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

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

In the present paper the mechanism of the adenosine formation by a mixture of nerve ending and transmitter granula fractions was invesitgated. The adenosine formation in vivo is only possible via the whole degradation chain ATP - ADP - AMP - adenosine. The enzymes involved are ATPases, adenylate kinase and 5'-nucleotidase. The ATPase and adenylate kinase effectors Ca++ and Mg++ can be regarded as trigger ions switching on and off the degradation chain. The adenylate kinase represents a key enzyme within the whole chain. In the ion-activated state a non-inhibited adenosine formation was observed, when the initial ATP concentration amounted to less than 0,1 muMol per mg synaptosomal membrane protein. Under these conditions the whole chain velocity is mainly dependent on the 5'-nucleotidase concentration, because ATPases and adenylate kinase remove the nucleotidase inhibitors ATP and ADP spontanously. The conditions for the optimal velocity of the adenosine formation at the synaptic membrane in vivo in all probability are present. A hypothesis for the mechanism of the synaptic adenosine formation in vivo was developed. The importance of this process in respect to the synaptic transmission was discussed.
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PMID:[Mechanism of synaptosomal degradation of ATP in connection with involvement of adenosine in the transmission process]. 12 26

A Golgi apparatus-rich fraction and a plasma membrane-rich fraction were isolated from a common homogenate of rat liver. Their respective buovant densities, appearances in the electron microscope and 5'-nucleotidase and UDP-galactose ovalbumin galactosyltransferase activities were in accord with published data on separately isolated Golgi apparatus-rich and plasma membrane-rich fractions. Contamination by endoplasmic reticulum and mitochondria was low. Gel electrophoresis of the membrane proteins of the Golgi apparatus-rich and plasma membrane-rich fractions (separately and mixed) showed a close similarity. After Neville's demonstration that electrophoretic patterns of membrane protein subunits from different subcellular fractions are easily distinguishable, the present work demonstrates an unusually close relationship between the Golgi apparatus membrane and the cell membrane. It is possible that membrane similarity may be mediated by the transfer of membrane-bound vesicles from the Golgi apparatus to the cell membrane.
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PMID:Similarities of the Golgi apparatus membrane and the plasma membrane in rat liver cells. 17 74

1. Enzymes, proteins, glycoproteins and lipids of rodent bile were compared with those of a plasma-membrane subfraction originating from the hepatocyte bile-canalicular membrane. 2. Three bile-canalicular glycoprotein enzyme activities were detected in bile. Comparison of the pH optimum and immunoinhibition properties of membrane and bile 5'-nucleotidase activity indicated that they were the same enzyme. Correspondence between membrane and bile alkaline phosphodiesterases also suggested that they were the same enzymes. Activities of Mg2+-stimulated adenosine triphosphatase, a lipid-dependent intrinsic membrane protein, and galactosyltransferase, a Golgi membrane marker, were not detected in bile. 3. Rodent bile contained 15 polypeptide bands that differed radically from those of bile-canalicular membranes. Bands that may correspond in molecular weight to liver plasma-membrane glycoproteins were present at low staining intensities in bile. A major protein of apparent molecular weight 49 500 was present, and albumin was detected by immunodiffusion. 4. The lipid composition of bile and bile-canalicular membrane also differed. Phosphatidylcholine accounted for 82% of rat bile phospholipids, and only trace amounts of phosphatidylinositol, phosphatidylserine and sphingomyelin were present. 5. The results indicate that in healthy animals, the bile-canalicular membrane is refractory to the action of bile acids during the secretory process. The presence of only small amounts of bile-canalicular membrane components, especially glycoprotein enzymes located at the outer face of the membrane, suggests that these are released from the membrane by bile acids after secretion of bile into the canalicular spaces.
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PMID:Role of membranes in bile formation. Comparison of the composition of bile and a liver bile-canalicular plasma-membrane subfraction. 18 22

