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)

Several isozymes have been evaluated by other investigators to help characterize both mycoplasmas and acholeplasmas. We have investigated a number of enzymes contributing to hypoxanthine production in Ureaplasma urealyticum, as part of an ongoing effort to identify a comparative profile of isozyme activities in this species. Cells from large volume cultures were collected by centrifugation and lysed by both freeze-thawing and sonication in hypotonic buffer with Triton X-100. Lysate was clarified by centrifugation. Proteins in the cell lysate were separated by polyacrylamide gel electrophoresis, incorporating Triton X-100 in the gel and electrode buffer. Gels were stained to indicate sites of hypoxanthine production from AMP, adenosine, inosine, or adenine, in either phosphate or Tris buffer. The results suggest that adenine deaminase, inosine nucleosidase, and adenosine phosphorylase activities are present in the cell lysate, while adenosine nucleosidase and adenosine deaminase activities are absent. Inosine phosphorylase, AMP nucleosidase and/or 5'-nucleotidase activities may also be present. With the formation of hypoxanthine, the possibility for a salvage pathway exists.
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PMID:Enzyme activities contributing to hypoxanthine production in Ureaplasma. 609

Purine metabolism in Leishmania donovani amastigotes was found to be similar to that of promastigotes with the exception of adenosine metabolism. Adenosine kinase activity in amastigotes is approximately 50-fold greater than in promastigotes. Amastigotes deaminate adenosine to inosine through adenosine deaminase, an enzyme not present in promastigotes. Inosine is cleaved to hypoxanthine and phosphoribosylated by hypoxanthine-guanine phosphoribosyltransferase. Promastigotes cleave adenosine to adenine and deaminate adenine to hypoxanthine via adenase, an enzyme not present in amastigotes. Hypoxanthine is phosphoribosylated by hypoxanthine-guanine phosphoribosyltransferase.
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PMID:Purine metabolism in Leishmania donovani amastigotes and promastigotes. 619 67

The uptake of adenosine by an adenosine kinase deficient variant of C1300 murine neuroblastoma cells has been studied in the absence and in the presence of erythro-9-(2-hydroxy-3-nonyl)adenine, a potent adenine deaminase inhibitor. Although 100 micro M inhibitor completely blocks the metabolism of adenosine under the conditions studied, the uptake of adenosine is concentrative, i.e., the intracellular adenosine concentration exceeds the extracellular concentration. This concentrative effect decreases as the concentration of adenosine increases and is hypothesized to be due to the binding of adenosine to an intracellular component. Despite this concentrative effect, we believe that the kinetics of uptake, as determined in experiments with short (10-20 s) uptake periods, reflect the kinetics of adenosine transport by a facilitated diffusion process. This nucleoside transport system appears to be nonspecific in that the transport of adenosine is competitively antagonized by thymidine. It does not appear to be necessary to inhibit adenosine deaminase in order to study transport in these cells as the Km for transport is not affected by the presence of erythro-9-(2-hydroxy-3-nonyl)adenine. However, erythro-9-(2-hydroxy-3-nonyl)adenine does depress the V for transport. This effect of the inhibitor is probably not due to the inhibition of adenosine deaminase as the transport of thymidine is similarly affected.
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PMID:Adenosine transport by a variant of C1300 murine neuroblastoma cells deficient in adenosine kinase. 624 50

We have previously shown the presence of various purine salvage enzymes in Trypanosoma cruzi, including phosphoribosyltransferase, aminohydrolase, kinase, phosphorylase and hydrolase activities. We now report that a similar situation occurs in Leishmania mexicana amazonensis and Trypanosoma brucei brucei. In all three organisms we found higher levels of activity for the phosphoribosyltransferase enzymes than for the nucleoside kinases, suggesting a preference for the salvage of purine bases rather than nucleosides. Similarly, absence of inosine phosphorylase activity suggests that only one route for the salvage of hypoxanthine is available to the three organisms. The most striking difference was that whereas T. cruzi and T. brucei possessed adenosine aminohydrolase activity, this was not detected in L. mexicana; instead adenine aminohydrolase activity was found. The overall similarity, as judged by the distribution of enzyme activities, of purine salvage in these three members of the kinetoplastida suggest a broad spectrum of activity for any inhibitor acting in this area; the plethora of alternative salvage pathways, however, suggests that in no case would such inhibition be cidal.
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PMID:The enzymes of purine salvage in Trypanosoma cruzi, Trypanosoma brucei and Leishmania mexicana. 631 34

