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)

The presented paper describes the role of enzyme histochemistry in cell biological investigations. In the first chapter a general discussion has been given about enzyme histochemistry as a connecting link between biochemistry and morphology. The methods available for determination of enzymes in a particular cell or cell compartment have been reviewed. In this respect the characteristics of enzyme histochemistry have been discussed. Furthermore, attention has been paid to the possibilities and limitations of enzyme histochemistry. In chapter two a comparison has been made between histochemically judged and biochemically determined enzyme activities. Some fundamental differences between the biochemical and the histochemical approach in cell biological investigations are dealt with. To correlate histochemically and biochemically determined enzyme activities, a description has been given of the application of histochemical methods on isolated fractions and sucrose-ficoll gradients of these fractions. Several experimental results are described concerning the question whether a relation exists between histochemically and biochemically determined activities of respectively alkaline phosphatase, glucose-6-phosphatase, 5'-nucleotidase and 3ss-hydroxysteroid dehydrogenase. From these results the conclusion could be drawn that in general a good correlation exists between histochemically judged activity per volume (area X thickness) and biochemically determined activity per gram tissue. In chapter three the role of enzymes as markers of cellular particles and as parameters of metabolic pathways is described. Histochemical methods are available for most marker enzymes. Only activities of key enzymes can be regarded as parameters of metabolic pathways. The distribution in sucrose-ficoll gradients of enzymes, regarded as markers of mitochondria, lysosomes, endoplasmic reticulum and plasma membranes has been given. The changes occur ing under different experimental conditions for a number of marker enzymes in rat liver are described. Attention has been given to the contibution of enzyme histochemistry in the study of the heterogeneity of mitochondria, the dual localization of some (lysosomal) enzymes, the complexity of the microsomal fraction, the function of the Golgi apparatus and the heterogeneity and function of plasma membranes. Based on these results and on literature findings the possible role of some marker enzymes in cell metabolism has been discussed. In chapter four problems coherent with species and sex differences in enzyme activities are described. The interpretation of histochemical and biochemical results in view of these differences is discussed. Enzymes characteristic for a given cell type -3ss-hydroxysteroid dehydrogenase in steroid producing cells, ATP-ase in liver plasma membrane surrounding the bile canaliculi - do show less variations between species and sexes than enzymes not directly involved in specialized functions...
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PMID:Enzyme histochemistry as a link between biochemistry and morphology. 18 46

Activities of a broad spectrum of enzymes were studied histochemically in renal adenocarcinomas induced in young male F344 rats by chronic dietary administration of the carcinogen N(4'-fluoro-4-biphenylyl)acetamide. Enzymes included were: dehydrogenases of glucose-6-phosphate, lactate, succinate, malate, and alpha-glycerophosphate; peroxidase (catalase); glucose-6-phosphatase; alkaline and acid phosphatase; Mg2+ ATPase; 5'-nucleotidase; and aminopeptidase. Levels of enzyme activity were estimated visually and scored from 0 (not detectable) to a maximum of 5 (intense). Comparison of estimated activity for each enzyme was made between small neoplastic nodules (stage III tumors) and large adenocarcinomas (stage IV tumors) and between tumors and portions of normal proximal tubules in parenchyma of kidneys from untreated control rats. The results, which revealed nearly identical levels of activity for most enzymes in both stages III and IV tumors, suggested similar metabolic and biologic behavior of these lesions. However, when data for tumors were compared with data for normal proximal tubules, striking differences were observed consistent with: 1) a marked shift of energy metabolism from oxidative to glycolytic production of ATP, with a corresponding reduction in mitochondrial respiration; and 2) simplification of plasma membrane specializations that were possibly associated with a reduction or loss of transport function. These findings were compared with other histochemical, biochemical, and ultrastructural studies of renal adenocarcinomas in rats and man.
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PMID:Adenocarcinoma of the kidney. II. Enzyme histochemistry of renal adenocarcinomas induced in rats by N-(4'-fluoro-4-biphenylyl)acetamide. 18 77

