Role Of Adenine Research Articles

Adenine Fine-Tunes DNA Photolyase's Repair Mechanism.

The comparative study of DNA repair by mesophilic and extremophilic photolyases helps us understand the evolution of these enzymes and their role in preserving life on our changing planet. The mechanism of repair of cyclobutane pyrimidine dimer lesions in DNA by electron transfer from the flavin adenine dinucleotide cofactor is the subject of intense interest. The role of adenine in mediating this process remains unresolved. Using microsecond molecular dynamics simulations, we find that adenine mediates the electron transfer in both mesophile and extremophile DNA photolyases through a similar mechanism. In fact, in all photolyases studied, the molecular conformations with the largest electronic couplings between the enzyme cofactor and DNA show the presence of adenine in 10-20% of the strongest-coupling tunneling pathways between the atoms of the electron donor and acceptor. Our theoretical analysis finds that adenine serves the critical role of fine-tuning rather than maximizing the donor-acceptor coupling within the range appropriate for the repair function.

Determinants of Photolyase's DNA Repair Mechanism in Mesophiles and Extremophiles.

Light-driven DNA repair by extremophilic photolyases is of tremendous importance for understanding the early development of life on Earth. The mechanism for flavin adenine dinucleotide repair of DNA lesions is the subject of debate and has been studied mainly in mesophilic species. In particular, the role of adenine in the repair process is poorly understood. Using molecular docking, molecular dynamics simulations, electronic structure calculations, and electron tunneling pathways analysis, we examined adenine's role in DNA repair in four photolyases that thrive at different temperatures. Our results indicate that the contribution of adenine to the electronic coupling between the flavin and the cyclobutane pyrimidine dimer lesion to be repaired is significant in three (one mesophilic and two extremophilic) of the four enzymes studied. Our analysis suggests that thermophilic and hyperthermophilic photolyases have evolved structurally to preserve the functional position (and thus the catalytic function) of adenine at their high temperatures of operation. Water molecules can compete with adenine in establishing the strongest coupling pathway for the electron transfer repair process, but the adenine contribution remains substantial. The present study also reconciles prior seemingly contradictory conclusions on the role of adenine in mesophile electron transfer repair reactions, showing how adenine-mediated superexchange is conformationally gated.

Electron Tunneling Pathways and Role of Adenine in Repair of Cyclobutane Pyrimidine Dimer by DNA Photolyase

Electron Tunneling Pathways and Role of Adenine in Repair of Cyclobutane Pyrimidine Dimer by DNA Photolyase

The Role of Adenine in Fast Excited-State Deactivation of FAD: a Femtosecond Mid-IR Transient Absorption Study

We present a study of excited-state dynamics of two flavin cofactors: flavin-adenine dinucleotide (FAD) and flavin-mononucleotide (FMN). We used femtosecond mid-R transient absorption spectroscopy to study the effect of FAD conformation on its excited-state behavior. The conformation of FAD was modulated by changing the solvent polarity: in D(2)O, FAD is present predominantly in the "stacked" conformation, in which flavin and adenine moieties are in close proximity to each other, whereas the increased amount of DMSO led to an increased amount of the "open" conformer. FMN served as a model system which lacks adenine. We found that the "stacked" conformer undergoes an intramolecular photoinduced electron transfer from adenine to flavin with the forward electron transfer rate of k(f) = 1.9.10(11) s(-1) and the geminate recombination rate of k(b) = 1.1.10(11) s(-1). In the case of the "open" conformer, no intramolecular electron transfer was observed.

W1244 The Role of Adenine and Guanine in Beneficial Effects of the Gastric Pentadecapeptide BPC 157 (PL 14736) On Ileoileal Anastomosis Healing in Rats Impaired with Systemic Corticosteroid Application. Raman Spectroscopy Study

