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

The purpose of this study was to try to differentiate histochemically between the various enzymes which may catalyze the hydrolysis of ATP in developing rat dental tissues. Freeze cut and freeze dried sections of molar and incisor teeth were incubated in lead capture-based media at pH 5.0, 7.2 or 9.4 with one of the following substrates: beta-glycerophosphate, AMP, ADP, ATP, AMP-PNP and tetrasodium pyrophosphate. To establish the enzymatic nature of the hydrolysis parallel sections were incubated after prior fixation in either formaldehyde or glutaraldehyde. By comparing the enzymatic stainings obtained with the various substrates and at the different pH:s, it was concluded that ATP can be visibly hydrolyzed in rat dental tissues by alkaline phosphatase (stratum intermedium, apical part of maturation ameloblasts, basal part of all ameloblasts, odontoblasts and subodontoblastic layer), specific ATPase (apical and basal parts of secretory ameloblasts) and ATP pyrophosphatase and/or adenylate cyclase (stratum intermedium, odontoblasts). Acid phosphatase, specific ADPase, 5'-nucleotidase, inorganic pyrophosphatase, 3':5'-cyclic-AMP-phosphodiesterase and adenylate kinase on the other hand, seem not to be engaged in the ATP hydrolysis to such a degree as to complicate the interpretation of the histochemical staining. The alkaline phosphatase part of the ATP hydrolysis appeared to be rather insensitive to aldehyde fixation, while the hydrolysis effected by specific ATPase and ATP pyrophosphatase and/or adenylate cyclase was extinguished after fixation with formaldehyde for 4 h or glutaraldehyde for 10 min.
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PMID:Adenosine triphosphate hydrolysis in rat dental tissues. A histochemical study to differentiate the enzymes involved. 18 60

Mitochondrial and microsomal fractions were isolated from guinea pig myocardium by differential pelleting. The mitochondrial fraction was subjected to analytical subfractionation by sucrose density gradient centrifugation and the gradient fractions assayed for marker enzymes for the various mitochondrial compartments, viz outer membrane (monoamine oxidase), intermembranous space (adenylate kinase), inner membrane (Mg2+-dependent ATPase and cytochrome c oxidase) and mitochondrial matrix (malate dehydrogenase), and for creatine kinase. Both creatine kinase and adenylate kinase were released by suspending the mitochondria in 50 mmol . litre-1 sodium phosphate buffer. Sonication or disruption with the detergent, digitonin released the adenylate kinase but the creatine kinase remained associated with the inner membranes. Subsequent salt treatment desorbed the creatine kinase from these membranes. It is concluded that creatine kinase is located to the outer aspect of the inner mitochondrial membrane. Analytical subfractionation of the microsomal fraction clearly resolved markers for the sarcolemma (5'-nucleotidase), outer mitochondrial membrane (monoamine oxidase) and endoplasmic reticulum (neutral alpha-glucosidase and RNA). Creatine kinase was localised in the endoplasmic reticulum particularly the smooth membranes.
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PMID:Sub-mitochondrial and sub-microsomal distribution of creatine kinase in guinea pig myocardium. 51 58

Enzymopathies are described concerning the enzymes of the oxidative pentose phosphate pathway including the glutathion system, of the majority of glycolytic enzymes as well as of the ATPase, adenylate kinase and pyrimidine-5'-nucleotidase. The distribution and the frequency of the enzymopathies differ strongly in the various regions of the world. Glucose-6-phosphate dehydrogenase and pyruvate kinase show the highest frequency. The detected polymorphism of the pathological enzyme variants is one of the reasons for the fact that no correlation between the decrease of the catalytic activity and the severity of the anaemias has been found. For the identification of risk-groups more precise methods are necessary. Till now the detailed relationships between enzymopathy and non-spherocytic haemolytic anaemias are not clarified. Furthermore the molecular mechanism of the instability of pathological enzyme variants is not yet clear.
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PMID:[Enzyme deficient non-spherocytic hemolytic anemias]. 67 10

