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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

A simple method is presented for the determination of pyrimidine-5'-nucleotidase activity using a continuous spectrophotometric assay system. Activity is determined by measuring inorganic phosphate generation using a linked indicator system that produces uric acid in the presence of inosine, purine nucleoside phosphorylase, and xanthine oxidase. This method has several advantages over any of the methods currently in use.
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PMID:A continuous spectrophotometric assay for pyrimidine-5'-nucleotidase. 300 35

The activity of guanine deaminase (GAH, E.C.3.5.4.3) was lower in rat cerebellum soluble and microsomal fractions than in rat brain subfractions. Adenosine deaminase (ADA, E.C.3.5.4.4) activity was released in higher proportion than guanine deaminase, purine nucleoside phosphorylase (PNP, E.C.2.1.2.4), 5'-nucleotidase (5'N, E.C.3.1.3.5), and lactate (LDH, E.C. 1.1.1.27) and malate (MDH, E.C. 1.1.1.37) dehydrogenase in press-juices of rat brain. Furthermore, nerve ending-derived fractions (synaptosomes and synaptic vesicles) showed an enrichment of adenosine deaminase and also of 5'-nucleotidase. The action of deoxycholate over the subfractions did not increase the activity of either enzyme. The contrary occurred with the remaining enzymes studied. Thus, it is possible that one set of enzymes are located on the surface of the particulate vesicles, whereas another set are located inside these vesicles, suggesting a compartmentation of purine catabolic enzymes in different areas of the central nervous system.
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PMID:Heterogeneous localization of some purine enzymes in subcellular fractions of rat brain and cerebellum. 301 Jan 50

Differences in activities of the purine degradative enzymes, adenosine deaminase (ADA), purine nucleoside phosphorylase (PNP), and 5'-nucleotidase (5'NT), have been observed among different classes of lymphoid malignancies. Recent studies have shown that hairy cell leukemia (HCL) may respond to treatment with the ADA inhibitor, 2-deoxycoformycin. This study demonstrates that the cells of HCL have significantly lower levels of ADA and 5'NT (P always less than 0.01) when compared to levels in normal B- or T-lymphocytes, but have higher levels of PNP (P less than 0.001 for both comparisons). Recent studies have shown that when treated with 12-O-tetradecanoyl-phorbol-13-acetate (TPA), cells of B-cell chronic lymphatic leukemia (B-CLL) acquire phenotypic characters of HCL. The authors have therefore also investigated the changes in enzyme pattern of B-CLL after incubation with TPA B-CLL cells are characterized by low levels of ADA, PNP, and 5'-NT, but TPA caused a marked increase in PNP activity (P less than 0.001, t test for paired samples), a pattern similar to HCL. The results from biochemical studies are thus in accordance with the hypothesis that HCL cells are more mature than B-CLL cells. The special enzyme profile of HCL suggests that a PNP inhibitor might also be effective in the treatment of this disease.
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PMID:Enzymes of purine metabolism in hairy cell leukemia. 301 Dec 39

Suspensions of rat brain microsomes, synaptosomes, and synaptic vesicles were able to convert adenosine to inosine by means of adenosine deaminase. Isosbestic points of this transformation, at 222, 250 and 281 nm, remained unchanged with time-course. This fact suggests that adenosine deaminase (ADA, E.C. 3.5.4.4) is located on the surface of the vesicles whereas purine nucleoside phosphorylase (PNP, E.C. 2.1.2.4) is located inside the vesicles. Kinetic parameters of the particulate 5'-nucleotidase (5'N, E.C. 3.1.3.5) and adenosine deaminase were analogous to those of the cytosolic enzymes. These results suggest that soluble and particulate enzymes represent different pools of the same molecular species.
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PMID:Kinetics of the 5'-nucleotidase and the adenosine deaminase in subcellular fractions of rat brain. 301 60