Safe in inflammatory bowel disease (PL14736 Pliva, Croatia), no toxicity reported (Gastroenterology, 2005), gastric pentadecapeptide BPC 157 (BPC 157) heals the intestinal anastomosis (Surg Today, 2007). Raman spectroscopy was used to show the beneficial effect of BPC 157 on anastomosis healing in rats impaired with systemic corticosteroid application. Assessed were Raman spectroscopy, ileoileal anastomosis dehiscence, histology, biomechanical presentation (the volume (ml) (infunded through syringe-perfusion pump system (1ml /10 sec)) and the leakage pressure (mmHg) (catheter connected with chamber and monitor, at 10 cm proximal to anastomosis), on days 1, 2, 3, 4, 5 and 6. BPC 157 10µg, 6-alpha-methylprednisolone (MP) 1 mg, given alone or together /kg i.p. (or an equivolume of saline 5ml/kg). First application was after surgery and last was 24 h before sacrifice. Raman spectroscopy. Measurements used Perkin Elmer Spectrum GX FT Raman spectrometer with 4 cm-1 resolution. Excitation was NdYaG laser at 1064 nm wavelength and used laser power was 500 mW. Spectra were recorded in the area between 300 and 2300 cm-1, with 50 scans for better S/N ratio. Prior to mounting on a universal holder, the specimen was cut to a 0.3 x 0.3 cm piece. Presenting almost constant intensity for all investigated samples, all spectra were baseline corrected and normalized to band at 1450 cm-1. Raman spectroscopy. To point out an advanced healing rate the spectral areas from 510 to 560 cm-1, 800 to 1150 cm-1 and band at 1490 cm-1 were individually observed. We focused the band at 1490 cm-1, assigned to vibrations of adenine and guanine, to be indicative for increased tissue regeneration, since it fully correlates with the evidenced healing process. BPC 157 rats showed an increase throughout the 1-6 days following surgery ; MP-rats did not show before day 6. This healing delay is fully counteracted when rats received BPC 157 simultaneously with MP. Macroscopic and histology data support these findings: adhesion formation attenuated, blood vessels filled, mild passage obstruction only temporary ; anastomosis without leakage sustains markedly higher both volume and pressure, with consistent increase to healthy values ; decreased edema, granulocyte number and necrosis, along with granulation tissue, reticulin and collagen formation substantially increased, and finally epithelization increased (BPC 157) ; (MP)causing aggravation. These data signify the role of adenine and guanine in the anastomosis healing process, BPC 157 has a beneficial effect, MP negative effect, and counteracted corticosteroid impairment by BPC 157 application.

Role of Adenine in Thymine-Dimer Repair by Reduced Flavin-Adenine Dinucleotide

We present a study of excited-state behavior of reduced flavin cofactors using femtosecond optical transient absorption spectroscopy. The reduced flavin cofactors studied were in two protonation states: flavin-adenine dinucleotide (FADH2 and FADH-) and flavin-mononucleotide (FMNH2 and FMNH-). We find that FMNH- exhibits multiexponential decay dynamics due to the presence of two bent conformers of the isoalloxazine ring. FMNH2 exhibits an additional fast deactivation component that is assigned to an iminol tautomer. Reduced flavin cofactors also exhibit a long-lived component that is attributed to the semiquinone and the hydrated electron that are produced in photoinduced electron transfer to the solvent. The presence of adenine in FADH2 and FADH- further changes the excited-state dynamics due to intramolecular electron transfer from the isoalloxazine to the adenine moiety of cofactors. This electron transfer is more pronounced in FADH2 due to pi-stacking interactions between two moieties. We further studied cyclobutane thymine dimer (TT-dimer) repair via FADH- and FMNH- and found that the repair is much more efficient in the case of FADH-. These results suggest that the adenine moiety plays a significant role in the TT-dimer repair dynamics. Two possible explanations for the adenine mediation are presented: (i) a two-step electron transfer process, with the initial electron transfer occurring from flavin to adenine moiety of FADH-, followed by a second electron transfer from adenine to TT-dimer; (ii) the preconcentration of TT-dimer molecules around the flavin cofactor due to the hydrophobic nature of the adenine moiety.

The Metabolism of 14C-adenine and 14C-isopentenyl Pyrophosphate by Soybean Explants, Flowering and Fruiting in vitro

Summary Nodal explants of soybean Glycine max Merrill cv. Impala were grown in vitro and induced to flower and set fruit on a medium containing either 14C-adenine or 14C-isopentenyl pyrophosphate in order to investigate the possibility of these substances being incorporated into cytokinins. Labelled isopentenyl pyrophosphate was incorporated into several substances, none of which had similar chromatographic properties to the authentic cytokinin standards used. Radioactive derivatives of adenine produced after 3 months were concentrated in the flowers. Examination of these radioactive adenine derivatives by HPLC revealed that incorporation was achieved into substances which had similar retention times to those of adenosine, tZ, cZ, DHZR and 2iP. Chemical treatment of some of these peaks was carried out to learn more about their nature. Proof of incorporation of adenine into cytokinins was not conclusive. The possible role of adenine in the flowering of plants is discussed.