It was found that mitochondria from human placenta exhibited an ADPase activity with the following characteristics. The enzyme responsible for this activity was associated with the inner mitochondrial membrane. It was not released by treatment of the submitochondrial particles with solutions of high ionic strength. Maximal ADP hydrolysis was reached at pH 8. Specific inhibitors for alkaline phosphatase (L-phenylalanine), myokinase (P1,P5-di(adenosine-5')pentaphosphate), or 5'-nucleotidase (concanavalin A) did not decrease ADP hydrolysis. ATP synthesis from ADP by myokinase was about 13 nmol/mg/min, whereas ADP hydrolysis reached values around 500 to 550 nmol/mg/min, indicating that a myokinase-H+ATPase combination could not account for the observed rates of ADP hydrolysis. The activity was stimulated by Mg2+, but high concentrations of this cation produced inhibition. High ADP concentrations did not inhibit ADPase activity. Kinetic measurements of the activity in the submitochondrial particles showed that the true substrate was ADP-Mg. The kinetic studies showed V(app) values of 476 and 270 nmol/mg/min, and Kmapp values of 416 and 8.7 microM.
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PMID:Subcellular localization and properties of adenosine diphosphatase in human placenta. 147 Jun 6

Pyrimidine 5'-nucleotidase (P5'N) partial deficiency has been described in several hematological disorders and also in the beta-thalassemic trait. To check if the P5'N deficiency in thalassemia was acquired we used thalassemic red cells (from either homo- or heterozygous subjects), whose P5'N activity was lower than in control cells. After separation on a density gradient, activity in lighter cells was similar to controls and less than 50% in denser cells. The most probable mechanism for this faster inactivation involves enzyme -SH groups modification by oxidation and reaction with monofunctional aldehydes produced by membrane lipid peroxidation. In vitro challenge of thiol enzymes as pyruvate kinase (PK), adenylate kinase (AK) and P5'N with increasing concentrations of GSSG, hexanal (HEX) and 4-hydroxynonenal (HNE), showed that HNE is the most powerful among the enzyme inhibitors tested and that P5'N activity is a more sensitive index of -SH groups damage, when compared to PK and AK.
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PMID:Pyrimidine 5'-nucleotidase acquired deficiency in beta-thalassemia: involvement of enzyme-SH groups in the inactivation process. 211 21

Of the various species of cellular 5'-nucleotidases, membranous, lysosomal and cytosolic, only the latter are likely to play a role in the physiologic dephosphorylation of the 5'-nucleoside monophosphates present in the cytoplasm. The necessity to preserve cellular ATP renders a strict control of the dephosphorylation as well as of the deamination of AMP mandatory, because both nucleotides are maintained in equilibrium by adenylate kinase. Our studies of cytosolic purine 5'-nucleotidases purified from rat liver and from human erythrocytes, reviewed in this presentation, have shown that both display complex kinetic properties. Both enzymes have markedly higher affinities for IMP and for GMP than for AMP. In addition, they are stimulated by nucleoside triphosphates, among them ATP and GTP, and inhibited by Pi. The erythrocytic purine 5'-nucleotidase is also stimulated by glycerate 2,3-bisphosphate. It could thus be expected that under conditions of ATP and GTP breakdown, particularly when accompanied by an increase in Pi, the dephosphorylation of AMP would be curtailed. To verify this hypothesis, experiments were performed with isolated rat hepatocytes and with human red blood cells. The rate of dephosphorylation of AMP was measured by following time-wise the production of adenosine in the presence of coformycin (or deoxycoformycin) and 5-iodotubercidin. The coformycins inhibit the deamination of adenosine into inosine by adenosine deaminase, and 5-iodotubercidin inhibits the recycling of adenosine into AMP by adenosine kinase. Upon induction of ATP catabolism by the addition of fructose to isolated rat hepatocytes, the dephosphorylation of AMP was nearly completely suppressed. In accordance with these results, the activity of the rat liver cytosolic 5'-nucleotidase, assayed in the presence of concentrations of substrate and effectors mimicking those measured in intact cells following the addition of fructose, was decreased as compared to control conditions. In hepatocytes in which ATP catabolism was induced by suppression of oxygen, the rate of dephosphorylation of AMP increased about 3-fold. However, in contradiction with these data, the activity of the cytosolic 5'-nucleotidase, measured under conditions mimicking anoxia, decreased markedly. In human erythrocytes, dephosphorylation of AMP did not occur under physiologic conditions, but proceeded when ATP catabolism was induced by glucose lack or by alkalinization. The rate of dephosphorylation of AMP was 3-fold higher during glucose deprivation than under alkaline conditions.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Cytosolic purine 5'-nucleotidases of rat liver and human red blood cells: regulatory properties and role in AMP dephosphorylation. 285 49