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

A comparative study of glucose-6-phosphatase, alcaline RNase, ATPase, inosine diphosphatase and 5'-nucleotidase activities in isolated rat liver and hepatoma-27 nuclei and nuclear envelopes was performed. The tumor nuclear membranes were shown to be free from G-6-Pase activity in contrast to the liver nuclear membranes. The nuclear RNase activity was strongly inhibited in the hepatoma and could be unmasked in the presence of 3-10(-4) M pCMB. Hepatoma nuclear and nuclear envelopes ATP-ase activity was found to be moderately decreased as compared to those of the normal tissue. The values of inosine diphosphatase activity in hepatoma were similar to those in liver. The role of the nuclear envelope in nuclear-cytoplasmic interactions as well as nuclear location of G-6-Pase are discussed.
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PMID:[Various enzymes of isolated nuclear membranes and cell nuclei of the liver and hepatoma 27 of rats]. 19 29

From a homogenate of rabbit colon muscle subcellular fractions were isolated by differential centrifugation. The crude microsomal fraction could be separated into subfractions, a fraction of vesicular microsomes at 35% sucrose, a fraction containing sarcolemma, mitochondrial fragments and microsomal vesicles at 35--45% sucrose and a small protein fraction at 45--55% sucrose. Their biochemical properties and their morphological characterization were investigated. The cholesterol and the phospholipid content was equally distributed between the microsomal fractions 35% and 35--45% while the RNA was localized to the mitochondria and the microsomal fraction 35%. The enzyme cytochrome c oxidase was found to be concentrated in the mitochondria while a high contamination was found in the microsomal fractions 35--45%. The NADH-oxidase activity was highest in the 35% fraction and the 5'-nucleotidase activity in the 40,000 X g supernatant. The microsomal subfractions contained the enzymes ATPase, adenylate cyclase and phosphodiesterase. In the 35% fraction Ca stimulated the hydrolysis of ATP. The binding of [3H]-ouabain and the incorporation of [3H]-leucine was most pronounced in the 35% fraction. In a K+-free Krebs Ringer medium the binding of the glucoside was stimulated in all the fractions. From these results we concluded that the fraction 35% sucrose may be mainly derived from the endoplasmic reticulum and the plasma membrane while the 35--45% originates from the plasma membrane, mitochondria and to a lesser extent the endoplasmic reticulum.
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PMID:Biochemical and morphological characterization of subcellular fractions isolated from rabbit colon muscle. 20 90

The properties of a number of enzyme activities of the superovulated rat ovary have been studied to establish optimal assay conditions and specific assay procedures for each activity. The activities were chosen on the basis of their extensive use in other tissues of the rat as marker enzymes for the major cell organelles. Homogenates of superovulated rat ovaries were subjected to fractionation by differential rate centrifugation, and sedimentation profiles were constructed for each marker enzyme activity. The various subcellular fractions were also monitored by electron microscopy. The enrichment of fractions with particular organelles by electron microscopy, and enrichment of the appropriate organelle marker enzyme activities correlated well. Sedimentation profiles of a number of plasma membrane marker enzymes demonstrated a marked discrepancy between hCG-binding activity, and 5'-nucleotidase-, alkaline phosphatase-, and Mg2+-dependent ATP-ase on the one hand, and basal, hCG-stimulated, and fluoride-stimulated adenylate cyclase activities on the other hand. Fractions enriched in hCG-binding and adenylate cyclase activities were subjected to further fractionation on discontinuous sucrose density gradients. The distributions of the various plasma membrane markers again indicated a partial dissociations between hCG-binding and adenylate cyclase activities of luteinized rat ovaries, suggesting the existence of two distinct major plasma membrane populations, with different buoyant densities, marker enzyme profiles and adenylate cyclase and hormone-binding levels.
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PMID:Interactions of gonadotropins with corpus luteum membranes. I. Properties and distributions of some marker enzyme activities after subcellular fractionation of the superovulated rat ovary. 21 56

