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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)

Human adenosine deaminase (ADA; adenosine aminohydrolase, EC 3.5.4.4) was expressed at high levels in cultured mouse cells using a transmissable murine retrovirus vector system. A cDNA clone encoding ADA has been inserted into a plasmid vector containing retroviral transcription and packaging signals as well as a selectable gene for G418 resistance. The constructions were transfected into psi 2 cells, which package the recombinant retroviral genomes into replication-defective virus particles. Isoenzyme analysis for ADA in G418-selected psi 2 cells showed at least 20-fold more human ADA activity than endogenous mouse ADA activity. A mouse T-cell lymphoma line, BL/VL3, was cocultured with transformed psi 2 cells producing human ADA, and some of the cocultured cells were selected for resistance to G418. Both G418-selected and unselected cocultured cells expressed human ADA activity at 25%-50% the level of the endogenous enzyme. Thus, efficient retroviral transduction of ADA expression was obtained.
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PMID:Expression of human adenosine deaminase using a transmissable murine retrovirus vector system. 385 23

Six mouse monoclonal antibodies (mAbs) defining separate systems of cell surface antigens of cultured human renal cancer were tested for reactivity with normal fetal and adult tissues and with neoplastic tissues. Five of the mAbs identified glycoproteins of Mr 160,000 (designated S4), Mr Mr 140,000 (F23), Mr 120,000 (S23 and S27), and Mr 115,000 (S22). The glycoprotein component of Mr 120,000 has been shown recently to be the adenosine deaminase binding protein (ADA-BP) and mAbS23 and mAbS27 define two distinct epitopes on ADA-BP. S22 was not detected on any normal fetal or adult tissues but was found on a subset of renal cancers. S4, F23, S23, and S27 defined distinct domains of the nephron: glomerulus (S4), proximal tubules (S4, F23, S23, and S27), and portions of Henle's loop (S23 and S27). mAbS4 also reacted with the interstitial matrix in the renal medulla and of other tissues, and mAbF23 reacted with fetal and adult fibroblasts. The S23 epitope of ADA-BP was expressed by placental trophoblasts and epithelial cells of breast, prostate, lung, and colon, whereas the S27 epitope was detected on a more limited range of cell types (trophoblasts and prostate epithelium). A panel of 20 renal cell carcinomas was typed for expression of these antigens; 7 phenotypes could be distinguished, with the S4+/F23+/S23+/S27+/S22+ or - phenotype (15 cases) being most common. The other antigenic system, V1, identified a heat-stable antigen that was widely expressed on cultured cell types but showed a restricted pattern of reactivity in tissues. V1 expression was limited to the adrenal cortex, Leydig cells, and the theca of ovarian follicles, and to adrenal cortical carcinomas.
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PMID:Specificity analysis of mouse monoclonal antibodies defining cell surface antigens of human renal cancer. 385 26

The human adenosine deaminase cDNA has been cloned in a lambda-vector. Contained within a sequence of over 1500 nucleotides is an open reading frame of 1089 nucleotides that encodes the amino acids of ADA. The functional ADA gene contains at least six kilobases and has at least two introns. Using in vitro translation, molecular hybridization to ADA cDNA, and S1 nuclease mapping, ADA mRNA has been characterized in lymphoblast lines from seven different ADA-deficient children. All of the lines contain substantial amounts of RNA, which hybridizes specifically to the ADA cDNA. Four of the cell lines contain translatable mRNAs with small defects such as single base substitutions that are not detectable by S1 mapping. Deficiency of ADA activity in these lines appears secondary to synthesis of structurally altered proteins containing simple amino acid substitutions. Three of the lines contain mRNAs with S1 nuclease detectable defects. Some or all of these defective mRNAs are postulated to result from anomalous RNA processing. In these cases the causes of the ADA deficiency may be more complex than simple amino acid substitutions in the protein and could include small insertions or deletions of amino acids as well as changes in the efficiency of translation of the mRNAs.
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PMID:Molecular biology of the adenosine deaminase gene and messenger RNA. 386 73

