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At least 73 records · Page 4Linked to original sources
PubMed1976

[Effect of 2,6-diaminopurine resistance mutations on adenine and adenosine assimilation by cells of an adenine-dependent strain of Escherichia coli K-12].

In purine-requiring strain of Escherichia coli K-12 defective in purine nucleoside phosphorylase (pur, pup) mutants (designated apt) have been obtained that are resistant to 2,6-diaminopurine on guanine-containing medium and incapable to utilize adenine for their growth at 42degreesC, but they are still sensitive to the analogue and can utilize adenine at 28degreesC. It has been shown that the introduction of the corresponding apt mutations in the genome of adenine-requiring strains impaired the ability of these strains to grow on both adenine and adenosine at 42degreesC.

Adenine↗
PubMed1981

[Mathematical modelling of glycolysis and of adenine nucleotide metabolism of human erythrocytes. II. Simulation of adenine nucleotide breakdown following glucose depletion].

The breakdown of adenine nucleotides in human erythrocytes in physiological and alkaline medium at 37 degrees C after glucose depletion is simulated by a mathematical model of energy metabolism. The simulation consists of time dependent solutions of a system of 16 differential equations derived from the stoichiometry of chemical pathways and kinetic properties of enzymes. Starting with the stationary characteristics of the model (M. Schauer et al.: Acta biol. med. germ. 40, 1659, 1981) the results of the simulation were analysed as a function of 1) the share of adenylate deaminase in the degradation of adenine nucleotides and 2) the interaction between adenylate kinase equilibrium and magnesium ions. The experimental data and the simulated concentration changes are in good accord, provided that the assumed activity of adenylate deaminase is very low so that the degradation of adenine nucleotides proceeds mainly via AMP-hydrolysis. The extensive activation of adenylate deaminase during incubation is explained by its sigmoid kinetics with respect to AMP. To improve the results of simulation changes in the adenylate kinase equilibrium have to taken into consideration. These have been measured during incubation of erythrocytes; they can be attributed only partly to the increasing concentration of magnesium ions and to differences among the constants of magnesium association to adenine nucleotides.

Adenine Nucleotides↗
PubMed1987

Interactions of nicotinamide-adenine dinucleotide phosphate analogues and fragments with pigeon liver malic enzyme. Synergistic effect between the nicotinamide and adenine moieties.

The structural requirements of the NADP+ molecule as a coenzyme in the oxidative decarboxylation reaction catalysed by pigeon liver malic enzyme were studied by kinetic and fluorimetric analyses with various NADP+ analogues and fragments. The substrate L-malate had little effect on the nucleotide binding. Etheno-NADP+, 3-acetylpyridine-adenine dinucleotide phosphate, and nicotinamide-hypoxanthine dinucleotide phosphate act as alternative coenzymes for the enzyme. Their kinetic parameters were similar to that of NADP+. Thionicotinamide-adenine dinucleotide phosphate, 3-aminopyridine-adenine dinucleotide phosphate, 5'-adenylyl imidodiphosphate, nicotinamide-adenine dinucleotide 3'-phosphate and NAD+ act as inhibitors for the enzyme. The first two were competitive with respect to NADP+ and non-competitive with respect to L-malate; the other inhibitors were non-competitive with NADP+. All NADP+ fragments were inhibitory to the enzyme, with a wide range of affinity, depending on the presence or absence of a 2'-phosphate group. Compounds with this group bind to the enzyme 2-3 orders of magnitude more tightly than those without this group. Only compounds with this group were competitive inhibitors with respect to NADP+. We conclude that the 2'-phosphate group is crucial for the nucleotide binding of this enzyme, whereas the carboxyamide carbonyl group of the nicotinamide moiety is important for the coenzyme activity. There is a strong synergistic effect between the binding of the nicotinamide and adenosine moieties of the nucleotide molecule.

