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:3.5.4.4 (adenosine deaminase)
5,136 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Adenosine deaminase, a purine metabolic enzyme, was studied in lymphoid tissues of the developing chicken in order to evaluate whether enzyme activity is related to development of the immune system in birds in the same way as for mammals, in which adenosine deaminase is essential for lymphocyte differentiation, especially for the T-cell lineage. Enzyme activity was assayed in thymocytes and bursal lymphocytes at different times during chicken development ranging from the 17th day of embryonic life up to the 50th day after hatching. Adenosine deaminase activity was significantly higher in the bursa than in the thymus, regardless of whether such an activity was expressed per mg protein or per 10(8) cells; moreover, no substantial difference in the relative levels of adenosine deaminase was observed in thymocytes at the various stages of thymus development studied. Significant changes in enzyme activity, however, were found in bursal lymphocytes in which different amounts of adenosine deaminase appeared to be related to definite stages of bursal development and to specific immunological responsiveness of B lymphocytes to intravenously injected antigens. Therefore, if adenosine deaminase does play a role in the functional maturation of the immune system in birds, such a role appears to be related to the differentiation of the B- rather than the T-cell lineage.
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PMID:Questioning the role of adenosine deaminase in the development of B lymphocytes in chicken bursa. 233 59

The enzyme activities of S-adenosylhomocysteine hydrolase, adenosine deaminase and pyruvate kinase were determined in normal human erythrocytes subpopulations of different ages separated by centrifugation on a discontinuous Percoll:NaCl density gradient. The levels of S-adenosylhomocysteine hydrolase activity were found to undergo a sharp decrease with red cell ageing. Adenosine deaminase activities were, however, less critically dependent on erythrocyte age.
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PMID:S-adenosylhomocysteine hydrolase and adenosine deaminase activities in human red cell ageing. 238 22

Adenosine deaminase was estimated in ascitic fluids of 49 patients with ascites (19 tuberculous, 20 cirrhotic, and 10 malignant). The adenosine deaminase concentration in tuberculous ascitic fluid was 98.8 +/- 20.1 U/L (mean +/- SD), which was significantly more than that noted in cirrhotic (14 +/- 10.6 U/L) or malignant (14.6 +/- 6.7 U/L) ascitic fluids (p less than 0.001 for each). At a cut-off value of greater than 33 U/L, the sensitivity, specificity, positive and negative predictive value, and the overall diagnostic accuracy for diagnosing tuberculous ascites were 100%, 96.6%, 95%, 100%, and 98%, respectively. We conclude that estimation of adenosine deaminase in ascitic fluid is an easy and reliable method for diagnosing tuberculous ascites.
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PMID:Value of adenosine deaminase estimation in the diagnosis of tuberculous ascites. 238 24

Stimulation of sympathetic fibers or infusion of norepinephrine (NE) into the superior mesenteric artery (SMA) leads to an initial decrease in intestinal blood flow, which is followed by a return of flow toward the base-line value (autoregulatory escape) despite continued nerve stimulation or NE infusion. Although the mechanisms responsible for "autoregulatory escape" have not been defined, accumulation of vasodilator metabolites is frequently invoked to explain this phenomenon. Inasmuch as histamine and adenosine exist in high concentrations in the intestinal mucosa and both are potent vasodilators, we examined the effects of chlorpheniramine (an H1 blocker) and adenosine deaminase (degrades adenosine) on autoregulatory escape from NE infusion. In autoperfused piglet intestinal preparations, we measured SMA blood flow and the arteriovenous oxygen difference during intra-arterial NE infusion before and after blockade with chlorpheniramine or adenosine deaminase. Adenosine deaminase pretreatment increased the peak vasoconstrictor and reduced the steady-state escape responses to NE infusion. Chlorpheniramine did not affect either the vasoconstrictor or escape responses. The oxygen uptake changes induced by NE infusion were not dramatically modified by either treatment. These results indicate that adenosine but not histamine is responsible for at least part of the escape of intestinal blood flow from NE infusion.
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PMID:Autoregulatory escape from norepinephrine infusion: roles of adenosine and histamine. 245 33

The distribution and morphology of adenosine deaminase, substance P, leucine-enkephalin, corticotropin-releasing factor, and calcitonin gene-related peptidelike immunoreactive cells and fibers throughout the superior colliculus of the rat were examined by means of the unlabelled-antibody peroxidase-antiperoxidase method. Adenosine deaminase immunoreactive cells were found in the stratum opticum and lower stratum griseum superficiale; substance P immunoreactive cells were localized to the upper stratum griseum superficiale, and calcitonin gene-related peptide immunolabelled neurons were situated in deeper strata. Substance P, leucine-enkephalin, and calcitonin gene-related peptide immunoreactive fibers were distributed similarly in their lamination and in their patchlike organization. Corticotropin-releasing factor immunoreactive fibers were observed evenly throughout all the strata and were fewer in the stratum griseum superficiale. These findings suggest that, as in afferent modules and segregated efferents of the mammalian superior colliculus, the cells and fibers containing neuroactive substances and neuroactive substance-related enzymes also show a segregated and laminar distribution.
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PMID:Laminar and segregated distribution of immunoreactivities for some neuropeptides and adenosine deaminase in the superior colliculus of the rat. 246 26