Cloned cDNA sequences of human adenosine deaminase (ADA; adenosine aminohydrolase, EC 3.5.4.4) have been isolated from a cDNA library constructed in bacteriophage lambda gt10. The cDNA for the library was prepared from poly(A)+ RNA isolated from a human T-lymphoblast cell line, CCRF-CEM. The library was initially screened by differential plaque hybridization to labeled cDNA prepared from human T- and B-lymphoblast cell lines with a 21-fold difference in levels of translatable ADA mRNA. Two recombinants containing cloned cDNA sequences for ADA were identified by hybridization-selected translation. Both recombinants contained approximately 1,600 base pairs of inserted human DNA. Restriction maps of the two inserts were not identical. One contained approximately 40 base pairs of additional DNA toward the center of the cDNA. The cloned cDNA specifically hybridized to five fragments generated by HindIII digestion of human genomic DNA. It also hybridized to human lymphoblast RNA species 1.6 and 5.8 kilobases in length. The cDNA was used as a probe to estimate ADA mRNA levels in human lymphoblast cell lines. ADA mRNA levels correlate closely with levels of ADA catalytic activity and ADA protein in cell lines containing structurally normal ADA. A leukemic T-lymphoblast line produced 6 to 9 times as much ADA protein and ADA mRNA as transformed B-lymphoblast lines. Two mutant B-lymphoblast lines from patients with hereditary ADA deficiency contained unstable ADA protein but had 3 to 4 times the normal level of ADA mRNA.
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PMID:Cloning of cDNA sequences of human adenosine deaminase. 620 Aug 75

Adenosine deaminase (EC 3.5.4.4. - ADA) deaminates adenosine and deoxyadenosine to inosine and deoxyinosine. The distribution of ADA isoenzymes depends on a binding protein. Purine nucleoside phosphorylase (EC 2.4.2.1. - PNP) catabolizes inosine and guanosine to hypoxanthine and guanine. Patients with severe combined immuno-insufficiency often suffer from a congenital ADA deficiency. The PNP deficiency is associated with severely defective T-cell immunity and normal B-cell immunity. Deficiency of ADA leads to an accumulation of adenosine, deoxyadenosine, adenine nucleotides (cAMP, dATP). In PNP deficiency an increased production of inosine, guanosine, deoxyinosine and deoxyguanosine was found. The pathogenesis of the immuno-insufficiency is to be traced back to disturbances in the purine metabolism interfering with the mitogenically induced lymphocyte transformation and other lymphocyte functions, as determined by in vitro tests. Deoxyadenine inhibits the ribonucleoside diphosphate reductase and synthesis of DNA. The overproduction of S-adenosyl-L-homocysteine inhibits methyltransferase reactions and 2'-deoxyadenosine the S-adenosylhomocysteine hydrolase. A decrease of ADA activities was found in T-lymphocytes of patients with Hodgkin's disease. Measurements of ADA activity in patients with leukemias do not explain the impairment of the cellular immune response in leukemias and may be regarded as indicator of increased purine metabolism. The ADA activities are increased in patients with acute immature and chronic myeloic leukemias depending on the activity of the disease. The ADA activity is low in chronic lymphatic leukemia. ADA inhibitors were used for the treatment of T-cell leukemias.
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PMID:[Immune insufficiency in enzyme defects of purine metabolism]. 630 5

Some purine metabolizing enzymes of lymphocytes and granulocytes were determined in 13 patients with cirrhosis of the liver and in a control group consisting of 18 healthy blood donors. Furthermore cytidine deaminase (EC 3, 5, 4, 5) (CRD) activity was determined in the granulocytes of these patients and in 16 controls. An increase of adenosine deaminase (EC 3, 5, 4, 4) (ADA) activity was found in granulocytes (P less than 0.01) as well as in lymphocytes (P less than 0.01) of the cirrhotic patients as compared to controls. Purine nucleoside phosphorylase (EC 2, 4, 2, 1) (PNP) activity in granulocytes and lymphocytes was identical in the two groups. In lymphocytes of cirrhotic patients decreased hypoxanthine guanine phosphoribosyltransferase (EC 2, 4, 2, 8) (HGPRT) (P less than 0.01), adenine phosphoribosyltransferase (EC 2, 4, 2, 7) (APRT) (P less than 0.02) and adenosine kinase activities (EC 2, 7, 1, 20) (AK) (P less than 0.05) were demonstrated. 5'-nucleotidase (5'-N (EC 3, 1, 3, 5) activity in lymphocytes of cirrhotic patients was slightly increased, the increase being correlated to the level of serum gamma globulin. Granulocytes from cirrhotic patients showed a decrease of CRD (P less than 0.05). The finding that ADA activity is increased in mature lymphocytes and granulocytes from cirrhotic patients argues against the possibility that increase of lymphocytes ADA activity is a consequence of malignant transformation or immaturity.
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PMID:Changes in some nucleoside metabolizing enzymes of lymphocytes and granulocytes from patients with cirrhosis of the liver. 641 76

