Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: HUMANGGP:019083 (5'-nucleotidase)
 3,019 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Insulin receptor characteristics were examined in purified brush border membrane from the syncytiotrophoblast of the normal human placenta and quantified during membrane preparation. Insulin receptor concentration was enriched 10- to 15-fold in this preparation, and insulin receptor specific activity followed closely the enrichment values for microvillus plasma membrane markers, alkaline phosphatase, Ca2+- and Mg2+-ATPase, and 5'-nucleotidase during cell fractionation. Insulin receptor concentrations and marker enzyme analyses were compared in whole homogenate, mitochondrial, microsomal, and microvillus fractions, and these fractions were characterized by SDS-gel electrophoresis. Microvillus insulin receptor interactions were dependent on time, [125I]iodoinsulin concentration, protein, and unlabeled hormone concentrations. Competition studies with porcine insulin and [125I]iodoinsulin for this receptor revealed a curvilinear Scatchard plot. Insulinase was demonstrated at 37 C but was minimal at 24 C in the microvillus fraction. Electron microscopy of the microvillus membrane preparation revealed its composition to be mainly spherical closed membrane vesicles and brush border fragments. Sodium dodecyl sulfate polyacrylamide and isoelectric focusing gels of membrane fractions were compared. Actin was tentatively identified as a major microvillus membrane protein and was further fractionated: beta-Actin and gamma-actin were present in approximately equal concentrations. The localization of the insulin receptor in the microvillus brush border of the human placenta suggests that this receptor interacts with maternal, rather than fetal insulin.
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PMID:Characteristics of the microvillus brush border of human placenta: insulin receptor localization in brush border membranes. 75 22

1. 5'-Nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) from the cytosol of chicken liver has been purified 1860-fold with an overall yield of 20% by a combination of precipitation at pH 5.3, (NH4)2SO4 fractionation, calcium phosphate gel adsorption, phosphocellulose chromatography and gel filtration with Sephadex G-200. The enzyme has been shown to be highly purified, as judged by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. This is the first time it has been possible to obtain a purified 5'-nucleotidase from the cytosol of animal tissue. 2. An S20, W of 9.7 S for 5'-nucleotidase was obtained by the use of sucrose density gradient centrifugation and a Stokes radius of 5.1 nm was estimated by gel filtration techniques. From these values and the assumed partial specific volume of 0.725 cm3/g, the molecular weight of the enzyme was calculated to be 205 000. One major band, corresponding to a molecular weight of 51 000, was detected after sodium dodecyl sulphate-polyacrylamide gel electrophoresis indicating that the native enzyme was composed of four identical subunits. 3. Some properties of the purified enzyme, including pH optimum Mg2+ dependency and substrate specificity, resembled closely those of the partially purified enzyme from chicken liver acetone powder as reported by Itoh, R., Mitsui, A. and Tsushima, K. (1967) Biochim. Biophys. Acta 146, 151-159.
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PMID:Cytosol 5'-nucleotidase from chicken liver. Purification and some properties. 94 52

Administration to rats of D-galactosamine (400 mg/kg) produces liver cell death that develops during the first 24 hours. Plasma membranes isolated within the first few hours from these animals show a 40% reduction in 5'-nucleotidase activity and a two-fold increase in maximum negative ellipticity determined by circular dichroism. Simultaneous administration of uridine prevents liver cell death and these early alterations in the plasma membranes. Uridine also prevents cell death if administered for up to 3 hours after galactosamine. The 5'nucleotidase activity reduced when uridine is administered for up to 2-1/2 hours after galactosamine. Changes in the liver calcium ion concentration accompany these plasma membrane alterations. Uridine will prevent and reverse the changes in calcium content in parallel to its ability to reverse the membrane alterations. The significance of these findings with respect to the mechanism of galactosamine-induced liver cell death is discussed.
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PMID:Early, reversible plasma membrane injury in galactosamine-induced liver cell death. 113 5

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.
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PMID:5'-nucleotidase: an ecto-enzyme of frog skeletal muscle. 114 56

