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)

The use of polymers for delivering peptide and protein drugs is described. Soluble-polymer technology attempts to bind a polymer to all sites on therapeutic protein molecules that cause the body to recognize the molecules as foreign. Goals include a stable linkage, water solubility, low immunogenicity, prolonged half-life, and intact biological activity. Polyethylene glycol (PEG)-adenosine deaminase (ADA), or pegademase bovine, has FDA-approved labeling as replacement therapy for ADA deficiency in patients with severe combined immunodeficiency disease who are not suitable candidates for bone marrow transplantation. Pegademase bovine reverses the toxic accumulation of adenosine and deoxyadenosine in adenosine deaminase-deficient cells, restoring the immune system. PEG-asparaginase (pegaspargase) has shown promise in patients with acute lymphocytic leukemia; allergic reactions have been minimal. Animal studies suggest that superoxide dismutase has potential use in conditions in which the body's ability to remove oxygen free radicals is reduced, such as burns and myocardial infarction; coupling with PEG may greatly increase the protein's half-life. Other PEG-conjugated proteins under investigation include PEG-catalase, PEG-uricase, PEG-honeybee venom, PEG-hemoglobin, and PEG-modified ragweed pollen extract. Dextran, albumin, DL-amino acids, and polyvinyl pyrrolidone have also been studied as protein carriers; most of the products created thus far have not shown much promise. The coupling of polymers to proteins has yielded protein drugs with intact biological activity and reduced immunogenicity, but much remains to be learned about this technology.
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PMID:Polymers for delivering peptides and proteins. 816 Jun 72

The hydrolytic activity of calf intestinal adenosine deaminase is reduced sharply, but reversibly, in the presence of added methanol, ethanol, acetonitrile, or dioxane. This decrease in kcat/Km appears to be related to diminished water content in the presence of each of these cosolvents. No agreement between cosolvents is observed if enzyme activity is plotted as a function of viscosity or dielectric constant; nor do these cosolvents act as conventional reversible inhibitors. The Km value of adenosine and the Ki values of a substrate analogue (6-dimethylaminopurine ribonucleoside) and a powerful competitive inhibitor (6-hydroxy-1,6-dihydropurine ribonucleoside) increase with decreasing solvent water content, but kcat is unaffected. Values of 1/Km and 1/Ki increase with roughly the 9th power of the concentration of water and show no sign of approaching a maximum value as the concentration of water approaches 55 M. These results are consistent with an equilibrium between an abundant, inactive, relatively dehydrated form of the enzyme and a rare, relatively hydrated form of the enzyme. Only the hydrated form of the enzyme, containing at least nine more water molecules than the dehydrated form, appears to be capable of binding substrates or competitive inhibitors. Possible physiological consequences of this behavior, in a tissue in which water is transported in large quantities, are considered.
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PMID:Hypersensitivity of an enzyme reaction to solvent water. 836 84

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

Adenosine 5'-monophosphate (AMP) deaminase from baker's yeast is an allosteric enzyme containing a single AMP binding site and two ATP regulatory sites per polypeptide [Merkler, D. J., & Schramm, V. L. (1990) J. Biol Chem. 265, 4420-4426]. The enzyme contains 0.98 +/- 0.17 zinc atom per subunit. The X-ray crystal structure for mouse adenosine deaminase shows zinc in contact with the attacking water nucleophile using purine riboside as a transition-state inhibitor [Wilson, D. K., Rudolph, F. B., & Quiocho, F. A. (1991) Science 252, 1278-1284]. Alignment of the amino acid sequence for yeast AMP deaminase with that for mouse adenosine deaminase demonstrates conservation of the amino acids known from the X-ray crystal structure to bind to the zinc and to a transition-state analogue. On the basis of these similarities, yeast AMP deaminase is also proposed to use a Zn(2+)-activated water molecule to attack C6 of AMP with the displacement of NH3. The pKm and pKi profiles for AMP and a competitive inhibitor overlap in a bell-shaped curve with pKa values of 7.0 and 7.4. This pattern is characteristic of a rapid equilibrium between AMP and the enzyme, thus confirming the rapid equilibrium random kinetic patterns [Merkler, D. J., Wali, A. S., Taylor, J., Schramm, V. L. (1989) J. Biol. Chem. 264, 21422-21430]. The Vmax of the reaction requires one unprotonated and one protonated group with pKa values of 6.4 +/- 0.2 and 7.7 +/- 0.3, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Catalytic mechanism of yeast adenosine 5'-monophosphate deaminase. Zinc content, substrate specificity, pH studies, and solvent isotope effects. 850 99

