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)

A number of infants with an autosomal recessive form of combined immunodeficiency disease also lack adenosine deaminase (adenosine aminohydrolase; EC 3.5.4.4) activity in their erythrocytes. Other tissues from these infants contain only a few percent of the adenosine-deaminating activity present in corresponding normal tissue. The residual adenosine-deaminating activity in extracts from the spleen of a combined immunodeficient, adenosine deaminase-deficient patient was compared with adenosine deaminase from normal spleen. Affinity and immunoadsorbant column chromatography revealed distinct differences between the adenosine-deaminating activity in the patient's spleen and adenosine deaminase from normal spleen. The point of maximum activity and general configuration of the pH optimum curves were also different. erythro-9-(2-Hydroxyl-3-nonyl)adenine, a potent inhibitor of adenosine deaminase from normal spleen, had relatively little effect on the activity from the patient's spleen. In contrast, adenine was a better inhibitor of the activity in the patient's spleen than it was of the enzyme from normal tissue. An adenosine-deaminating activity with the same characteristics and specific activity as that in the patient's spleen was also isolated from normal spleen. These results suggest that the adenosine-deaminating activity in the spleen of this patient is not due to a mutant form of adenosine deaminase.
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PMID:Characterization of the residual adenosine deaminating activity in the spleen of a patient with combined immunodeficiency disease and adenosine deaminase deficiency. 2 16

Adenosine deaminase was purified 3038-fold to apparent homogeneity from human leukaemic granulocytes by adenosine affinity chromatography. The purified enzyme has a specific activity of 486 mumol/min per mg of protein at 35 degrees C. It exhibits a single band when subjected to sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, non-denaturing polyacrylamide-gel electrophoresis and isoelectric focusing. The pI is 4.4. The enzyme is a monomeric protein of molecular weight 44000. Both electrophoretic behaviour and molecular weight differ from those of the low-molecular-weight adenosine deaminase purified from human erythrocytes. Its amino acid composition is reported. Tests with periodic acid-Schiff reagent for associated carbohydrate are negative. Of the large group of physiological compounds tested as potential effectors, none has a significant effect. The enzyme is specific for adenosine and deoxyadenosine, with Km values of 48 microM and 34 microM respectively. There are no significant differences in enzyme function on the two substrates. erythro-9-(2-Hydroxy non-3-yl) adenine is a competitive inhibitor, with Ki 15 nM. Deoxycoformycin inhibits deamination of both adenosine and deoxyadenosine, with an apparent Ki of 60-90 pM. A specific antibody was developed against the purified enzyme, and a sensitive radioimmunoassay for adenosine deaminase protein is described.
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PMID:Purification, characterization and radioimmunoassay of adenosine deaminase from human leukaemic granulocytes. 694 96

Formation of tetrahedral transition intermediates is a key step in many enzyme catalyzed reactions. Much of our understanding of these and other intermediates, at the atomic level, has come from crystallographic studies of very few enzymes with bound, synthetic, transition-state analogues. Here we present the structure of adenosine deaminase, a zinc-metalloenzyme critical in both purine metabolism and development of the lymphoid system, having performed a stereospecific hydroxide addition to the C6 of inosine. This addition causes the O6 oxygen of inosine to assume an orientation analogous to the position of the amino leaving group of the tetrahedral intermediate in the enzyme-catalyzed hydrolytic deamination of adenosine to inosine.
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PMID:Crystallographic observation of a trapped tetrahedral intermediate in a metalloenzyme. 763 72

The crystal structure of urease from Klebsiella aerogenes has been determined at 2.2 A resolution and refined to an R factor of 18.2 percent. The enzyme contains four structural domains: three with novel folds playing structural roles, and an (alpha beta)8 barrel domain, which contains the bi-nickel center. The two active site nickels are 3.5 A apart. One nickel ion is coordinated by three ligands (with low occupancy of a fourth ligand) and the second is coordinated by five ligands. A carbamylated lysine provides an oxygen ligand to each nickel, explaining why carbon dioxide is required for the activation of urease apoenzyme. The structure is compatible with a catalytic mechanism whereby urea ligates Ni-1 to complete its tetrahedral coordination and a hydroxide ligand of Ni-2 attacks the carbonyl carbon. A surprisingly high structural similarity between the urease catalytic domain and that of the zinc-dependent adenosine deaminase reveals a remarkable example of active site divergence.
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PMID:The crystal structure of urease from Klebsiella aerogenes. 775 94