Activities of key enzymes of purine metabolism [adenosine deaminase (AD); purine nucleoside phosphorylase (PNP); 5'-nucleotidase] were studied; changes in DNA content, nucleus ploidity in thymocytes, T- and B-lymphocytes in the C3HA mouse spleen during solid 22 hepatoma growth and after the immunization were monitored. Immunological properties of lymphocytes were also investigated measuring antibody formation and the reaction of blasttransformation in response to phytohemagglutinin, concanavalin A and lipopolysaccharide. Within the first 48 hrs after the tumor implantation and immunization certain nonspecific biochemical mechanisms of lymphocytes activation (elevated AD activity, decreased activity of 5'-nucleotidase, augmented intracellular DNA levels, polyploidity) were revealed. As the solid 22 hepatoma reached the maximum growth rate specific alterations in the activities of the purine metabolism key enzymes were observed reflecting the response of thymus and spleen lymphocytes to the presence of the malignant tumor.
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PMID:[Biochemical and functional characteristics of thymus and spleen lymphocytes in C3HA mice during the growth of hepatoma 22 and after immunization with sheep erythrocytes]. 302 Jul 91

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

5'-Nucleotidase which was found first in chicken liver and found to be located in cytosol was purified and characterized. This enzyme is termed cytosol 5'-nucleotidase for convenience. Some properties of this enzyme are summarized in Table 7. (Table: see text) The specific activity of cytosol 5'-nucleotidase in chicken liver cytosol is higher than that in rat liver cytosol. In response to a high protein diet the activity of cytosol 5'-nucleotidase in chicken liver increased, concurrently with those of purine nucleoside phosphorylase and xanthine dehydrogenase. Of the three enzymes, the activity of cytosol 5'-nucleotidase reached a maximum most rapidly. In rat liver, the activities of these three enzymes did not increase on administration of a high protein diet. From these results the principal physiological function of the cytosol 5'-nucleotidase is assumed to be dephosphorylation of IMP as the first step in the pathway of uric acid formation from IMP, which is important in the elimination of nitrogen of amino acids and proteins in a uricotelic animal. An allosteric property of this enzyme is considered to be important for control of adenine and guanine nucleotide pools, especially in connection with the biosynthetic activity of the purine nucleotides in uricotelic animals.
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PMID:Properties of cytosol 5'-nucleotidase and its role in purine nucleotide metabolism. 302 48

The pathways of adenine nucleotide catabolism were investigated in cultured beating cardiomyocytes. The activity of the enzymes involved in AMP degradation was assayed in cell extracts. Fluxes of label from ATP to the various purine derivatives were measured in intact cells. Under physiological conditions, cells degraded AMP through deamination to IMP. IMP was rapidly degraded to inosine, hypoxanthine, xanthine and uric acid, which were effluxed from the cells. This is in accord with the fact that the activity of AMP deaminase (EC 3.5.4.6) was 7-fold that of AMP 5'-Nucleotidase (EC 3.1.3.5). Mild ATP-degradation, induced by inhibition of glycolysis by iodoacetate, caused no alterations in the degradation pathways (more than 85% through deamination to IMP). However, fast ATP-degradation (83% of adenine nucleotides/10 min), induced by simultaneous inhibition of glycolysis and electron transport (by antimycin A), caused increased dephosphorylation of AMP to adenosine (50% of total AMP-degradation). The cardiomyocyte extracts were found to contain a significant activity of purine nucleoside phosphorylase (EC 2.4.2.1). Despite the presence of hypoxanthine-guanine phosphoribosyltransferase (EC 2.4.2.8), salvage of hypoxanthine to IMP, both at physiological as well as at conditions associated with ATP degradation, was slow. The salvage of adenosine appeared to be efficient at physiological conditions, but not at fast rates of ATP degradation.
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PMID:Pathways of adenine nucleotide catabolism in primary rat cardiomyocyte cultures. 325 63

Purine and pyrimidine enzyme profiles of human cell lines have been investigated. A novel observation was the finding that most of the cell lines showed very low or undetectable levels of cytidine (deoxycytidine) deaminase, while they possessed pyrimidine 5'-nucleotidase, cytidine and deoxycytidine kinase activities. Most cell lines showed high levels of adenosine deaminase and purine nucleoside phosphorylase activities and low levels of purine 5'-nucleotidase. We propose that high adenosine deaminase and purine nucleoside phosphorylase activities and low cytidine deaminase activity may be of importance for immature hematopoietic cells in order to ensure a balanced synthesis of the DNA precursors.
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PMID:Low cytidine deaminase levels in human hematopoietic cell lines. 362 11


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