Effects of erythro-9(2-hydroxy-3-nonyl) adenine (EHNA), an inhibitor of the common Adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4.), on HIV-1 production was evaluated in vitro. Reverse transcriptase (RT) activity in the supernatant was inhibited by nearly 50% in EHNA-treated HIV-1 infected H9 cells, when compared with untreated but infected H9 cells. There was also a significant decrease in cell viability, but this was reversed following the addition of deoxycytidine (dC) to these cultures. The combined treatment was also effective in suppressing HIV-1 release from HIV-1-infected U937 cells. This combined EHNA plus dC treatment had no effect on RT activity in the cell lysates, suggesting that the inhibition of HIV-1 production may be due to the disturbance of virus release from infected cells.
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PMID:Evaluation of the effects of erythro-9(2-hydroxy-3-nonyl) adenine (EHNA) on HIV-1 production in vitro. 247 29

Adenosine deaminase and 5'-nucleotidase activities as well as chemiluminescence emission were measured in peritoneal macrophages of Syrian hamsters in the growth process of tumours with different grade of malignancy. The adenosine deaminase activity was established to decrease, while the 5'nucleotidase activity--to increase in macrophages after the subcutaneous injection of tumour cells with high level of malignancy as compared with these values in normal cells. This is accompanied by a decrease of the macrophage chemiluminescence during the whole experimental period. At the same time adenosine deaminase and 5'-nucleotidase activities as well as chemiluminescence emission in peritoneal macrophages of hamsters treated with low-malignancy cells do not differ from these values in the control group.
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PMID:[Activity of adenosine metabolism enzymes and spontaneous chemiluminescence in macrophages in the tumor growth process]. 254 8

Enzyme activities were studied in peripheral blood lymphocytes from patients infected with, or at risk for, infection with human immunodeficiency virus (HIV). No significant differences were observed in the HIV-infected and HIV-seronegative high-risk patients with regard to enzyme activities of hypoxanthine-guanine phosphoribosyltransferase (EC 2.4.2.8) and purine nucleoside phosphorylase (EC 2.4.2.1) in peripheral blood. Adenosine deaminase (EC 3.5.4.4) was significantly (P less than 0.02) depressed in asymptomatic HIV-seropositive patients and HIV-seronegative patients at high risk of HIV infection as compared with a healthy HIV-seronegative population. Adenosine kinase (AK, EC 2.7.1.20) was significantly increased in the asymptomatic seropositive (P less than 0.02) and also in the HIV-seronegative high-risk groups (P = 0.01) compared with the normal controls. AK activity was significantly lower in subjects with AIDS than in the asymptomatic (P less than 0.002) and high-risk groups (P less than 0.01). Taken together, these results indicate that adenosine deaminase and AK activities are influenced by the health of the patient, and that measurement of AK activity may prove useful in monitoring the clinical progress of patients with HIV infection.
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PMID:Depressed activities of purine enzymes in lymphocytes of patients infected with human immunodeficiency virus. 254 31

Adenosine deaminase was found to bind 6-hydroxy-1,6-dihydropurine ribonucleoside (II), formed by reversible addition of water to purine ribonucleoside (I) in a reaction analogous to formation of a tetrahedral intermediate in substrate deamination, with an apparent Ki value of 3 x 10(-13) M at 20 degrees C. 1,6-Dihydropurine ribonucleoside (IV), synthesized by photolysis of purine ribonucleoside in the presence of NaBH4, exhibited a Ki value of 5.4 x 10-6 M. After correction for differences between the relative free energies of solvation of II and IV, the 6-hydroxyl group of II was estimated to contribute more than 16 kcal to the free energy of binding, approaching the enthalapy of formation of a single hydrogen bond to charged group in the vapor phase. The relatively weak binding of IV and of substrate water suggests that entropic effects, arising from the cooperative action of binding determinants contained within these separate molecules, contribute more than 10 kcal/mol to the free energy of binding of II in which these binding determinants are contained within a single molecule. In free solution, the entropy of reversible hydration of I was evaluated by measuring the temperature dependence of equilibria of protonation of I and of pseudobase formation from I-methylpurinium ribonucleoside as -35 eu, comparable with the entropy of activation for the uncatalyzed hydrolysis of adenosine. In the active site of adenosine deaminase, this thermodynamic obstacle is evidently climbed spontaneously as a result of attractive interactions between the active site and the critical hydroxyl group at the 6-position.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Contribution of a single hydroxyl group to transition-state discrimination by adenosine deaminase: evidence for an "entropy trap" mechanism. 255 14

Adenosine deaminase, a purine salvage enzyme essential for immune competence, was studied by time-resolved fluorescence spectroscopy. The heterogeneous emission from this four-tryptophan protein was separated into three lifetime components: tau 1 = 1 ns and tau 2 = 2.2 ns an emission maximum at about 330 nm and tau 3 = 6.3 ns with emission maximum at about 340 nm. Solvent accessibility of the tryptophan emission was probed with polar and nonpolar fluorescence quenchers. Acrylamide, iodide, and trichloroethanol quenched emission from all three components. Acrylamide quenching caused a blue shift in the decay-associated spectrum of component 3. The ground-state analogue enzyme inhibitor purine riboside quenched emission associated with component 2 whereas the transition-state analogue inhibitor deoxycoformycin quenched emission from both components 2 and 3. The quenching due to inhibitor binding had no effect on the lifetimes or emission maxima of the decay-associated spectra. These observations can be explained by a simple model of four tryptophan environments. Quenching studies of the enzyme-inhibitor complexes indicate that adenosine deaminase undergoes different protein conformation changes upon binding of ground- and transition-state analogue inhibitors. The results are consistent with localized structural alterations in the enzyme.
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PMID:Time-resolved fluorescence spectroscopy of human adenosine deaminase: effects of enzyme inhibitors on protein conformation. 271 44


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