The synthesis and biological evaluation of three chain-hydroxylated (+)-erythro-9-(2S-hydroxy-3R-nonyl)adenine [(+)-EHNA] derivatives are reported. Hydroxy groups at positions 9', 8', and 8',9' (12, 25, and 16) were introduced by either epoxidation or hydroboration of a terminal olefinic intermediate. Affinities for calf intestinal adenosine deaminase (ADA) were determined from the steady-state inhibition of adenosine deamination. Ki values of 0.82, 3.8, 6.4, and 15.8 nM were estimated for (+)-EHNA, 9'-hydroxy-(+)-EHNA (12), 8'-hydroxy-(+)-EHNA (25), and 8',9'-dihydroxy-(+)-EHNA (16), respectively, by assuming a single class of binding sites. However, the data for all inhibitors conformed more closely to the kinetics of a heterogeneous system with different affinities for two or more binding sites. The fairly high potencies of 12 and 25 suggest that other substitutions at the terminal position of the nonyl chain could yield useful ADA inhibitors.
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PMID:Adenosine deaminase inhibitors. Synthesis and biological evaluation of putative metabolites of (+)-erythro-9-(2S-hydroxy-3R-nonyl)adenine. 796 42

We have solved the structure of Escherichia coli cytidine deaminase (CDA) complexed to the transition state analog, 5-fluoroprimidin-2-one riboside. The monomer of the alpha 2 CDA dimer is composed of a small N-terminal alpha-helical domain with no obvious connection to the active sites, and two, larger, core domains. The two core domains have nearly identical tertiary structures and are related by approximate 2-fold symmetry, but lack internal amino acid sequence homology. Comparison of the core domain structure with known structures by sequence homology and structural compatibility searches suggests that the CDA tertiary structure cannot be superimposed on any known protein structure. The two active sites per dimer are formed across the subunit interface. The N-terminal core domain provides a pyrimidine nucleoside and zinc-binding pocket and the structurally homologous C-terminal core domain in the other monomer covers this active-site cleft, completely sequestering the ligand from solvent. The deeply buried zinc-binding site is formed by a novel "topological switch point" at the amino termini of two alpha-helices in consecutive alpha-beta-alpha-beta segments. The transition state analog is bound as a covalent hydrate at C4. The inhibitor hydroxyl oxygen atom interacts both with the zinc atom and the Glu104 carboxylate group, affording high differential affinity for the hydroxyl group relative to a hydrogen atom, in a manner reminiscent of that observed in adenosine deaminase (ADA). Unlike the latter enzyme, the zinc atom is coordinated in a tetrahedral ligand field to two cysteine and one histidine ligands, plus the hydroxyl group. Moreover, the inhibitor stereochemistry is of the opposite hand from that of the corresponding ADA inhibitor at C4(R), but is the same at the hydroxyl group O4(S). A consequence of these stereochemical differences is that in CDA a single conserved carboxylate side-chain, Glu104, can provide all of the necessary proton transfer functions involved in generating the zinc hydroxide nucleophile, and protonating the pyrimidine ring nitrogen atom and leaving amino group. The differences in zinc ligands, ligand-binding stereochemistry, and tertiary structures of CDA and ADA strongly suggest that the common features of transition state stabilization arose by convergent evolution.
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PMID:Cytidine deaminase. The 2.3 A crystal structure of an enzyme: transition-state analog complex. 828 86

The refined 2.4-A structure of adenosine deaminase, recently discovered to be a zinc metalloenzyme [Wilson, D. K., Rudolph, F. B., & Quiocho, F. A. (1991) Science 252, 1278-1284], complexed with the ground-state analog 1-deazaadenosine shows the mode of binding of the analog and, unexpectedly, a zinc-activated water (hydroxide). This structure of a pre-transition-state mimic, combined with that previously determined for the complex with 6(R)-hydroxy-1,6-dihydropurine ribonucleoside, a nearly ideal transition-state analog, sheds new understanding of the precise stereospecificity and hydrolytic catalysis of an important and well-characterized member of a large group of zinc metalloenzymes. As both of these excellent mimics were generated in the active site, they demonstrate a powerful means of dissecting the course of an enzymatic reaction by direct crystallographic analysis.
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PMID:A pre-transition-state mimic of an enzyme: X-ray structure of adenosine deaminase with bound 1-deazaadenosine and zinc-activated water. 843 34

