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS). Adenosine deaminase (ADA; 1 U/mL), which abolished the adenosine-induced response, did not eliminate the beta,gamma-MeATP-induced response. However, combination of ADA with alpha,beta-methylene ADP (alpha,beta-MeADP), an ecto-5'-nucleotidase inhibitor, blocked the beta,gamma-MeATP-induced response. AMP, the substrate for ecto-5'-nucleotidase, also induced cAMP formation in a manner sensitive to XAC and alpha,beta-MeADP inhibition. However, the AMP-induced response was not blocked by PPADS. HPLC analyses revealed that adenosine was generated from beta,gamma-MeATP and AMP. In addition, alpha,beta-MeADP inhibited the conversion of beta,gamma-MeATP and AMP to adenosine, whereas PPADS blocked adenosine formation from beta,gamma-MeATP but not from AMP. [3H]Adenosine generated from [3H]AMP was preserved on the cell surface environment even in the presence of ADA. The mRNAs for ecto-phosphodiesterase/pyrophosphatase 1 (EC 3.1.4.1), ecto-5'-nucleotidase (EC 3.1.3.5) and adenosine A2B receptor were detected by RT-PCR. These results suggest that C6Bu-1 cells possess ecto-enzymes converting beta,gamma-MeATP to adenosine, and the locally accumulated adenosine in this mechanism efficiently stimulates A2B receptors in a manner resistant to exogenous ADA.
...
PMID:Beta,gamma-methylene ATP-induced cAMP formation in C6Bu-1 cells: involvement of local metabolism and subsequent stimulation of adenosine A2B receptor. 1115 59

Sertoli cells have been shown to be targets for extracellular purines such as ATP and adenosine. These purines evoke responses in Sertoli cells through two subtypes of purinoreceptors, P2Y2 and P A1. The signals to purinoreceptors are usually terminated by the action of ectonucleotidases. To demonstrate these enzymatic activities, we cultured rat Sertoli cells for four days and then used them for different assays. ATP, ADP and AMP hydrolysis was estimated by measuring the Pi released using a colorimetric method. Adenosine deaminase activity (EC 3.5.4.4) was determined by HPLC. The cells were not disrupted after 40 min of incubation and the enzymatic activities were considered to be ectocellularly localized. ATP and ADP hydrolysis was markedly increased by the addition of divalent cations to the reaction medium. A competition plot demonstrated that only one enzymatic site is responsible for the hydrolysis of ATP and ADP. This result indicates that the enzyme that acts on the degradation of tri- and diphosphate nucleosides on the surface of Sertoli cells is a true ATP diphosphohydrolase (EC 3.6.1.5) (specific activities of 113 +/- 6 and 21 +/- 2 nmol Pi mg(-1) min(-1) for ATP and ADP, respectively). The ecto-5'-nucleotidase (EC 3.1.3.5) and ectoadenosine deaminase activities (specific activities of 32 +/- 2 nmol Pi mg(-1) min(-1) for AMP and 1.52 +/- 0.13 nmol adenosine mg(-1) min(-1), respectively) were shown to be able to terminate the effects of purines and may be relevant for the physiological control of extracellular levels of nucleotides and nucleosides inside the seminiferous tubules.
...
PMID:Ectonucleotidase activities in Sertoli cells from immature rats. 1159 98


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---