5'-nucleotidase (EC 3.1.3.5), an important enzyme in the metabolism of nucleotides, is generally accepted as a plasma membrane marker. The enzyme selectively splits phosphoric acid from 5' mononucleotides. Several methods are available for the histochemical localization of enzymes (antigenic properties of the enzyme protein, enzyme properties and activity and labelled specific inhibitors). Only the method based on enzyme properties has been used up to now in the case of 5'-nucleotidase. Free phosphoric acid liberated during the dephosphorylation of substrates such as AMP or IMP is rendered visible at the sites of 5' nucleotidase activity in the tissue by precipitation as lead or calcium phosphate. An improvement in the light microscopic technique is achieved by the use of freezedried tissue embedded in glycol methacrylate, whereby the histochemical reaction can be performed on semi-thin sections. Since lead phosphate is electron dense, these precipitates can easily be detected in the electron microscope too. Wide species and organ differences are found with respect to the distribution of 5'-nucleotidase activity. The well-known localization of the enzyme on the outer cell surface according to biochemical studies is confirmed by electron microscopic findings. A purely catabolic function of 5'-nucleotidase, as propounded in the literature, seems dubious since high 5'-nucleotidase activity was demonstrated in rapidly proliferating tissue too.
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PMID:[Light and electron microscopic localization of enzymes: 5'-nucleotidase (author's transl)]. 122 68

The present state of investigations on molecular and cellular mechanisms of cardioprotective effects of phosphocreatine (PCr) is reviewed. The protective effect of PCr is manifested as significant improvement of heart contractile function recovery, lowering of diastolic pressure elevation and myocardial enzymes release during postischemic reperfusion as well as better preservation of high energy phosphates in comparison with control. Data from multidisciplinary studies using physico-chemical, physiological, pharmacological etc. approaches suggest that one of the key mechanisms of PCr action is its interaction with the sarcolemmal membrane. The authors own data obtained with the use of spin-labeled ESR-probe incorporated into the isolated sarcolemmal vesicles provide direct evidence in favor of the ordering effect of PCr sarcolemmal phospholipid packing with essential involvement of Ca2+ ions. PCr transform membrane phospholipids into more structured gel-like state. The results of biomedical studies suggest that the mechanism of this protective action is complex and includes at least four components: 1) inhibition of lysophosphoglyceride accumulation in the ischemic myocardium and preservation of cardiac cell sarcolemma structure via zwitterionic interaction with PCr molecules; ii) extracellular action consisting in inhibition of platelet aggregation via ADP removal in the extracellular creatine kinase reaction and increasing plasticity of red blood cells; iii) PCr penetration into cells maintenance of high local ATP levels is possible; iiii) inhibition of adenine nucleotide degradation at the step of 5'-nucleotidase reaction in cardiac cell sarcolemma.
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PMID:[Molecular and cellular aspects of the cardioprotective mechanism of phosphocreatine]. 129 51

The regulation by ATP of Cl- secretion in T84 cells grown on filters was investigated by measuring short-circuit current (Isc = net Cl- secretion). ATP (greater than or equal to 10 microM) added to the basolateral side markedly stimulated Isc both in the presence and absence of forskolin-activated Isc. Fluorescence microscopy of cells loaded with the Ca2+ indicator fura-2 showed that ATP stimulated a transient increase in intracellular free Ca2+ concentration [Ca2+]i. The augmentation of forskolin-stimulated Isc by ATP was at least partly caused by mobilization of Ca2+ from an internal store because prior depletion of the store using ionomycin prevented the response. The activity sequence for stimulation of Isc in the presence of forskolin was adenosine 5'-O-(3-thiotriphosphate) = 5'-adenylylimidodiphosphate (AMP-PNP) greater than ATP greater than ADP greater than AMP, suggesting the presence of a P2 purinergic receptor. Neither beta, gamma-methyleneadenosine 5'-triphosphate nor alpha, beta-methyleneadenosine 5'-triphosphate increased the Isc. Stimulation of Isc by ATP in the absence of forskolin was at least partly due to the breakdown of ATP to AMP and adenosine, which act at P1 receptors to stimulate Isc, since 1) inhibition of the ecto-phosphohydrolase 5'-nucleotidase by alpha, beta-methylene-ADP partially inhibited stimulation of Isc by ATP, 2) the adenosine receptor antagonists caffeine and 8-phenyltheophylline markedly inhibited the ATP-stimulated Isc, and 3) AMP-PNP, a weakly hydrolyzable analogue of ATP, caused a much smaller increase in Isc compared with ATP. Adenosine had no effect on [Ca2+]i.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Purinergic receptor activation of Cl- secretion in T84 cells. 131 Feb 17