A typical clinical feature of patients with fasting hyperglycemia in diabetes is well correlated with accelerated hepatic glucose production which is determined by elevated FFA-induced gluconeogenesis. Therefore, to treat fasting hyperglycemia, inhibition of both FFA release and fatty acid oxidation in the liver may be efficient modalities of treatment. (1) Inhibitor of FFA release: a novel selective adenosine A1 agonist, SDZ WAG 994 is a potent inhibitor of adenosine deaminase-induced lipolysis. Twenty-three-week old, male GK rats showing glucose intolerance were treated with WAG 994 (1000 micrograms/kg body weight) for 16 days. Plasma glucose level at 0 time in WAG group was significantly (P < 0.01) less than that of the control. Both plasma FFA and triglyceride concentrations also decreased by 54% and 74%, respectively (vs. control GK rats). (2) Inhibition of hepatic fatty acid oxidation: beta-aminobetaine (emeriamine) is a water-soluble carnitine analog and inhibition of CPT-1 in isolated hepatocytes is 100 times more sensitive than that in isolated cardiocytes and it suppresses both gluconeogenesis and ketogenesis by 60-80%. However, it may be possible that this drug may induce fat deposition in the liver. An inhibitor of elevated fatty acid release from adipose tissue in concomitant with liver-specific and reversible inhibition of fatty acid oxidation may be an effective agent with hypoglycemic and hypolipidemic action for the treatment of diabetes mellitus.
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PMID:Rationale and hurdles of inhibitors of hepatic gluconeogenesis in treatment of diabetes mellitus. 852 14

Molecular dynamics and free energy simulations were performed to examine the binding of (8R)-deoxycoformycin and (8R)-coformycin to adenosine deaminase. The two inhibitors differ only at the 2' position of the sugar ring; the sugar moiety of conformycin is ribose, while it is deoxyribose for deoxycoformycin. The 100 ps molecular dynamics trajectories reveal that Asp 19 and His 17 interact strongly with the 5' hydroxyl group of the sugar moiety of both inhibitors and appear to play an important role in binding the sugar. The 2' and 3' groups of the sugars are near the protein-water interface and can be stabilized by either protein residues or water. The flexibility of the residues at the opening of the active site helps to explain the modest difference in binding of the two inhibitors and how substrates/inhibitors can enter an otherwise inaccessible binding site.
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PMID:Theoretical study of inhibition of adenosine deaminase by (8R)-coformycin and (8R)-deoxycoformycin. 856 17

Adenosine deaminase has been reported to bind the product inosine (the substrate for the reverse reaction) as inosine 1,6-hydrate considered similar in structure to the transition state for adenosine deamination (Wilson & Quiocho, 1994) Accumulation on the enzyme of inosine 1,6-hydrate would be surprising, because this compound is an actual intermediate, probably approaching the transition state, in oxygen exchange between water and the C==O group of inosine, a reaction previously shown to be catalyzed by adenosine deaminase (Wolfenden & Kirsch, 1968). The equilibrium constant for conversion of ES to ES*, in the oxygen exchange reaction, is less than 10-12. To investigate the structure of enzyme-bound inosine in a different way, we labeled deoxyinosine with 13C, excepting an upfield shift of 70-110 ppm if significant rehybridization to sp3 had occurred at the carbonyl group. Instead, the results show a very small shift (1.3 ppm), indicating that C-6 of 2'-deoxyinosine retains its sp2 hybridization after binding by calf intestinal adenosine deaminase. In a separate series of experiments, [4,5-13C]-2'-deoxyuridine was synthesized and found to retain its sp2 hybridization at C-4, after binding by Escherichia coli cytidine deaminase, an enzyme that catalyzes 18O exchange from water into uridine. These findings are consistent with the general expectation, based on the unfavorable equilibrium of activation of enzyme-bound substrates, that enzymes should not accumulate appreciable concentrations of intermediates whose free energies approach that of the transition state in substrate transformation.
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PMID:Enzyme-substrate complexes of adenosine and cytidine deaminases: absence of accumulation of water adducts. 866 59