1. Activities of the following enzymes involved in adenine and adenosine metabolism were found in cell-free extracts from Euglena gracilis: acid phosphatase (EC 3.1.3.2), 5'-methylthioadenosine phosphorylase (EC 2.4.2.-), adenine deaminase (EC 3.5.4.2), adenine phosphoribosyltransferase (EC 2.4.2.7) and adenosine kinase (EC 2.7.1.20). 2. The activities occurred both in heterotrophic and photoautotrophic cells and their levels did not change during light-induced chloroplast development. 3. Neither S-adenosylhomocysteinase (EC 3.3.1.1), 5'-methylthioadenosine nucleosidase (EC 3.2.2.9) and nucleoside phosphotransferase (EC 2.7.1.77) nor adenosine degrading enzymes: adenosine deaminase (EC 3.5.4.4), adenosine nucleosidase (EC 3.2.2.7), and purine-nucleoside (adenosine) phosphorylase (EC 2.4.2.1) were found in the Euglena extracts. 4. Comparison of the adenine and adenosine metabolism in Euglena and in other organisms is comprehensively presented. The metabolism in Euglena gracilis differs from that in higher animals and plants.
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PMID:Adenine and adenosine metabolizing enzymes in cell-free extracts from Euglena gracilis. 680 64

Two pathways of adenine utilization are only known in Escherichia coli K-12: the conversion to adenosine monophosphate by adenine phosphoribosyltransferase (apt gene) and ribosylation to adenine nucleosides by purine nucleoside phosphorylase (deoD gene). The purine auxotrophs defective in synthesis of inosine monophosphate de novo (pur) and carrying apt and deoD mutations cannot satisfy their purine requirements by exogenously supplied adenine or adenosine. We have selected spontaneously secondary-site revertants (designated adu) of pur apt deoD mutants, by plating on adenine or adenosine as the sole purine source. The adu mutations frequency was 6-10(-7). The phenotypical suppression of adenine phosphoribosyltransferase and purine nucleoside phosphorylase deficiency by adu mutations is neither the consequence of apt + or deoD + reversions nor the result of appearance in mutant cells of any activity converting adenine to adenosine monophosphate or adenosine. Adenine utilization in adu mutants is not caused by constitutive synthesis or genetic modification of the substrate specificity of adenosine deaminase (add gene). The direct deamination of adenine to give hypoxanthine in extracts of adu2 mutant has been shown. The data obtained suggest the possibility of a new adenine deaminase activity to appear in E. coli by means of single mutations.
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PMID:[Escherichia coli K-12 mutants assimilating adenine via a new metabolic pathway]. 680 33

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

N6-methyladenine (6-methylaminopurine [6-MA]), a plant growth regulator and a normal constituent of nucleic acids, has been found to inhibit the growth of Trypanosoma cruzi, Leishmania braziliensis, L. donovani, L. tarentolae, L. mexicana, and Crithidia fasciculata. The extent of growth inhibition in these organisms is related to the sensitivity of guanine deaminase (guanine aminohydrolase, EC 3.5.4.3), adenine deaminase (adenine aminohydrolase, EC 3.5.4.2), and adenosine hydrolase and phosphorylase. 6-MA was not an inhibitor of the purine phosphoribosyltransferases. Of the trypanosomid flagellates tested. Trypanosoma cruzi was most susceptible to 6-MA. Neither adenine deaminase (as found in the leishmaniae and C. fasciculata) nor adenosine deaminase (as found in mammalian cells) could be demonstrated in T. cruzi. Guanine deaminase, which is strikingly inhibited by 6-MA in T. cruzi, appears to play a major role in the purine salvage pathway of this organism, as judged from growth experiments and enzyme inhibition studies. Enzyme sensitivities to 6-MA vary greatly depending upon the organism. Rabbit liver guanine deaminase was shown to be insensitive to 6-MA at the concentrations used in this study.
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PMID:Inhibition of growth and purine-metabolizing enzymes of trypanosomid flagellates by N6-methyladenine. 699 36