Mesangial cells possess a variety of receptors for hormones and autacoids. They are also equipped with ectoenzymes whose function may be to control the availability of autacoids and hormones at their receptor sites. Several examples are considered. Receptors for angiotensin II (AII) are present both on murine and human mesangial cells. One single group of receptors has been demonstrated in each of these preparations. Mesangial cell AII receptors are linked to phospholipase C via a G protein. They belong to the AT1 subtype because (125I)AII is displaced from its binding sites preferentially by AT1 antagonists such as DUP 753 and EXP 3,174, whereas AT2 antagonists are much less potent. AT1 antagonists suppress the biological effects of AII in mesangial cells, including the stimulation of intracellular calcium concentration and the increase of prostaglandin synthesis and of (3H)leucine incorporation. Mesangial cells also have receptors for atrial natriuretic factor, but the distribution between B receptors with guanylate cyclase activity and clearance (C) receptors varies with the species. Both types are present in murine mesangial cells, whereas only C receptors are found in human mesangial cells. In contrast, human epithelial cells possess both B and C receptors. Ecto-5'-nucleotidase activity results in the production of adenosine, which acts on mesangial cells through A1 and A2 receptors. This enzyme is markedly induced in rat mesangial cells by interleukin-1, whose effect is mediated in part by prostaglandin E2 and cAMP. Various other cAMP-stimulating agents also induce 5'-nucleotidase expression in rat mesangial cells. Ectopeptidases are present in all glomerular cell types but essentially in epithelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cell surface receptors and ectoenzymes in mesangial cells. 131 10

The binding of [125I]endothelin-1 (125I-ET-1) to membranes from whole rat brain, from individual brain regions, and derived from subcellular fractionation of whole rat brain was investigated. 125I-ET-1 binding to whole rat brain membranes was rapid, concentration-dependent, saturable, and characterized as irreversible because it was not displaced by unlabeled endothelin-1 (ET-1) and different concentrations of ligand produced, with time, a similar magnitude of binding. The maximum binding site capacity and second-order forward rate association constant of binding were 1,946 +/- 147 fm/mg protein and 5.53 +/- 1.72 x 10(6) M-1 s-1. Removal of either extramembranal calcium or membrane-bound calcium and calcium binding proteins did not affect the binding of 125I-ET-1 to whole rat brain membranes. The brain stem and cerebellum contained the highest levels of 125I-ET-1 binding sites, whereas the cerebral cortex, striatum, and hippocampus contained binding site levels three- to fourfold less. Subcellular fractionation of whole rat brain and subsequent analyses of the distribution of 125I-ET-1 binding demonstrated a twofold enrichment of binding sites in the synaptosomal fraction compared to the homogenate. The myelin fraction contained a similar density of binding sites compared to the homogenate, while the mitochondrial and microsomal fractions contained considerably less binding sites. The ribosomal fraction did not contain any 125I-ET-1 binding sites. The subcellular distribution of 125I-ET-1 binding sites did not correlate with the distribution of 5'-nucleotidase, cytochrome-C oxidase, phosphodiesterase, and alkaline phosphatase. Depletion of extracellular calcium increased 125I-ET-1 binding in the synaptosomal fraction but not in the myelin and mitochondrial fractions.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Regional and subcellular distribution of [125I]endothelin binding sites in rat brain. 131 99

Studies have demonstrated that augmenting the omega 6 polyunsaturated-fatty-acid (PUFA) content of N1E-115 neuroblastoma cells by media supplementation with linoleic acid results in greater than or equal to 2-fold increases in basal levels of intracellular cyclic AMP (cAMP). Data suggested some involvement of increased production of adenosine from endogenous metabolites; however, increases in adenosine were not related to increased activity of 5'-nucleotidase or decreased uptake of extracellular adenosine. PUFA-dependent elevations in basal cAMP were evident within 1 min of exposure to a phosphodiesterase inhibitor; this phenomenon did not appear to be due to PUFA-dependent changes in Ca2+ uptake or to increases in sensitivity of adenylate cyclase to Ca2+. Forskolin-stimulated cAMP formation was 3-fold higher in PUFA-enriched cells than in control cells, which suggested a direct effect on the functioning of the catalytic unit. Linoleic acid supplementation resulted in a 2-fold increase in the maximum amounts of cAMP produced in response to the stable adenosine analogue, 5'-N'ethylcarboxy-amidoadenosine (NECA). The altered stimulatory response did not involve eicosanoid formation, but may have been related to an increase in the number of stimulatory adenosine receptors, as judged by binding of [3H]NECA. These studies indicate that membrane PUFA modulate adenosine-related functions in neuroblastoma cells, and suggest that a complex series of mechanisms is involved in this regulation.
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PMID:Non-eicosanoid functions of essential fatty acids: regulation of adenosine-related functions in cultured neuroblastoma cells. 132 28


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