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)

Activities of several adenosine metabolizing enzymes were examined in capillary preparations isolated from rabbit ventricle. Vmax and Km values for 5'-nucleotidase were 2.3 nmol/min/mg and 10 microM, respectively. For adenosine deaminase the corresponding values were 7.8 nmol/min/mg and 32 microM. S-adenosyl-homocysteine hydrolase, which forms adenosine by the hydrolysis of S-adenosylhomo-cysteine, was also present (Vmax, 0.07 nmol/min/mg; Km, 0.81 microM), as were adenosine kinase (Vmax, 0.2 nmol/min/mg; Km, 0.52 microM) and purine nucleoside phosphorylase (Vmax, 13.8 nmol/min/mg; Km, 96 microM). These enzymes were also present in microvessels (capillaries and arterioles) purified from rabbit brain. Activities of several enzymes, especially 5'-nucleotidase and adenosine deaminase, were much lower in myocytes isolated from rabbit ventricle. The study provides evidence that endothelial cells of the microvasculature from heart and brain are capable of activity forming and degrading adenosine. It is possible that adenosine formed by these cells may contribute to the local regulation of blood flow.
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PMID:Adenosine metabolism in microvessels from heart and brain. 300 95

WI-L2 cells (a B-lymphoblastoid cell line) were more resistant than CEM cells (a T-lymphoblastoid cell line) to deoxyadenosine, ara-A (9-beta-D-arabinofuranosyladenine), or ara-C (1-beta-D-arabinofuranosylcytosine) inhibition. This was caused by a difference in the composition of cytosol 5'-nucleotidases between WI-L2 and CEM cells. In intact cells, the endogenous production of deoxyadenosine from WI-L2 cells deficient in adenosine kinase (EC 2.7.1.20) and deoxycytidine kinase (EC 2.7.1.74) was consistently high, despite changes in endogenous adenosine production. Endogenous production of deoxyadenosine from CEM cells deficient in adenosine kinase and deoxycytidine kinase was, however, coordinated with endogenous adenosine production. In broken cells, cytosol dAMPase (2'-deoxyadenosine 5'-monophosphate 5'-nucleotidase) activity of WI-L2 cells was 3-5-fold higher than that of CEM cells. dAMPase activity could be separated from ATP-activated IMPase (inosine 5'-monophosphate 5'-nucleotidase) by gel filtration (molecular weight: dAMPase; 39,000-46,000; ATP-activated IMPase, greater than 150,000). Cytosol ATP-activated IMPase and dAMPase were isolated by phosphocellulose or DEAE-Bio-Gel A chromatography from non-specific phosphatases. The ATP-activated IMPase showed only marginal activity towards dAMP (2'-deoxyadenosine 5'-monophosphate), ara-AMP (9-beta-D-arabinofuranosyladenine 5'-monophosphate), or ara-CMP (cytosine-beta-D-arabinofuranoside 5'-monophosphate), even in the presence of ATP. The activity of ATP-activated IMPase was similar in WI-L2 and CEM cells. dAMPase was separated into two peaks by DEAE-Bio-Gel A chromatography; one of these peaks degraded ara-AMP and ara-CMP. The activities of both peaks from WI-L2 cells were higher than those from CEM cells. These results show that the degradation of dAMP, ara-AMP or ara-CMP was more specific and rapid in WI-L2 than in CEM cells.
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PMID:Differential composition of cytosol 5'-nucleotidases between T and B lymphoblasts. 301 Nov 14

Long-term bovine lymphocyte cultures were initiated by stimulation with alloantigens and maintained in continuous culture using medium containing recombinant human interleukin-2 (rh IL-2). The development of specific and lectin-dependent killing was monitored following primary alloantigen challenge. Cytolytic activity was barely detectable after 7 days of culture, but gradually increased with peak activity occurring after 21 days of culture. A panel of monoclonal antibodies (MoAb) was used to determine whether a shift in the antigen phenotype of the cell population occurred during culture. The primary cell type that grew in culture was of the T-cell lineage with minimal or no expression of class II antigens. The activities of adenosine deaminase (ADA), purine nucleotide phosphorylase (PNP), adenosine kinase (AK), deoxyadenosine kinase (dAK), deoxycytidine kinase (dCK), 5'-nucleotidase (5'-N), AMP deaminase, hypoxanthine-guanine phosphoribosyl transferase (HGPRT or HPRT), and adenine phosphoribosyl transferase (APRT) were measured by microassay in resting peripheral blood lymphocytes (PBL) and in cells from long-term cultures. Large increases in the activities of PNP and HPRT with a decrease in the activity of ADA were observed. The data show that long-term cultures of lymphocytes can be readily generated, and that sequential changes in antigenic phenotype and function can be monitored and correlated with quantitative changes in enzyme activity.
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PMID:Development and maintenance of bovine cytotoxic lymphocytes with recombinant human interleukin-2. 348 20