The purpose of this experimental investigation was to provide a purified plasma membrane fraction containing a highly hormone-responsive adenylate cyclase system. Bovine adrenal cortex was homogenised and a washed pellet (450 000 X g - min) was fractionated by zonal centrifugation in a sucrose and dextran gradient. Adenylate cyclase activity was purified up to 60-fold to a specific activity of 55, 340 and 210 pmol of adenosine 3':5'-monophosphate (cyclic AMP) produced/minute per mg of protein at 38 degrees C for the basal, adrenocorticotrophin and fluoride-activated states, respectively. The time course of the adenylate cyclase activity is linear. The concentration necessary for half-maximal stimulation by adrenocorticotrophin-(1-24)-tetracosipeptide is 0.5 muM. The high hormone-responsiveness of the membrane preparation allows one to demonstrate activation of adenylate cyclase by very weakly agonistic adrenocorticotrophin fragments. The F- activated state can be detergent-dispersed by Lubrol and shows a Km (ATP) different from that of either the basal or adrenocorticotrophin-stimulated state. Other marked enzymes such as 5'-nucleotidase, glucose-6-phosphatase and cytochrome oxidase were followed during purification. The plasma membrane fraction shows rather homogeneous, relatively large vesicles (mean diameter 0.5 mum). It contains high-affinity binding sites for angiotensin II (about 2 pmol per mg protein) with an apparent association constant of 2 X 10(7) (1/mol) at 12 degrees C. The yield, 20 mg of membrane protein per preparation, may make it a tool in either affinity-labelling studies with the peptide hormones mentioned or the starting point for solubilisation and purification of adenylate cyclase.
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PMID:Purification of bovine adrenal-cortex plasma-membrane vesicles containing a highly corticotropin-sensitive adenylate-cyclase system and angiotensin-II-binding sites. 19 4

The effects of amphotericin B drug containing sodium deoxycholate (DOC) and those of DOC and nistatin on the activities of Na+, K+-ATPase and 5'-nucleotidase of canine kidney plasma membranes were studied. It was found that the activities of Na+, K+-ATPase and 5'-nucleotidase were markedly inhibited only after intravenous injection of amphotericin B, whereas the other agents tested caused no changes in the enzyme activities. Similar results were obtained in vitro. In the presence of amphotericin B the activity of Na+, K+-ATPase was noticeably inhibited already at the antibiotic concentration of 0,1 mkg per mg of membrane protein. It was found that the injection of amphotericin B, DOC and nistatin did not qualitatively or quantitatively affect the phospholipid composition of the plasma membranes. This is indicative of the lack of correlation between the enzyme activities and changes in the phospholipid composition of the plasma membranes under effects of amphotericin B. The pyrimidine derivative--amygluracyl--markedly removes the inhibiting effect of amphotericin B on the enzyme activity of plasma membranes.
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PMID:[Activities of enzymes from canine kidney plasma membranes under effects of polyene antibiotics in vivo and in vitro]. 21 53

Ovine prolactin, labelled with 125I by either lactoperoxidase or a mild chloramine T method, bound to receptors from the pigeon crop sac mucosa cells of prolactin-injected pigeons. Binding was demonstrated in a crude homogenate of mucosal cells removed from the crop by scraping and in a subcellular fraction in which 5'-nucleotidase activity was enhanced two- to threefold. The binding was specific, dependent on time, temperature and the concentration of receptors and had a dissociation constant of 7 X 10(-10) mol/l. The binding capacity of the crop tissue was 71 fmol/mg membrane protein. Nine purified preparations of prolactin from four species were assayed by local pigeon crop sac bioassay and by radioreceptor assay. The two methods were highly correlated (r = 0.934). The regression equation was radioreceptor assay = 1.22 bioassay--0.18 indicating a 1 : 1 correspondence between the two methods for prolactin purified from sheep, rat, horse and pig anterior pituitary glands.
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PMID:A pigeon crop sac radioreceptor assay for prolactin. 21 43