1. Isolated nerve terminals (T-sacs and synaptosomes) prepared from the purely cholinergic Torpedo electric organ have been studied for their ability to incorporate and metabolise [2-3H] adenosine and to degrade 5'-AMP to adenosine. 2. A temperature-dependent, saturable uptake system for adenosine was found with kinetic properties similar to nucleoside transport systems in other cells. The uptake system in Torpedo nerve terminals was inhibited by 2'-deoxyadenosine, a known inhibitor of adenosine transport. 3. Intraterminal adenosine is rapidly metabolised to a number of products including AMP, ADP and ATP. 4. Isolated nerve terminals contain considerable 5'-nucleotidase activity, most of which resides on the outer face of the external membrane. The Km of the enzyme is congruent to 5 micron and it is inhibited by a phosphonate analogue of ADP, alpha-beta-methylene-ADP. It is suggested that this 5'-nucleotidase plays an important role in the production of adenosine from a nucleotide pool in the synaptic cleft.
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PMID:Adenine nucleotides in cholinergic transmission: presynaptic aspects. 21 98

The activities of dTMP kinase (ATP-deoxythymidine monophosphate phosphotransferase, EC 2.7.4.9), 5'-nucleotidase (5'-ribonucleoside phosphohydrolase, EC 3.1.3.5), adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4), AMP deaminase (AMP aminohydrolase, EC 3.5.3.6) and ATP-(Mg2+)-ase (ATP phosphohydrolase, EC 3.6.1.3) were assayed in mitochondria of normal and regenerating rat liver. In regenerating mitochondria, the dTMP kinase activity increased 20 times, 5'-nucleotidase (5'Nase) activity for dTMP diminished by 65% and its activity for other nucleoside monophosphates did not change; adenosine deaminase activity for adenosine (AR) increased by 40%, but for deoxyadenosine (AdR) decreased by 70%. AMP deaminase and ATP-(Mg2+)-ase activities behaved similarly in mitochondria from regenerating liver, decreasing by 70 and 64% respectively. The changes of the amount of dTMP in mitochondria depend on enzyme activities which regulate the AdR concentration.
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PMID:Relationship between 5'-nucleotidase, adenosine deaminase, AMP deaminase, ATP-(Mg2+)-ase activities and dTMP kinase activity in rat liver mitochondria. 22 41

Radioactively labelled adenosine and adenine were rapidly taken up by isolated rat fat cells, and incorporated into nucleotides, of which ATP dominated. The overall process had an apparent Km of 1--5 micrometers. During incubation, especially in the presence of lipolytic agents, there was a reduction in labelled ATP with a compensatory increase in ADP, AMP, cAMP and nucleosides. The build-up of adenosine during incubation was inhibited by theophylline, which inhibits 5'-nucleotidase. Radioactivity released from perifused fat cells consisted mainly of nucleoside material, of which adenosine predominated. Lipolytic stimulation caused no significant increase in nucleoside outflow from perifused cells, whereas oxygenation was capable of reducing this outflow. It is concluded that adenosine is formed by fat cells as a consequence of ATP breakdown. Stimulation of lipolysis during activation of the sympathetic nerves leads to reversible ATP breakdown and adenosine release. Adenosine might therefore act as a modulator of lipolysis in vivo under these conditions, even though it does not serve as a feed back regulator in the proper sense.
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PMID:Uptake and release of adenosine in isolated rat fat cells. 22 Aug 45

Deoxyadenosine metabolism was investigated in cultured human cells to elucidate the biochemical basis for the sensitivity of T lymphoblasts and the resistance of B lymphoblasts to deoxyadenosine toxicity. T lymphoblasts have a 20-to 45-fold greater capacity to synthesize deoxyadenosine nucleotides than B lymphoblasts at deoxyadenosine concentrations of 50--300 micron. During the synthesis of dATP, T lymphoblasts accumulate large quantities of dADP, whereas B lymphoblasts do not accumulate dADP. Enzymes affecting deoxyadenosine nucleotide synthesis were assayed in these cells. No substantial differences were evident in activities of deoxyadenosine kinase (ATP: deoxyadenosine 5'-phosphotransferase, EC 2.7.1.76) or deoxyadenylate kinase [ATP:(d)AMP phosphotransferase, EC 2.7.4.11]. The activity of 5'-nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) was increased 44-fold for AMP and 7-fold for dAMP in B lymphoblasts. A model for the regulation of deoxyadenosine nucleotide synthesis by 5'-nucleotidase activity is proposed on the basis of the observations.
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PMID:Biochemical basis for differential deoxyadenosine toxicity to T and B lymphoblasts: role for 5'-nucleotidase. 22 24


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