Adenosine Monophosphate↗
PubMed1985

Severe impairment in adenine metabolism with a partial deficiency of adenine phosphoribosyltransferase.

Among three unrelated patients with recurrent 2,8-dihydroxyadenine urolithiasis, two completely lacked adenine phosphoribosyltransferase (APRT) in both erythrocytes and proliferative T cells. The third patient possessed significant enzyme activities in both hemolysates and T-cell extracts at levels comparable to heterozygotes for complete APRT deficiency. Despite significant APRT activities in cell extracts, cultured T cells from the third patient were at least 100-fold more resistant than normal T cells to an adenine analog, 6-methylpurine, whose cytotoxicity is dependent on APRT. These data indicate that APRT activity in T cells from the third patient is positive in cell extracts, but apparently not operating in viable cells. Although the cells from the patients with complete APRT deficiency were as resistant to 6-methylpurine as the cells from the third patient, the cells from the heterozygotes for complete APRT deficiency were almost as sensitive as normal T cells. Therefore, adenine metabolism in the third patient but not in the heterozygotes seems to be as severely impaired as in the patients with complete APRT deficiency, which is quite consistent with the clinical manifestations in these individuals.

Adenine↗
PubMed1972

Accumulation of adenosine 3':5'-cyclic monophosphate in clonal glial cells: labeling of intracellular adenine nucleotides with radioactive adenine.

The accumulation of endogenous adenosine 3':5'-cyclic phosphate (cAMP) and of [(14)C]cAMP, derived from nucleotides labeled by prior incubation of cells with [(14)C]adenine, has been investigated in four glial cell lines from rats. The following results are similar to data reported for brain slices: (i) rat glial cells contain a system that readily incorporates [(14)C]adenine into nucleotides that serve as precursors for cAMP. (ii) norepinephrine stimulates accumulation of both [(14)C]cAMP and endogenous cAMP, and (iii) the phosphodiesterase inhibitors, papaverine and isobutylmethylxanthine, are effective in enhancing the stimulatory effect of norepinephrine. In contrast to results reported for brain slices, histamine, veratridine, and adenosine, the purine either alone or with a biogenic amine, do not cause an enhanced accumulation of cAMP in rat glial cells, and repetitive accumulations of cAMP can be elicited during a series of restimulations of the cells with norepinephrine. The magnitude of the accumulation of cAMP elicited by the catecholamine decreases markedly by the fifth restimulation in the absence of, but only slightly in the presence of, papaverine. In glial cells, a large portion of the [(14)C]adenine is incorporated into intracellular compounds that do not serve as precursors of [(14)C]cAMP.

Adenine↗
PubMed2006

Highly selective recognition of adenine nucleobases by synthetic hosts with a linked five-six-five-membered triheteroaromatic structure and the application to potentiometric sensing of the adenine nucleotide.

A new structure for an adenine-selective host molecule, featuring the pertinent link of five-six-five-membered heteroaromatic rings and two carbamoyl NH sites, was developed. This structure provides a correctly oriented array of complementary hydrogen bonding sites for the adenine nucleobase, which exploits both Watson-Crick and Hoogsteen-type interactions. The complexation with adenine nucleobases by multiple hydrogen bonding was supported by (1)H NMR spectroscopy. This type of host displayed high selectivity in complexation, with an accompanying fluorescent response to lipophilized adenosine in CHCl(3). Furthermore, a remarkably selective potentiometric response was attained for adenosine 5'-monophosphate over 5'-GMP, 5'-CMP, and 5'-UMP by using an ion-selective electrode with a PVC-supported solvent polymeric membrane. This indicates recognition of water-soluble nucleotide guests through the membrane-water interface. These findings are expected to form a reliable basis for the development of artificial sensing systems for mononucleotides in biological systems.

Adenine↗
PubMed1985

Site-specific immobilization of flavin adenine dinucleotide on indium/tin oxide electrodes through flavin adenine amino group.