The relative cytotoxicity of 9-beta-D-arabinofuranosyladenine and 9-beta-D-arabinofuranosyladenine 5'-monophosphate (ara-AMP) were compared using wild-type and adenosine kinase (AK)-deficient baby hamster kidney somatic cell mutants. The cytotoxicity of ara-AMP to baby hamster kidney cells was dependent on the presence of AK activity since AK-deficient mutants were resistant to ara-AMP. On an equimolar basis, ara-AMP was consistently less cytotoxic than was 9-beta-D-arabinofuranosyladenine to wild-type and AK-deficient baby hamster kidney mutant cells. These findings are consistent with the common view that ara-AMP molecules do not enter mammalian cells as an intact nucleotide. Presumably, ara-AMP molecules were hydrolyzed by the nonspecific phosphatases and 5'-nucleotidase found in the serum or by the ecto-5'-nucleotidase on the outer surface of the membrane and only enter the mammalian cells as 9-beta-D-arabinofuranosyladenine.
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PMID:Relative cytotoxicity of 9-beta-D-arabinofuranosyladenine and 9-beta-D-arabinofuranosyladenine 5'-monophosphate. 616 44

Adenosine 5'-triphosphate (ATP) was catabolized by whole cells and cell-free extracts of Rickettsia typhi to adenosine 5'-diphosphate (ADP) and then to adenosine 5'-monophosphate (AMP), the end product of ATP catabolism under the experimental conditions used. The only intermediate of the pathway from ATP to AMP which was identified by thin-layer chromatography and quantitated by the (14)C content was ADP, whereas products such as adenine, adenosine, hypoxanthine, inosine, and inosine 5'-monophosphate were not detected. The enzymes which could be theoretically responsible for the catabolism or the anabolism of AMP were not detected by standard assay procedures. Most importantly, 5'-nucleotidase or nonspecific phosphatase and AMP nucleosidase activities were undetectable under a variety of experimental conditions. Although these two enzymes remove AMP from the adenylate pool in other cells, they are apparently nonfunctional in R. typhi. The biosynthesis of ATP was initiated by adenylate kinase because no adenine phosphoribosyltransferase or adenosine kinase could be detected. Furthermore, AMP was transported intact without prior dephosphorylation. These observations suggest that for R. typhi the in vivo activity of adenine nucleotide interconversion was limited to the nucleotides, with AMP being the end product of ATP catabolism, and that the salvage of purine bases and nucleosides was not an essential feature of purine metabolism. These results elucidate the findings of a previous study which showed that in the absence of glutamate as a source of energy, the adenylate energy charge of resting cells of R. typhi is drastically lowered by the high proportion of AMP.
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PMID:Adenine nucleotide degradation by the obligate intracellular bacterium Rickettsia typhi. 624 88

A methodology is presented for systemic analysis of purine enzymes in small lymphocyte subfractions. For the determination of 7 different enzymes of purine metabolism *hypoxanthine-guanine phosphoribosyltransferase (HG-PRT), adenine phosphoribosyltransferase (A-PRT), adenosine deaminase (ADA), purine nucleoside phosphorylase (PNP), adenosine kinase (AK), 5'-nucleotidase (5'N), and AMP-deaminase) less than 200,000 peripheral blood lymphocytes are needed. 1000-6000 lyophilised lymphocytes are incubated in micro-incubation vessels (3 microliter) with radioactive substrates for 15-180 min. Separation of substrates and products is achieved by thin-layer chromatography on PEI-cellulose. Addition of BSA to the incubation mixtures results in higher specific enzyme activities and narrower ranges of mean values of a control group.
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PMID:Enzymes of purine nucleotide metabolism in human lymphocytes. 625 89