Two adjacent aspartates, Asp 295 and Asp 296, playing major roles in the reaction catalyzed by mouse adenosine deaminase (mADA) were altered using site-directed mutagenesis. These mutants were expressed and purified from an ADA-deficient bacterial strain and characterized. Circular dichroism spectroscopy shows the mutants to have unperturbed secondary structure. Their zinc content compares well to that of wild-type enzyme. Changing Asp 295 to a glutamate decreases the kcat but does not alter the Km for adenosine, confirming the importance of this residue in the catalytic process and its minimal role in substrate binding. The crystal structure of the D295E mutant reveals a displacement of the catalytic water from the active site due to the longer glutamate side chain, resulting in the mutant's inability to turn over the substrate. In contrast, Asp 296 mutants exhibit markedly increased Km values, establishing this residue's critical role in substrate binding. The Asp 296->Ala mutation causes a 70-fold increase in the Km for adenosine and retains 0.001% of the wild-type kcat/Km value, whereas the ASP 296->Asn mutant has a 10-fold higher Km and retains 1% of the wild-type kcat/Km value. The structure of the D296A mutant shows that the impaired binding of substrate is caused by the loss of a single hydrogen bond between a carboxylate oxygen and N7 of the purine ring. These results and others discussed below are in agreement with the postulated role of the adjacent aspartates in the catalytic mechanism for mADA.
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PMID:Probing the functional role of two conserved active site aspartates in mouse adenosine deaminase. 867 87

Dipeptidyl peptidase IV (DPPIV, EC 3.4.14.5) has been purified 18,000-fold in a yield of 2.2% from human serum. Serum DPPIV, a serine enzyme with an apparent mass of 250 kDa, consists of two identical subunits with an apparent mass of 100 kDa and is inhibited by DPPIV-specific inhibitor Diprotin A and also by p-chloromercuribenzoate (p-CMB), 2-mercaptoethanol, HgCl2, CdCl2, SrCl2, and ZnCl2. One of the remarkable properties of DPPIV is that its activity is greatly enhanced by Gly-X (X: especially, Gly, Gln, Glu and Ser) dipeptides. Gly-X dipeptides increase not only an apparent Km of serum DPPIV for glycyl-L-proline 3,5-dibromo-4-hydroxyanilide nearly 10-fold, but also an apparent kcat nearly 4-fold. This mechanism is unclear, but one possibility is that Gly-Pro from substrate might bind amino acids or dipeptides instead of water molecules as DPPIV transpeptidyl activity reported previously. Another remarkable property of DPPIV is the ability to bind adenosine deaminase-I and -II, as is the case with recombinant soluble CD26 (rsCD26). This probably indicates that DPPIV purified from human serum by our method originates from T-lymphocytes.
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PMID:Human serum dipeptidyl peptidase IV (DPPIV) and its unique properties. 895 16

Crystal structures of the cytidine deaminase-uridine product complex prepared either by cocrystallizing enzyme with uridine or by diffusing cytidine into ligand-free crystals show that the product binds as a 4-ketopyrimidine. They reveal four additional features of the catalytic process. (1) A water molecule bound to a site previously observed to bind the incoming 4-NH2 group represents the site for the leaving ammonia molecule. The conserved Pro 128 accommodates both moieties by orienting the carbonyl group of the previous residue. (2) The Glu 104 carboxylate group rotates from its hydrogen bond to the O4 hydroxyl group in transition-state analog complexes, forming a new hydrogen bond to the leaving group moiety. Thus, after stabilizing the hydroxyl group in the transition state, Glu 104 transfers a proton from that group to the leaving amino group, promoting enol-to-keto isomerization of the product. (3) Difference Fourier comparisons with transition-state complexes indicate that the pyrimidine ring rotates toward the zinc by approximately 10 degrees. The active site thus "pulls" the ring and 4-NH2 group in opposite directions during catalysis. To preserve coplanarity of the 4-keto group with the pyrimidine ring, the N1-C1' glycosidic bond bends by approximately 19 degrees out of the ring plane. This distortion may "spring-load" the product complex and promote dissociation. Failure to recognize a similar distortion could explain an earlier crystallographic interpretation of the adenosine deaminase-inosine complex [Wilson, D. K., & Quiocho, F. A. (1994) Nat. Struct. Biol. 1, 691-694]. (4) The Zn-Sgamma132 bond, which lengthens in transition-state complexes, shortens as the O4 atom returns to a state of lower negative charge in the planar product, consistent with our previous proposal that this bond buffers the zinc bond valence, compensating buildup of negative charge on the oxygen nucleophile during catalysis.
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PMID:The structure of the cytidine deaminase-product complex provides evidence for efficient proton transfer and ground-state destabilization. 912 97


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