A Mannich-type reaction was used to attach flavin adenine dinucleotide (FAD) covalently to aminosilane derivatized indium/tin oxide-coated glass plates. The aminosilane was activated with formaldehyde to give an intermediate that attached specifically to the adenine amino group of FAD. The presence of the intermediate also was demonstrated by coupling hydroquinone to the formaldehyde activated support. The immobilized FAD and hydroquinone were characterized by cyclic or differential pulse voltammetry. The immobilized FAD was shown to reduce the overpotential for NADH oxidation by 180 mV. In keeping with results for FAD on glassy carbon, FAD attached to indium/tin oxide at the adenine amino group did not lead to reconstitution of activity with apoglucose oxidase.

Apoenzymes↗
PubMed1991

Interaction of adenine nucleotides with the adenine nucleotide translocase regulates the developmental changes in proton conductance of the inner mitochondrial membrane.

2-h-old neonatal liver mitochondria, when depleted of adenine nucleotides, showed an 'ohmic' current-voltage relationship and a higher passive proton permeability of the membrane, resembling fetal mitochondrial behaviors for the proton conductance. Incubation of fetal mitochondria with ATP, GDP or carboxyatractyloside promoted a significant reduction in the passive proton permeability of the membrane and the appearance of the characteristic biphasic behavior for the proton conductance. It is concluded that the postnatal increase in intramitochondrial adenine nucleotide concentration promotes, by the interaction of the nucleotides with the adenine nucleotide translocase, the reduction in the passive proton permeability of the mitochondrial membrane, allowing efficient energy conservation in the neonatal liver.

Adenine Nucleotides↗
PubMed1994

Enhanced neoplastic lesion development with adenine-induced experimental multicystic nephropathy by adenine--a model system for the analysis of renal tumor generation in long-term hemodialysis patients.

To cast light on the high incidence of renal cell tumors (RCT) in long-term hemodialysis patients, the role of background multicystic nephropathy was studied in a rat model. Group 1 animals were initially given N-ethyl-N-hydroryethylnitrosamine (EHEN) then subjected to adenine feeding until killing during weeks 20-27. Groups 2 and 3 received EHEN and adenine, respectively. All rats receiving adenine developed multicystic nephropathy. The incidence of renal cell hyperplasias (RCH) and multiplicities of both RCH and RCT in Group 1 were significantly increased as compared with Group 2, suggesting multicystic nephropathy provides favorable environment for tumor development.

Adenine↗
PubMed1982

Detection of separated amino proton resonance signals of adenine derivatives of low temperature and its application to estimation of population of the adenine-uracil dimers in solution.

Splitting of the amino proton signals of 9-ethyladenine derivatives was found in proton nuclear magnetic resonance spectra at low temperature (ca. -30 degrees C). One of the separated signals corresponds to the syn amino proton relative to the N(1) nitrogen in the adenine ring and the other to the anti one. The phenomenon is ascribable to slowing down of the hindered rotation around the N(6)-C(6) bond, which has partial double bond character. On the addition of 1-cyclohexyluracil derivatives, one of the separated signals shifts downfield. From the analysis of the concentration dependence of the signals we could estimate the population of two kinds of adenine-uracil (AU) dimers that employ the syn and anti protons, respectively. i.e. the Watson-Crick-type and the Hoogsteen-type dimers. Independent of the substitution on the uracil ring, the Hoogsteen type is predominant at 70% and the Watson-Crick type at 30% (at -56 degrees C). On the other hand, with mixtures of general kinds of 9-ethyladenine derivatives with 1-cyclohexyluracil. the substituents on the adenine ring cause the population to deviate to extreme values; i.e., either the Watson-Crick-type or the Hoogsteen-type dimer predominates. 2-Chloro-9-ethyladenine and N2-(dimethylamino)-9-ethyladenine take almost completely the Hoogsteen-type dimers, while 8-bromo-9-ethyladenine, N2-(methylamino)-9-ethyladenine, and 2-amino-9-ethylpurine predominant in the Watson-Crick-type dimers.