The activity of adenosine deaminase was determined in lymphocytes, erythrocytes and blood plasma of 73 patients with different haematological malignancies and also in healthy control subjects. The enzyme activities were measured using adenosine as substrate and by analysis of released ammonia. Statistically significant decreased enzyme levels in lymphocytes and partial also in erythrocytes were observed in chronic lymphocytic leukaemia, Hodgkin's disease and multiple myeloma. The lower activities of ADA of these patients may be related to the impaired immunological function. In contrast in myeloid leukaemia, blast crisis of myeloid leukaemia and in acute leukaemias significant increased ADA levels in lymphocytes or blast cells were observed. Between the content of blast cells in peripheral blood and ADA activity of the mononuclear cell fraction exists a positive correlation. The increased ADA values of blast cells are a sign of an elevated purine metabolism.
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PMID:[Adenosine deaminase activity in hemoblastoses]. 657 29

Isolation and characterization of 2'-deoxycoformycin from the culture filtrate of the fungus Emericella nidulance is described. Its inhibitory effect on adenosine deaminase (ADA, adenosine aminohydrolase, EC 3.5.4.4) is also described.
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PMID:Production of 2'-deoxycoformycin by the fungus Emericella nidulans and its inhibitory effect on adenosine deaminase. 660 58

JEG-3 is a human choriocarcinoma cell line characterized by low levels of adenosine deaminase expression. For the purpose of studying adenosine deaminase gene regulation in the JEG-3 cells, we attempted to select variant cells having increased adenosine deaminase expression. This was accomplished by selecting cells for resistance to the cytotoxic adenosine analogs 9-beta-D-arabinofuranosyl adenine (ara-A) or 9-beta-D-xylofuranosyl adenine (xyl-A), both of which could presumably be detoxified by the action of adenosine deaminase. Single step high dose selection was ineffective in obtaining cells with increased adenosine deaminase. However, multistep selection using either ara-A or xyl-A resulted in cell populations with increased adenosine deaminase activity. Removal of selective pressure resulted in decreased adenosine deaminase levels. Subclones of xyl-A-resistant cells belonged to one of three phenotypic classes characterized by either elevated adenosine deaminase levels, decreased adenosine kinase levels, or both of these features. One subclone (A3-1A7) with unaltered adenosine kinase expression showed a 20-fold increase in adenosine deaminase expression. Further selection of this subclone for increasing xyl-A resistance resulted in an additional 2-fold increase in adenosine deaminase expression, followed by loss of adenosine kinase expression. These adenosine kinase-deficient cells showed no subsequent increase in adenosine deaminase expression in response to further xyl-A selection pressure. These results confirmed that xyl-A toxicity was mediated through its phosphorylated form and indicated that resistance may result from increased adenosine deaminase levels and/or adenosine kinase deficiency. The increased adenosine deaminase expression of the A3-1A7 subclone was exclusively in the ADA 2 allelic form. However, cell fusion experiments between A3-1A7 cells and mouse C1-1D cells established the existence of functional copies of both ADA 1 and ADA 2 allelic genes in the A3-1A7 cells. The increased expression of only one of the two functional ADA alleles, the requirement for a stepwise selection protocol to obtain cells with increased adenosine deaminase, and the instability of the adenosine deaminase phenotype in the absence of selective pressure suggest that the alteration of adenosine deaminase phenotype in the drug-resistant cells was the result of adenosine deaminase gene amplification.
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PMID:Increased expression of one of two adenosine deaminase alleles in a human choriocarcinoma cell line following selection with adenine nucleosides. 668 74

A commercial preparation of calf adenosine deaminase (calf ADA) was further purified by affinity chromatography and used for immunization of rabbits. The resulting anti-calf-ADA sera reacted by immunodiffusion with both calf and human ADA, and precipitated about 90% of radiolabeled enzyme isolated from human thymus tissue. Moreover, ADA activity was detected in the pellets formed by immunoprecipitation of unlabeled human enzyme by anti-calf-ADA sera. These antisera were successfully used for the immunomorphologic localization of ADA in human thymus tissue and in lymphoid cell preparations. The anti-calf ADA sera could also be used for the immunofluorescent detection of enzyme in rat and mouse thymocytes. The utilization of anti-calf-ADA serum for immunochemical and immunomorphologic detection of enzyme provides a valuable and sensitive reagent for the identification of ADA-positive cells in humans and several other species.
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PMID:Detection of human, rat and mouse adenosine deaminase by immunochemical and immunomorphologic methods using antiserum to calf enzyme. 679 62


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