Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.5.4.4 (adenosine deaminase)
 5,136 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An in vivo murine model for immunodeficiency of both B and T cells is produced by continuous intraperitoneal infusion of 2'-deoxycoformycin (DCF), a specific tightly binding inhibitor of adenosine deaminase (ADase; adenosine aminohydrolase, EC 3.5.4.4). After DCF infusion, ADase of thymus, spleen, and lymph nodes was inhibited to varying degrees ranging from 57% to 100%. Immunodeficiency under these conditions was indicated by: (i) a striking decrease in lymphocyte response to the T-cell mitogens concanavalin A and phytohemagglutinin; (ii) an impairment of delayed hypersensitivity measured by the footpad reaction; (iii) a decrease in antibody production measured in both in vivo and in vitro plaque-forming cell assay; (iv) a significant prolongation of mouse skin allograft survival after transplantation into the C57BL/6J (H-2b) strain of skin from BALB/c (H-2d) mice; and (v) a marked lymphopenia. Histological examination indicated lymphoid degeneration in the thymus, lymph nodes, and spleen with no alterations in other tissues including bone marrow, kidney, lung, gastrointestinal tract, and liver except for the occurrence of hepatitis. A decrease in the number of Thy-1-positive cells in both spleen and lymph nodes further supported the fact of cytotoxicity of DCF to T cells. Anorexia and weight loss were observed within 5 days of continuous DCF infusion at 0.4 mg/kg body weight per day. These data indicate that this method provides an experimental model for future studies on the biochemical mechanisms responsible for the genetically determined severe combined immunodeficiency disease in man.
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PMID:Animal model for immune dysfunction associated with adenosine deaminase deficiency. 696 8

The purpose of this paper was to study the heterogeneity of human thymocytes and leukemic cells of the T-cell line MOLT-3 by velocity sedimentation. Analysis of the subpopulations of thymocytes demonstrated that they represent a heterogeneous population of cells with respect to their size, proliferative activity, and presence and quantities of terminal deoxynucleotidyl transferase and human thymus leukemia-associated antigen, a thymic isozyme of adenosine deaminase (HThy-L/ADA). Only a minor subpopulation of thymocytes (large cells) was in active cycle. The highest level of HThy-L/ADA was associated with the main subpopulation of thymocytes sedimenting at 3 to 4 mm/hr while low amounts of the HThy-L/ADA antigen (enzyme) were found in the minor fractions of the small and large cells. The distribution of terminal deoxynucleotidyl transferase-positive cells indicated that most, but not all, thymocytes contain the enzyme. Analysis of the T-cell line MOLT-3 showed that these cells could be separated into subpopulations with different biochemical and biological properties. More than one subpopulation of cells was capable of DNA synthesis. In contrast to the thymocytes, all fractions of MOLT-3 cells contained high amounts of HThy-L/ADA. The proportion of terminal deoxynucleotidyl transferase-positive cells as a function of sedimentation velocity was also quite constant although there was a slight but reproducible drop in the percentage of these cells in the slowly sedimenting fractions. The percentage of cells with receptors for sheep erythrocytes also remained high in fractions separated on the basis of size, although a consistently higher percentage was found in smaller cells. These studies indicated that thymus cells as well as the malignant T-cell line MOLT-3 can be separated on the basis of sedimentation velocity into subpopulations with different biological and biochemical properties. The data also indicated that the heterogeneity of MOLT-3 line cannot be explained solely on the basis of volume changes due to cell cycle, suggesting that they may represent heterogeneous populations of cells.
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PMID:Heterogeneity of human thymocytes and a malignant T-lymphoblast cell line, MOLT-3. 697 Nov 48