Adenine↗
PubMed1991

A highly propeller-twisted adenine-adenine base pair in 8-tert-butyladenine.

C9H13N5, Mr = 191.24, monoclinic, P2(1)/c, a = 7.562 (1), b = 6.825 (1), c = 20.905 (1) A, beta = 104.84 (1) degree, V = 1042.9 A3, Z = 4, room temperature, Dx = 1.218 g cm-3, lambda (Cu K alpha) = 1.5418 A, mu = 6.6 cm-1, F(000) = 408. The structure was solved by the multisolution technique and refined by the block-diagonal least-squares method to a final R index of 0.045 using 1970 intensities. The adenine bases form three pairs of hydrogen bonds to symmetry-related molecules in the crystal lattice. Two distinct modes of hydrogen bonding are observed. One mode involves a planar interaction between adjacent adenine bases while the second mode is characterized by an unusually high propeller twist angle of 79.3 degrees between the planes through the two participating adenine bases.

Adenine↗
PubMed1999

Stabilization of the i-motif by intramolecular adenine-adenine-thymine base triple in the structure of d(ACCCT).

The crystal structure of d(ACCCT), solved by molecular replacement, shows a four-stranded i-motif conformation, where two parallel duplexes intercalate with one another in opposite orientations. Each duplex is stabilized by hemi-protonated C-C+ base pairing between parallel strands, and a string of water molecules bridge the cytosine N4 atoms to phosphate O atoms. This structure of d(ACCCT) shows examples of reversed Hoogsteen and Watson-Crick base pairing in both intermolecular and intramolecular manners to stabilize the tetraplex. Noticeably, the four-stranded complex is further stabilized at one end by a three-base hydrogen-bonding network, in which two adenines and a thymine form four hydrogen bonds via a reverse Hoogsteen and an asymmetric adenine-adenine base pairing. The structure of d(ACCCT) shows a similar local structure to that found in the d(TAA) part of the crystal structure of d(TAACCC) and provides further structural evidence that these base arrangements are essential for stabilizing these novel DNA super-secondary structures.

Adenine↗
PubMed1980

Plasma concentration and renal excretion of adenine and 2,8-dihydroxyadenine after administration of adenine in man.

A new method of high performance liquid chromatography (HPLC) which makes it possible to analyse 2,8-dihydroxyadenine (DOA) in plasma in concentrations exceeding 0.25 mumol/l is described. The method was used to study the renal elimination of DOA. For comparison, the renal handling of adenine was also investigated. The results from an analysis of the experimental data support the assumption that more than one concentration-dependent mechanism exists in the renal tubuli for each of the two purines, adenine and DOA. In general the clearance values are higher for DOA than for adenine and indicate net secretion for both substances.

Adenine↗
PubMed1991

5-Phosphoribosyl 1-pyrophosphate synthetase converts the acyclic nucleoside phosphonates 9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine and 9-(2-phosphonylmethoxyethyl)adenine directly to their antivirally active diphosphate derivatives.

The acyclic nucleoside phosphonates 9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (HPMPA) and 9-(2-phosphonylmethoxyethyl)adenine (PMEA) are potent inhibitors of DNA viruses and retroviruses, respectively. Unlike nucleoside triphosphates, the metabolically active (diphosphorylated) forms of HPMPA and PMEA (designated HPMPApp and PMEApp) are synthesized in a reversible reaction in which the pyrophosphate group of 5-phosphoribosyl 1-pyrophosphate (PRPP) is directly transferred to HPMPA and PMEA by purified PRPP synthetase. In this respect, PRPP synthetase does not act stereospecifically in that it recognizes both the S-enantiomer and the R-enantiomer of HPMPA as substrate. PRPP synthetase also recognizes other acyclic adenine and 2,6-diaminopurine riboside phosphonates as a substrate. It is now imperative to evaluate the potential role of PRPP synthetase, as activating enzyme, in the antiviral action of this type of molecules in intact cells.