A detailed binding study of 125I-labeled diphtheria toxin to isolated cell surface membrane-enriched fractions is reported. The study was undertaken to determine if toxin-resistant species exhibit a defet in either the binding step or the transport step of the intoxication process. Surface membrane fractions were obtained from liver and mammary glands of toxin-sensitive species, rabbit and giunea pig, and toxin-resistant species, rat mouse. All membrane fractions exhibited reversible binding of 125I-toxin which was competitively inhibited by unlabeled toxin. Toxin receptors from liver co-purified with plasma membranes and the plasma membrane marker 5'-nucleotidase. One-half saturation of all receptors occurred between 5 x 10(-8) and 1.8 x 10(-7) M. Scatchard plots were nonlinear and concave upwards. Total receptor sites ranged from 3.4 to 16 pmol/mg of membrane protein, tissue differences being more pronounced than difference between sensitive and nonsensitive species. Over 95% of the toxin specific binding was inhibited by removal of divalent cation from the medium or by the inclusion of 1 mM ATP, procedures which have been shown to protect sensitive cells from intoxication by diphtheria toxin. We conclude that the rat and mouse have surface membrane receptors for diphtheria toxin and that the toxin insensitivity of these species results from a defect in or a lack of the transport process.
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PMID:Demonstration of diphtheria toxin receptors on surface membranes from both toxin-sensitive and toxin-resistant species. 69 Jan 29

Plasma membrane proteins and glycoproteins have been isolated from Chinese hamster cells of the spontaneously transformed DC-3F parental cell line and the DC-3F/AD X line with a high level of acquired resistance to actinomycin D. Plasma membrane preparations from both cell lines band at 1.16 g/ml after isopycnic centrifugation. We present evidence to indicate differences in the leucylpeptide backbones of the antibiotic-sensitive cells and the drug-resistant DC-3F/AD X cells. In addition, there are differences in the plasma membrane glycopeptides of the two cell lines as revealed by sodium dodecyl gel electrophoresis. Drug-resistant cells synthesize a surface glycopeptide which is much larger than the major one present on the drug-sensitive cells. Both of these cell lines are devoid of 5'-nucleotidase and alkaline phosphatase activities. The role of plasma membrane protein differences in drug-resistant cells is discussed.
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PMID:Plasma membrane proteins and glycoproteins from Chinese hamster cells sensitive and resistant to actinomycin D. 74 79

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

The human neutrophil neutral peptide-generating protease was associated with the plasma membrane marker 5'-nucleotidase on sucrose density gradient centrifugation of sonicates of granule-free fractions following homogenization and velocity sedimentation. The two activities were also associated on sucrose density gradient fractionation of plasma membranes obtained by hypotonic lysis in EDTA containing buffers, a technique which minimizes aggregation. Treatment of fractions containing these enzymatic activities with 1-0 M NaCl separated the neutral peptide-generating proteasein to the eluate while leaving the 5'-nucleotidase in the pellet. Gel filtration of the solubilized neutral peptide-generating protease through Sephadex G-100 in 1-0 M NaCl demonstrated that the protease had an approximate mol. wt of 20,000 while filtration in physiological salt concentrations yielded activity only in the excluded volume. In both cases, there was complete recovery of neutral peptide-generating activity suggesting that the filtration characteristics of the protease were determined by the salt concentration. The solubilized purified protease, the whole cell sonicates, and the intact cells interacted with heat-inactivated plasma to yield the same product, a neutral peptide with a 1000 molecular weight and an isoelectric point of 7-2-7-6. The neutral peptide-generating protease in each instance was inhibited in dose-response fashion by alpha-1-antitrypsin, LBTI, and DFP. Only 30-60% of the protease sites were functional on intact cells as revealed by substrate cleavage or were available to inhibitors. The neutrophil protease which generates neutral peptide is an extrinsic plasma membrane protein with an approximate mol. wt of 20,000 which functions as an ectoenzyme.
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PMID:A neutrophil-dependent pathway for the generation of a neutral peptide mediator. II. Subcellular localization of the neutrophil protease. 87 75


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