The effect of continuous infusion into C57BL/6J mice of 2'-deoxycoformycin (DCF), a tight-binding inhibitor of adenosine deaminase, on the biological function of bone marrow stem cells and T- and B-lymphocytes was evaluated. Greater than 85% inhibition of adenosine deaminase in erythrocytes, thymus, and bone marrow was noted after DCF infusion at 0.4 mg per kg body weight per day, while lesser extents of inhibition were characteristic of spleen and lymph nodes. The reconstitution of lethally irradiated C57BL/6J mice with bone marrow cells from DCF- and 0.9% NaCl infused mice of the same strain was compared. The two groups of animals were virtually identical with respect to (a) the number of spleen colony-forming units, (b) the response of splenic lymphocytes to both B- and T-cell mitogens, (c) hematological analysis of peripheral blood elements, and (d) survival time, thus strongly supporting the lack of effect of DCF infusion on the capacity of stem cells to differentiate. In contradistinction, DCF infusion was highly lymphocytotoxic as noted by the severe necrosis in both B- and T-cell regions in lymph nodes and spleen and by the dramatic weight reduction in spleen and thymus. Histopathology of other tissues including bone marrow was normal except for the occurrence of hepatitis. A striking decrease in blastogenesis induced by the mitogens concanavalin A, phytohemagglutinin, and Escherichia coli lipopolysaccharides was also observed after DCF infusion. Consistent with these data, in vitro incubation of bone marrow cells with DCF did not impair the number of spleen colony-forming units produced in lethally irradiated mice. These data suggest a potential use for adenosine deaminase inhibitors in the prevention of graft-versus-host disease in hematopoietic transplantation.
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PMID:Specific immunosuppressive effects of constant infusion of 2'-deoxycoformycin. 697 48

Two fractions of adenosine deaminase (ADA) were separated by ion-exchange chromatography and purified to homogeneity from human thymus tissue by a combination of conventional biochemical methods and affinity chromatography. Some of the physical, chemical and serological properties of the two fractions were compared to those of erythrocyte ADA. All three proteins had apparent molecular weights of about 45,000. They exhibited similar amino acid composition, specific enzymatic activities, Km values for adenosine and antigenic activities as determined by radioimmunoassay. A small portion of ADA isolated from thymus did not bind to complexing protein whereas all of the erythrocyte ADA was bound by this protein. So far, this has been the only difference found between thymic and erythrocyte ADA.
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PMID:Purification and some properties of adenosine deaminase from human thymus. 715 58

The relationship between adenosine deaminase (ADA) and a human membrane thymus leukemia (HTL) antigen-detected by an antithymocyte serum was explored. A freeze-thaw extract of the T-cell-derived cell line, MOLT 4, was applied to an immunoabsorbant column of a rabbit antiserum to calf ADA. The bound MOLT 4 ADA was eluted with 6 M urea. The recovered ADA had a specific activity of 490 mumol of adenosine deaminated per min per mg protein, and the yield was 32%. No HTL antigenic activity was detected in the purified ADA. In addition, no ADA activity was detected in the unbound fraction containing the HTL antigenic activity, supporting the conclusion that ADA and HTL antigen are independent molecules. Affinity-purified anti-calf ADA was not cytotoxic for several HTL antigen-positive cells, including thymocytes, MOLT 4, and thymus-derived acute leukemia lymphoblasts.
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PMID:Relationship between adenosine deaminase and a human thymus leukemia antigen isolated from MOLT 4 cells. 719

We present data on values of adenosine deaminase (ADA) activity in bovine fetus and calf thymus. Between 13 and 17 weeks of fetal life enzyme activity in thymus increases up to levels observed in older fetuses and calf. ADA activity of thymus is characterized by the presence of three enzymic form ("A", "B", "C") which show molecular weights of greater than 1 x 10(6), 310,000 and 55,000, respectively. Forms "B" and "C" were compared. The relative amounts of the three forms in 17 weeks old fetus were quite similar to those observed in calf thymus.
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PMID:[Multiple forms of adenosine deaminase in the thymus of the bovine fetus and calf]. 733 49

Locus control regions (LCRs) are powerful assemblies of cis elements that organize the actions of cell-type-specific trans-acting factors. A 2.3-kb LCR in the human adenosine deaminase (ADA) gene first intron, which controls expression in thymocytes, is composed of a 200-bp enhancer domain and extended flanking sequences that facilitate activation from within chromatin. Prior analyses have demonstrated that the enhancer contains a 28-bp core region and local adjacent augmentative cis elements. We now show that the core contains a single critical c-Myb binding site. In both transiently cotransfected human cells and stable chromatin-integrated yeast cells, c-Myb strongly transactivated reporter constructs that contained polymerized core sequences. c-Myb protein was strongly evident in T lymphoblasts in which the enhancer was active and was localized within discrete nuclear structures. Fetal murine thymus exhibited a striking concordance of endogenous c-myb expression with that of mouse ADA and human ADA LCR-directed transgene expression. Point mutation of the c-Myb site within the intact 2.3-kb LCR severely attenuated enhancer activity in transfections and LCR activity in transgenic thymocytes. Within the context of a complex enhancer and LCR, c-Myb can act as an organizer of thymocyte-specific gene expression via a single binding site.
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PMID:A central role for a single c-Myb binding site in a thymic locus control region. 756 22