Adenine↗
PubMed1981

Dual action of high energy adenine nucleotides in comparison with responses evoked by other adenine derivatives and intramural nerve stimulation on smooth muscle.

Fundic strips from stomach smooth muscle of the guinea-pig responded with a contraction preceded by a relatively small relaxation upon addition of the high energy adenine nucleotides ADP and ATP at 37 degree C. The contractile response was concentration-dependent in the range of 10(-8) - 10(-4) M, while the relaxation appeared at higher concentrations (10(-6) - 10(-4) M). The contractile phase observed in the presence of ADP or ATP was inhibited by the prostaglandin antagonist p-benzyl-4-(1-oxo-2-(4-chlorobenzyl)-3-phenylpropyl)phenyl phosphonate (N-0164; 5 X 10(-8) M) The low energy nucleotide AMP, adenosine and the ATP analogue beta, gamma-methyleneadenosine 5'-triphosphate caused relaxation of the stomach muscle. This relaxation was not affected by N-0164 (5 X 10(-8) M). Stimulation of the non-adrenergic inhibitory nerves caused relaxation of the muscle cells, in contrast to the effect of ATP. This seems to be in conflict with the purinergic nerve hypothesis. However, the relaxation evoked by field stimulation may have been due adenosine if it can be assumed that ATP is degraded after its possible release from nerve terminals. Furthermore, the limited availability of ATP if released from nerves for the short period of stimulation is presumably ineffective to stimulate prostaglandin biosynthesis. The results suggest that synthesis of prostaglandins is promoted by the high energy adenine nucleotides ADP and ATP which induce contraction of stomach smooth muscle in contrast with the low energy adenine derivatives and stimulation of the intramural non-adrenergic nerves which produce muscle relaxation.

Adenosine↗
PubMed1977

Responses of adenine nucleotides in germinating soybean embryonic axes to exogenously applied adenine and adenosine.

The ATP content of soybean (Glycine max [L.] Merr. cv. Kent) axes incubated for 3 hours in 1 mm solutions of adenine and adenosine increased over 100% and 75%, respectively, over axes incubated in water. The increase in ATP was primarily due to the conversion of these purines to nucleotides via the nucleotide salvage pathway. The ATP formed was in a metabolically active pool because label from adenine was incorporated into acid-insoluble material. Adenine also increased the levels of GTP, UTP, and CTP, but not to the extent of the ATP level.

Journal Article↗
PubMed1977

Combined antiviral effects of interferon, adenine, arabinoside, hypoxanthine arabinoside, and adenine arabinoside-5'-monophosphate in human fibroblast cultures.

Adenine arabinoside and human interferon are currently being evaluated in clinical trials against herpes- and poxvirus infections. Interferon production is also a normal antiviral response. It is therefore important to examine the combined actions of interferon and antiviral arabinosides for possible synergy or antagonism. We have examined the antiviral activities of human fibroblast interferon, adenine arabinoside, hypoxanthine arabinoside, and adenine arabinoside 5'-monophosphate individually, using plaque inhibition of vaccinia and herpes simplex type 2 viruses in human skin fibroblast cultures. By combining doses of interferon and arabinosides that, acting alone, give intermediate degrees of plaque inhibition, we were able to compare the combined antiviral activity with that calculated from the activity of each inhibitor alone, assuming that the activities are statistically independent. Our results show that the plaque-inhibitory activities of interferon and the arabinosides tested are statistically independent. The results also show that the arabinosides do not destabilize the antiviral state previously induced by interferon, and that interferon pretreatment does not interfere with subsequent arabinoside action in infected cells. We have also found that arabinosides do not affect the induction of interferon synthesis by either Newcastle disease virus or double-stranded ribonucleic acid, and are not themselves interferon inducers.

Antiviral Agents↗