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)

Exogenous adenosine triphosphate (ATP) added to brush-border membrane vesicles was rapidly degraded mainly to inosine according to the high ecto-nucleotidase activities in these vesicles. In the absence of phosphate, inosine was slowly transformed into hypoxanthine, and xanthine oxidase and dehydrogenase activities were not detected. The presence of ecto-adenosine deaminase and ecto-adenosine monophosphate (AMP) nucleotidase was shown. The ecto-adenosine deaminase was inhibited by deoxycoformycin and was also detected in rat renal brush-border membrane vesicles. Using orthovanadate, levamisole, and alpha, beta-methylene adenosine diphosphate as possible inhibitors, alkaline phosphatase was shown to be the main agent responsible for ecto-AMP nucleotidase activity. In pig renal basolateral membrane vesicles and in whole cell extracts from pig renal cortex, ecto-AMP nucleotidase was the limiting factor in ATP degradation. Comparing the ATP catabolism in the whole cell cortical extract with the catabolism in the same sample precleared of membranes, it was shown that ectonucleotidase activity is mainly bound to the membranous components. It is also shown that the whole cell extract of pig renal cortex has hypoxanthine phosphoribosyl transferase activity, and it seems probable that the rapid and specific formation of luminal inosine and its transport into the cell in competition with adenosine may start the purine salvage pathway through the synthesis of IMP from hypoxanthine.
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PMID:Adenine nucleotides and adenosine metabolism in pig kidney proximal tubule membranes. 840 44

Experiments on 24 Wistar male rats were performed to clarify the role of central mechanisms in the onset of electrical instability of the heart due to disturbances in purine metabolism. The activity of the enzymes responsible for synthesis and conversion of adenosine-5-nucleotidase and adenosine deaminase in the sensomotor cortex, hypothalamus and hippocamp was studied. Changes in cardiac function were most severe in high levels of adenosine in the neurons of the sensomotor cortex, hypothalamus and hippocamp. Minimal changes occurred in low content of adenosine in the hypothalamus and hippocamp.
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PMID:[Effect on cardiac function of altered adenosine metabolism in rat brain structures in modelled hyperuricemia]. 963 94

Activities of adenosine deaminase (ADA), 5'nucleotidase (5'NT), xanthine oxidase (XO), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) and levels of thiobarbituric acid reagent substances (TBARS) were measured in 10 cancerous and 10 noncancerous human prostate tissues. Decreased activities of DNA turnover enzymes (ADA and 5'NT), increased activities of GSH-Px and CAT, and unchanged activities of SOD and XO were observed in cancerous prostate tissues compared with those of noncancerous ones. TBARS levels were found to be higher in cancerous tissues than noncancerous ones. In correlation analysis, mostly positive correlations were established between enzyme activities of the cancerous tissues, whereas no meaningful correlations were found between enzyme activities of the noncancerous tissues except for a positive correlation between XO and SOD. The results indicate that the activities of DNA turnover enzymes were reduced, which was possibly an attempt to lower the rate of purine catabolism, and the activities of GSH-Px and CAT enzymes were increased, probably in response to increased free radical stress occurring in cancerous prostate tissues. Increased concentrations of TBARS suggested oxidant stress and thus accelerated peroxidative reactions in the cancerous tissues, even though antioxidant defense mechanisms were activated. These findings suggest that enzymatic antioxidant systems of cancerous prostate tissues cannot sufficiently eliminate oxidant factors and prevent cellular peroxidative reactions occurring during the carcinogenic process.
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PMID:Activities of DNA turnover and free radical metabolizing enzymes in cancerous human prostate tissue. 1037 Mar 68