Extracts of Escherichia coli K12 degrade AMP to hypoxanthine, adenine, adenosine, and inosine. Degradation experiments with mutants which lack purine nucleoside phosphorylase or both purine nucleoside phosphorylase and adenosine deaminase demonstrate that hypoxanthine formation is dependent on purine nucleoside phosphorylase. These findings are consistent with an absence of adenine deaminase activity in E. coli. Adenine is formed from AMP in extracts of the E. coli mutants as well as the wild type cells. This activity is due to AMP nucleosidase. Purified, homogeneous AMP nucleosidase gives a subunit Mr = 52,000 on denaturing gel electrophoresis and an oligomer molecular weight of approximately 280,000 by comparative gel filtration. Kinetic studies with this enzyme give cooperative initial rate curves with AMP as substrate, with MgATP2- as an activator, and with Pi as an inhibitor. Phosphate inhibition is competitive with McATP2- (Ki = 0.2 mM) and reverses the activation by MgATP2-. In the absence of MgATP2-, the apparent S0.5 for AMP is 15 mM and decreases to 90 microM at saturating MgATP2-. The maximum rate of AMP hydrolysis is not affected by MgATP2-. Kinetics of MgATP2- activation give a constant for half-maximum activation varying from 120 microM in the presence of low AMP to approximately 2 microM when AMP is present at near saturation. Formycin 5'-PO4 is a powerful competitive inhibitor with respect to AMP, giving a Kis of 72 nM and a Km/Kis ratio of 1,200. Adenylate degradation experiments indicate that AMP nucleosidase is the major enzyme of AMP catabolism in E. coli. The kinetic properties of the purified enzyme indicate that regulation occurs by the intracellular MgATP2- /Pi ratio and the concentration of AMP.
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PMID:Adenylate degradation in Escherichia coli. The role of AMP nucleosidase and properties of the purified enzyme. 700 Jul 83

The adenine analog erythro-9-(2-hydroxy-3-nonyl)adenine, EHNA, a tight reversible inhibitor (KI = 1.6 x 10(-9) M) of adenosine deaminase (EC 3.5.4.4) (ADase), was modified into the fluorescent etheno derivative epsilon-EHNA. The latter is a competitive inhibitor of adenosine deaminase [KI = (2.80 +/- 0.01)10(-6) M], having the fluorescent properties of epsilon-adenines. Affinity to the active site, monitored by both steady-state and dynamic fluorescence polarization, was confirmed by competition experiments with 2'-deoxycoformycin, the substrate adenosine and EHNA. The epsilon-adenine moiety of epsilon-EHNA librates at the shallow active site of ADase. The low absorptivity of epsilon-EHNA required the measurement of fluorescence excitation spectra. Computer subtraction of fluorescence excitation spectrum of ADase from that of its equimolar complex with epsilon-EHNA revealed the corrected excitation spectrum of epsilon-EHNA at the active site of the enzyme. This spectrum mimics that of epsilon-EHNA at pH 5.5 in buffer solution, implying its protonation at the active site of the enzyme. These results are in agreement with the presence of acidic amino acids that are essential to the catalytic mechanism.
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PMID:Probing the active site of adenosine deaminase by a pH responsive fluorescent competitive inhibitor. 947 62


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