In an attempt to further define the site of myocardial adenosine formation, isolated guinea pig hearts were perfused with potent inhibitors of 5'-nucleotidase [alpha, beta-methylene adenosine 5'-diphosphate (AOPCP)] and of nucleoside transport [4-nitrobenzyl thioinosine (NBMPR)]. AOPCP (50 microM) inhibited the activity of cardiac ecto-5'-nucleotidase by 85% but did not influence the release of adenosine, inosine, and hypoxanthine formed at an accelerated rate by the heart during hypoxic perfusion (30% O2). In contrast, NBMPR (5 microM) diminished the hypoxia-induced release of adenosine and its degradatives and greatly potentiated the increase of myocardial tissue levels of respective purine compounds. Studies carried out with 5'-deoxyadenosine, an adenosine derivative that is not metabolized, indicate NBMPR to inhibit both uptake and release of adenosine in the isolated heart and in human erythrocytes. Cell fractionation studies on guinea pig ventricular muscle revealed that 5'-nucleotidase, though mainly associated with the membrane fraction, is also found in the cardiac cytosol (200,000-g supernatant), exhibiting a different substrate specificity. Furthermore, S-adenosylhomocysteine hydrolase as well as adenosine kinase and adenosine deaminase proved to be exclusively present in the cytosolic fraction. Our findings suggest that in the hypoxic heart a) ecto-5'-nucleotidase most likely is not involved in the formation of adenosine, b) release of adenosine from the heart requires adenosine to be transported across the sarcolemma membrane, and c) adenosine is predominantly formed intracellularly, a process involving cytosolic 5'-nucleotidase and/or S-adenosylhomocysteine hydrolase.
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PMID:Different sites of adenosine formation in the heart. 626 1

Rat adipose tissue was digested with collagenase and separated into adipocytes and stromal-vascular cells. The adipocytes accounted for 40% of the total adipose tissue adenosine deaminase activity, 32% of 5'-nucleotidase activity and 87% of adenosine kinase activity. This distribution suggests that adipocyte are the major cell type involved in adenosine utilization in adipose tissue. Furthermore, it suggests that the high sensitivity of isolated adipocytes to adenosine is representative of their sensitivity of isolated adipocytes to adenosine is representative of their sensitivity in vivo.
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PMID:Distribution of adenosine metabolising enzymes between adipocyte and stromal-vascular cells of adipose tissue. 626 98

Adenosine synthesis was studied during 2-deoxyglucose-induced ATP catabolism in intact rat polymorphonuclear leucocytes. When both adenosine kinase (EC 2.7.1.20) and adenosine deaminase (EC 3.5.4.4) were selectively inhibited, adenosine accumulated. Adenosine formation took place inside the intact cells by a metabolic pathway independent of the ecto-5'-nucleotidase (EC 3.1.3.5). Distinct metabolic pathways are proposed for adenosine production from intracellular or extracellular nucleotides.
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PMID:Adenosine production inside rat polymorphonuclear leucocytes. 628 Jun 85

The adenosine kinase activity present in a soluble preparation from rat liver was investigated using formycin A (FoA), a fluorescent analog of adenosine as the phosphoryl acceptor and ATP as the donor. Reversed-phase high-performance liquid chromatography (h.p.l.c.) was used to separate substrate from product, and the progress of the phosphorylation reaction was followed by monitoring fluorometrically the amount of formycin 5'-monophosphate (FoMP), and the AMP analog, that was formed. The results showed that while FoMP was formed during the reaction indicating that an adenosine kinase activity was present, both formycin 5'-di- and triphosphate (FoDP and FoTP respectively), the corresponding analogs of ADP and ATP, were also formed, suggesting than an adenylate kinase activity was present. This result was confirmed with FoMP as the substrate and showing the formation of FoDP and FoTP. Other experiments carried out with FoMP as the substrate revealed the formation of FoA. Taken together, these results indicated that a 5'-nucleotidase activity as well as an adenylate kinase was present. Using this analog and h.p.l.c., it has been possible to demonstrate for the first time in an in vitro system the complete salvage of a nucleoside to the triphosphate level.
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PMID:In vitro processing of the adenosine analog formycin A to the mono-, di-, and triphosphate by a soluble multienzyme system from mouse liver. 628 Jul 86


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