Extracellular purines are important signalling molecules in the vasculature that are regulated by a network of cell surface ectoenzymes. By using human endothelial cells and normal and leukaemic lymphocytes as enzyme sources, we identified the following purine-converting ectoenzymes: (1) ecto-nucleotidases, NTP diphosphohydrolase/CD39 (EC 3.6.1.5) and ecto-5'-nucleotidase/CD73 (EC 3.1.3.5); (2) ecto-nucleotide kinases, adenylate kinase (EC 2.7.4.3) and nucleoside diphosphate kinase (EC 2.7.4.6); (3) ecto-adenosine deaminase (EC 3.5.4.4). Evidence for this was obtained by using enzyme assays with (3)H-labelled nucleotides and adenosine as substrates, direct evaluation of gamma-phosphate transfer from [gamma-(32)P]ATP to AMP/NDP, and bioluminescent measurement of extracellular ATP synthesis. In addition, incorporation of radioactivity into an approx. 20 kDa surface protein was observed following incubation of Namalwa B cells with [gamma-(32)P]ATP. Thus two opposite, ATP-generating and ATP-consuming, pathways coexist on the cell surface, where basal ATP release, re-synthesis of high-energy phosphoryls, and selective ecto-protein phosphorylation are counteracted by stepwise nucleotide breakdown with subsequent adenosine inactivation. The comparative measurements of enzymic activities indicated the predominance of the nucleotide-inactivating pathway via ecto-nucleotidase reactions on the endothelial cells. The lymphocytes are characterized by counteracting ATP-regenerating/adenosine-eliminating phenotypes, thus allowing them to avoid the lymphotoxic effects of adenosine and maintain surrounding ATP at a steady-state level. These results are in agreement with divergent effects of ATP and adenosine on endothelial function and haemostasis, and provide a novel regulatory mechanism of local agonist availability for nucleotide- or nucleoside-selective receptors within the vasculature.
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PMID:The evidence for two opposite, ATP-generating and ATP-consuming, extracellular pathways on endothelial and lymphoid cells. 1209 90

Enzymes adenosine deaminase (ADA) and 5-nucleotidase (5-'NT) are known to play active role in tissue/cell proliferation and differentiation. To validate this the two enzymes were studied in artificially induced deciduoma of rat and hamster. The deciduoma was induced by traumatizing one of the uterine horns of progesterone primed animals. Non traumatized horn served as control. The animals were later maintained on progesterone, given alone (Gr.I) or conjointly with estrogen (Gr.II). The weight of each uterine horn was recorded to determine the formation of deciduoma. There was no marked difference between the weights of traumatized and control horn on day 2 post-traumatization (PT), but a progressive rise was noticed after this day in both species. The ADA activity however differed, day and species wise. While in the rats of Gr.I it was low in the traumatized horn on all the days, in the hamsters it was remarkably high from day 2 to 6 PT. In the rats of Gr.II also the activity though was low in the traumatized horn, but on day 2 and 4 only; on day 6 and 7 PT it increased markedly. In hamster, on the contrary, again the enzyme activity was remarkably high on all the three days. The 5'-NT activity, however, did not show any marked difference between the two horns under Gr.I and II in both species. It was rather high in the control horn of each group. The results suggest: (I) the progesterone alone though produces a significant rise in the uterine weight of traumatized horn in both species, the ADA activity increases only in hamster, (2) under the conjoint treatment also the enzyme activity remains high in hamster; and (3) the activity of enzyme 5'-NT does not alter during the deciduoma formation in both the species.
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PMID:Expression of adenosine deaminase and 5'-nucleotidase in artificially induced deciduoma in rat and hamster. 1259 17

Membrane vesicles were isolated from rabbit seminal plasma. Electron microscopy analyses showed the presence of numerous small, round vesicles with a diameter of about 70 nm. Determination of enzyme activities was carried out by high performance liquid chromatography and showed that the vesicles can degrade the diadenosine polyphosphates (ApnA), Ap3A and Ap4A and ATP and ADP, but not AMP. Studies of the degradation of diadenosine compounds by the vesicles present in seminal fluid showed an increasing production of AMP as the by-product and a time-dependent generation of dephosphorylated products consistent with the presence of ecto-ATP diphosphophosphatase (ecto-apyrase). In the presence of rabbit spermatozoa, AMP did not accumulate because 5'nucleotidase and adenosine deaminase, present at the surface of sperm cells, transformed AMP into adenosine and inosine. The effects of seminal fluid vesicles and diadenosine compounds on the acquisition of fertilizing capacity by rabbit spermatozoa were evaluated by Pisum sativum agglutinin fluorescein isothiocyanate conjugated staining. The results obtained with uncapacitated spermatozoa showed that the capacitating effector BSA could be substituted efficiently by the addition of diadenosine compounds and vesicles previously incubated for 2 h to the capacitative medium. Under these experimental conditions, the spontaneous acrosome reaction rate was not increased. Capacitated rabbit spermatozoa did not undergo acrosome reaction when l-alpha-lysophosphatidylcholine was substituted by diadenosine compounds previously incubated with vesicles. In conclusion, this study has shown that rabbit seminal fluid vesicles can degrade diadenosine compounds to AMP and that the addition of the vesicles and diadenosine compounds to uncapacitated rabbit spermatozoa favours the acquisition of the fertilizing capacity.
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PMID:Effects of diadenosine polyphosphates and seminal fluid vesicles on rabbit sperm cells. 1277 5