Adenosine deaminase (ADA, EC 3.5.4.4) is a ubiquitous enzyme in the purine catabolic pathway. In contrast to the widespread tissue distribution of this enzyme, inherited ADA deficiency in human results in a tissue-specific severe combined immunodeficiency. To explain the molecular basis for this remarkable tissue specificity, we have used a genetic approach to study ADA deficiency. We demonstrate that ADA deficiency causes depletion of CD8low transitional and CD4+CD8+ double-positive thymocytes by an apoptotic mechanism. This effect is mediated by a p53-dependent pathway, since p53-deficient mice are resistant to the apoptosis induced by ADA deficiency. DNA damage, known to be caused by the abnormal accumulation of dATP in ADA deficiency, is therefore responsible for the ablation of T-cell development and for the immunodeficiency. The two thymocyte subsets most susceptible to apoptosis induced by ADA deficiency are also the two thymocyte subsets with the lowest levels of bcl-2 expression. We show that thymocytes from transgenic mice that overexpress bcl-2 in the thymus are rescued from apoptosis induced by ADA deficiency. Thus, the tissue specificity of the pathological effects of ADA deficiency is due to the low bcl-2 expression in CD8low transitional and CD4+CD8+ double-positive thymocytes.
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PMID:p53 expression is required for thymocyte apoptosis induced by adenosine deaminase deficiency. 766 98

We report the generation and characterization of mice lacking adenosine deaminase (ADA). In humans, absence of ADA causes severe combined immunodeficiency. In contrast, ADA-deficient mice die perinatally with marked liver-cell degeneration, but lack abnormalities in the thymus. The ADA substrates, adenosine and deoxyadenosine, are increased in ADA-deficient mice. Adenine deoxyribonucleotides are only modestly elevated, whereas S-adenosylhomocysteine hydrolase activity is reduced more than 85%. Consequently, the ratio of S-adenosylhomocysteine (AdoMet) to S-adenosyl homocysteine (AdoHcy) is reduced threefold in liver. We conclude that ADA plays a more critical role in murine than human fetal development. The murine liver pathology may be due to AdoHcy-mediated inhibition of AdoMet-dependent transmethylation reactions.
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PMID:Adenosine-deaminase-deficient mice die perinatally and exhibit liver-cell degeneration, atelectasis and small intestinal cell death. 767 Apr 65

Deoxycytidine kinase (dCK) phosphorylates 2'-deoxycytidine, as well as the purine deoxyribonucleosides and a number of nucleoside analogues that are important in the chemotherapy of leukemias. The enzyme is highly expressed in the thymus relative to other tissues and may play an important role in the T cell depletion associated with adenosine deaminase and purine nucleoside phosphorylase deficiencies. To characterize the dCK promoter region and to determine whether it mediates higher levels of gene expression in T lymphoblasts, we have analyzed a 700-bp genomic fragment encompassing 548 bp of 5' flanking region for functional activity and for transcription factor binding using T and B lymphoblast cell lines and nuclear extracts. The regions of the promoter that were defined as important to its function include a 5' GC box, and E box, a 3' GC box, and an E2F site. The transcription factor Sp1 binds to both GC boxes, activating at the 5' site but repressing at the 3' site. MLTF/USF activates transcription through the E box, whereas E2F activates through the E2F site, but binds weakly to this site in vitro and does not appear to mediate cell cycle-specific expression of dCK in vivo. No significant differences in promoter activity or transcription factor binding were observed between Jurkat T and Raji B lymphoblasts. The promoter of the dCK gene is thus regulated by a number of ubiquitously expressed transcription factors. DCK expression in cultured lymphoblast cell lines is not solely a function of the T or B lineage derivation.
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PMID:Characterization of the deoxycytidine kinase promoter in human lymphoblast cell lines. 770 74


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