We previously reported that adenosine A1 receptor activation protects against the cardiodepressant effects of hydrogen peroxide in isolated rat hearts. The present study examined whether a transient ischemic period of 5 min duration, which preconditions the heart against ischemic and reperfusion-induced dysfunction, can bestow protection against 30-min exposure to hydrogen peroxide in isolated rat hearts. Transient ischemia on its own failed to alter the cardiac response to hydrogen peroxide. However, when transient ischemia was carried out in the presence of the nucleoside transport inhibitor S-(4-Nitrobenzyl)-6-thioguanosine and the adenosine deaminase inhibitor erythro-9-(2-Hydroxy-3-nonyl)adenine, a significant attenuation of the hydrogen peroxide-induced loss in contractility was evident and this was associated with significant preservation of tissue glycogen content. The protective effect of the transient ischemia/drug combination on both functional changes and glycogen levels was abolished by the adenosine A1 receptor antagonist 8-cyclopentyl-1, 3-dipropylxanthine as well as by glibenclamide, a blocker of the ATP-sensitive potassium channel (KATP). To further assess the role of glycogen in the protection against hydrogen peroxide, we compared the effects of the adenosine A1 agonist N6-cyclopentyl adenosine (CPA) and insulin. While both treatments protected against hydrogen peroxide the effect of insulin was superior to any other treatment. Moreover, while all protective modalities preserved glycogen stores after hydrogen peroxide treatment, the protection afforded by insulin was also associated with significantly elevated glycogen levels prior to hydrogen peroxide administration. No protection by either CPA or insulin was evident in the absence of exogenous glucose. Taken together, our results demonstrate that a brief period of ischemia with concomitant administration of agents which increase interstitial adenosine levels protects against hydrogen peroxide toxicity. The effect is mediated by activation of adenosine A1 receptors and is linked to KATP stimulation. Moreover, our results are strongly suggestive of an important role of glycogen preservation in bestowing protective effects against hydrogen peroxide cardiotoxicity.
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PMID:Transient ischemia in the presence of an adenosine deaminase plus a nucleoside transport inhibitor confers protection against contractile depression produced by hydrogen peroxide. Possible role of glycogen. 876 52

Heavy atom isotope effects are a valuable tool for probing chemical and enzymatic reaction mechanisms; yet, they are not widely applied to examine mechanisms of nucleophilic activation. We developed approaches for analyzing solvent (18)O nucleophile isotope effects ((18)k(nuc)) that allow, for the first time, their application to hydrolysis reactions of nucleotides and nucleic acids. Here, we report (18)k(nuc) for phosphodiester hydrolysis catalyzed by Mg(2+) and by the Mg(2+)-dependent RNase P ribozyme and deamination by the Zn(2+)-dependent protein enzyme adenosine deaminase (ADA). Because ADA incorporates a single solvent molecule into the product inosine, this reaction can be used to monitor solvent (18)O/(16)O ratios in complex reaction mixtures. This approach, combined with new methods for analysis of isotope ratios of nucleotide phosphates by whole molecule mass spectrometry, permitted determination of (18)k(nuc) for hydrolysis of thymidine 5'-p-nitrophenyl phosphate and RNA cleavage by the RNase P ribozyme. For ADA, an inverse (18)k(nuc) of 0.986 +/- 0.001 is observed, reflecting coordination of the nucleophile by an active site Zn(2+) ion and a stepwise mechanism. In contrast, the observed (18)k(nuc) for phosphodiester reactions were normal: 1.027 +/- 0.013 and 1.030 +/- 0.012 for the Mg(2+)- and ribozyme-catalyzed reactions, respectively. Such normal effects indicate that nucleophilic attack occurs in the rate-limiting step for these reactions, consistent with concerted mechanisms. However, these magnitudes are significantly less than the (18)k(nuc) observed for nucleophilic attack by hydroxide (1.068 +/- 0.007), indicating a "stiffer" bonding environment for the nucleophile in the transition state. Kinetic analysis of the Mg(2+)-catalyzed reaction indicates that a Mg(2+)-hydroxide complex is the catalytic species; thus, the lower (18)k(nuc), in large part, reflects direct metal ion coordination of the nucleophilic oxygen. A similar value for the RNase P ribozyme catalyzed reaction provides support for nucleophilic activation by metal ion catalysis.
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PMID:Analysis of solvent nucleophile isotope effects: evidence for concerted mechanisms and nucleophilic activation by metal coordination in nonenzymatic and ribozyme-catalyzed phosphodiester hydrolysis. 1530 52