Adenosine is an endogenous hypnotic molecule. However, the mechanism by which the level of extracellular adenosine is regulated remains to be elucidated. We found by Northern hybridization and enzyme assay that ecto-5(')-nucleotidase and adenosine deaminase (ADA), major enzymes responsible for the production and degradation of adenosine, respectively, were localized most abundantly in the leptomeninges within the rat brain. Immunohistochemical study showed that ADA was dominantly localized in arachnoid barrier and trabecular cells of the leptomeninges. In vivo microdialysis demonstrated that externally applied adenosine was rapidly metabolized by ADA to inosine in the subarachnoid space. Perfusion of an ADA inhibitor, coformycin, increased the extracellular adenosine level in the subarachnoid space under the rostral basal forebrain. When coformycin was continuously infused into the subarachnoid space, non-rapid eye movement sleep was increased with prolonged duration of the sleep episode. These results demonstrate that the leptomeninges control the extracellular level of adenosine in the subarachnoid space by their high 5(')-nucleotidase and ADA activities and regulate non-rapid eye movement sleep.
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PMID:Dominant localization of adenosine deaminase in leptomeninges and involvement of the enzyme in sleep. 1463 12

Adenosine is formed during conditions that deplete ATP, such as ischemia. Adenosine deaminase converts adenosine into inosine, and both adenosine and inosine can be beneficial for postischemic recovery. This study investigated adenosine and inosine release from astrocytes and neurons during chemical hypoxia or oxygen-glucose deprivation. In both cell types, 2-deoxyglucose was the most effective stimulus for depleting cellular ATP and for evoking inosine release; in contrast, oxygen-glucose deprivation evoked the greatest adenosine release. alpha,beta-Methylene ADP, an inhibitor of ecto-5'nucleotidase, significantly reduced adenosine release from astrocytes but not neurons. Dipyridamole, an inhibitor of equilibrative nucleoside transporters, inhibited both adenosine and inosine release from neurons. Erythro-9-(2-hydroxy-3-nonyl)adenine, an inhibitor of adenosine deaminase, reduced neuronal inosine release evoked by oxygen-glucose deprivation but not by 2-deoxyglucose treatment. These data indicate that (1). astrocytes release adenine nucleotides that are hydrolyzed extracellularly to adenosine, whereas neurons release adenosine per se, (2). inosine is formed intracellularly and released via nucleoside transporters, and (3). inosine is formed by an adenosine deaminase-dependent pathway during oxygen-glucose deprivation but not during 2-deoxyglucose treatment. In summary, the metabolic pathways for adenosine formation and release were cell-type dependent whereas the pathways for inosine formation were stimulus dependent.
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PMID:Stimulus- and cell-type-specific release of purines in cultured rat forebrain astrocytes and neurons. 1500 86

Blood lymphocyte activities of 5'-nucleotidases, adenosine deaminase and AMP deaminase have been investigated for evaluation of immune system state of albino rats under normal conditions, immobilization stress and effect of radiation. Stress-induced reactions were characterized by changes of activities of these enzymes. However the ratios of activities 5'- nucleotidase/AMP-deaminase (coefficient A) and adenosine-deaminase/AMP-deaminase (coefficient B) were even more informative than separate analysis of these enzymes.
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PMID:[Enzymes of purine nucleotide metabolism in assessment of the functional competence of the immune system]. 1594 54

Multiple sclerosis (MS) is one of the most common causes of neurological disability in young and middle-aged adults and is thought to be mediated by autoreactive T cells. Activities of adenosine deaminase (ADA) and 5'(nucleotidase (5'NT), which are involved in the differentiation and maturation of the lymphoid system, were measured in peripheral blood T cells from 21 MS patients and in 23 age and sex matched healthy controls to determine whether an association existed between these enzyme abnormalities and cellular immune functions. ADA and 5'NT activities were found significantly decreased in MS patients (P < .001 and P < .01 respectively) when compared with controls. Low levels of ADA and 5'NT activities were found irrespective of whether patients had relapsing-remitting or chronic progressive MS. These findings suggest that low levels of these enzyme activities in T cells may be related to the persistent abnormalities in T cell function in the clinical course of MS.
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PMID:Adenosine deaminase and 5'nucleotidase activities in peripheral blood T cells of multiple sclerosis patients. 1607 15


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