The salivary apyrase activity of the blood-sucking bug Rhodnius prolixus was found to reside in a true apyrase (ATP diphosphohydrolase, EC 3.6.1.5) enzyme. The crude saliva was devoid of 5'-nucleotidase, inorganic pyrophosphatase, phosphatase and adenylate kinase activities. ATP hydrolysis proceeded directly to AMP and Pi without significant accumulation of ADP. Km values for ATP and ADP hydrolysis were 229 and 291 microM respectively. Ki values for ATP and ADP inhibition of ADP and ATP hydrolysis were not different from the Km values, and these experiments indicated competitive inhibition. Activities were purified 126-fold by combined gel filtration and ion-exchange chromatography procedures with a yield of 63%. The purified enzyme displayed specific activities of 580 and 335 mumol of Pi released/min per mg of protein for ATP and ADP hydrolysis respectively. The action of the purified enzyme on several phosphate esters indicates that Rhodnius apyrase is a non-specific nucleosidetriphosphate diphosphohydrolase.
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PMID:Salivary apyrase of Rhodnius prolixus. Kinetics and purification. 301 Sep 45

Three catabolic enzymes, 5'-nucleotidase (5'NT), adenosine deaminase (ADA), purine nucleoside phosphorylase (PNP) and one anabolic enzyme, myokinase (MK) involved in adenine nucleotide (AN) metabolism were studied in myocardium from 4 to 105 day old rats. The specific enzyme activities (nmoles/min/mg protein) at day 4 were 35.3 for 5'NT, 28.4 for ADA, 43.3 for PNP, and 5 X 10(3) for MK. At day 7, 5'NT, activities rose to 450%; PNP and ADA 150%; and MK 120%; of the day 4 level. The activities of the three catabolic enzymes were elevated for one or two weeks then declined rapidly. By day 34, they were slightly above the adult values. MK activity displayed a different time course. It continued to increase slowly with age after the initial surge. Compared to the adult heart, the total activities of these catabolic enzymes in the one- to three-week-old heart were 30% to 220% higher. This transient elevation in AN catabolic enzyme activities may be related to active DNA synthesis and cell proliferation occurred in the rat myocardium during the same period.
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PMID:Postnatal changes in enzyme activities of rat myocardial adenine nucleotide catabolic pathway. 302 44

The loss of the catabolic products of adenosine triphosphate in the form of purine nucleosides and oxypurines during ischemia and subsequent reperfusion may limit adenine nucleotide regeneration. This study compared the effects of infusion of inhibitors of the major reactions involved in the degradation of adenosine triphosphate to inosine on the postischemic recovery of high energy phosphate and myocardial function. Isolated rat hearts were made totally ischemic after a 5-min infusion of p1,p5-diadenosine pentaphosphate, alpha, beta-methylene adenosine diphosphate, nitrobenzyl-6-thioinosine, or erythro-9-(2-hydroxy-3-nonyl) adenine, which are inhibitors of adenylate kinase, 5'-nucleotidase, adenosine translocase, and adenosine deaminase, respectively. Following 30 min of ischemia, only hearts infused with alpha, beta-methylene adenosine diphosphate recovered significantly better ventricular function than did the control (P less than 0.05), but all hearts had increased adenosine triphosphate and creatine phosphate regeneration (P less than 0.05). The formation and washout of greater than 30% of the total adenine pool metabolites were not prevented by any drug. Nevertheless all manipulations of adenine metabolism resulted in recruitment of high energy phosphate during preischemic infusion which may have potential benefits in elective ischemic arrest.
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PMID:Influence of inhibitors of ATP catabolism on myocardial recovery after ischemia. 304 Nov 5


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