The role of adenine in the synthesis of cytokinins in tomato plants and in cell-free root extracts

The incorporation of labelled adenine into cytokinin-like compounds was investigated in intact tomato plants, decapitated tomato roots and cell-free root extracts. In all three cases evidence was found for the incorporation of adenine into endogenous cytokinins. In intact plants and decapitated root systems no evidence was found for the incorporation into cytokinin nucleotides. Cytokinin bases and nucleosides were however, labelled. In the cell-free root extract there was some evidence for the incorporation of labelled adenine into cytokinin nucleotides. This suggests that the biosynthetic process may be strictly compartmentalized. The present results provide no evidence for the relative importance of cytokinin nucleotides in the biosynthetic process. What is clear is that the rate of adenine incorporation into cytokinins is extremely low and that only a small proportion of the cytokinins which became labelled were exported to the shoot via the root exudate.

The Role of Adenine and Adenosine in the Synthesis of Cytokinins by Excised Maize Roots

While cytokinin-like activity was detected in aseptically cultured excised roots of Zea mays no evidence could be found that (8-14C)adenine or (U-14C)adenosine was incorporated into the biologically active compounds over a 42 day culturing period. This information raises serious doubts as to whether adenine and/or adenosine serve as primary precursors for cytokinin biosynthesis. The possibility does however, exist that the excised roots lacked a shoot produced precursor necessary for cytokinin production.

Effect of purines on the formation of the perfect state of Cryptococcus neoformans, Filobasidiella neoformans

A comparative study of growth and mating behaviour of C. neoformans strains grown on nutrient media containing a variety of organic nitrogen sources revealed striking differences of both parameters. Although growth was sparse on an adenine-containing medium, mating was excellent. Attention is drawn to the possible role of adenine in the morphogenesis of F. neoformans.

Purification and characterization of mammalian adenine phosphoribosyltransferases.

In mammals, the enzyme adenine phosphoribosyl transferase (APRT; AMP: pyrophosphate phosphoribosyl transferase; E.C. 2·42·7) is the only known mechanism by which dietary adenine can be utilized1. In humans with reduced or absent APRT activity, renal stones containing substantial amounts of 2,8-dioxyadenine can occur1. However, other APRT deficient individuals do not suffer urolithiasis and appear to be asymptomatic. Thus, the role of APRT, and, indeed, the role of adenine, in the metabolism of mammals is unclear.KeywordsHuman ErythrocyteSyrian HamsterPhosphoribosyl TransferaseElectrophoretic VariantPyrophosphate PhosphoribosylThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Role of adenine and ribose groups of ATP in the heavy meromyosin ATPase reaction.

Role of adenine and ribose groups of ATP in the heavy meromyosin ATPase reaction.

Role of adenine in pathogenesis of Mycoplasma pneumoniae infections of tracheal epithelium.

Adenine sulfate and several related compounds were evaluated for their ability to retard the cytotoxic effect which normally accompanies M. pneumoniae infections of hamster tracheal explants. Adenine sulfate, at the 0.01 mM level, was found to exert a significant protective effect. Little or no ciliostasis or loss of cell viability was detectable when organ cultures were infected with 10(7) CFU of virulent M. pneumoniae in the presence of the adenine supplement. Mycoplasmas grew in broth and on plastic surfaces in the presence of adenine, and no significant diminution of growth rate or cell yield was detectable. Organisms adhered to the tracheal epithelial surface regardless of the presence or absence of adenine. When explants were incubated in the presence of 14C-(8)-adenine, rinsed, and then infected with M. pneumoniae, the adenine label could be recovered from the mycoplasmas 20 h after the infection. These data are compatible with the known nucleic acid requirement of mycoplasmas and with a model which ascribes a role for purine/pyrimidine competition and/or depletion in the infective process.

A specific adenosine phosphorylase, distinct from purine nucleoside phosphorylase

Several enzymes, catalyzing the reversible phosphorolysis of purine nucleosides have been described in eucaryotic cells and in micro-organisms [l-6] . The best known is the ‘purine nucleoside phosphorylase’ (EC 2.4.2.1) acting on the nucleosides of hypoxanthine and guanine. Adenosine is not used as substrate by this enzyme [6-81. Phosphorolysis of adenosine has been reported in Salmonella typhimurium [9], where a single enzyme protein appears to act on inosine, guanosine and adenosine. Adenine was found to be substrate for purine nucleoside phosphorylase of four mammalian sources, but its unfavourable kinetic parameters with respect to those of hypoxanthine and guanine are against the role of adenine as a physiological substrate [lO,l l] . In Mycoplasma both adenosine and inosine phosphorolysis have been observed, but no attempt has been made to correlate the two activities to different proteins [12]. The separation of adenosine phosphorylase from the purine nucleoside phosphorylase has never been reported so far, even though Miech and Coll. have presented indirect evidence that in Schistosoma Mansoni worms adenosine phosphorylase activity is a separate entity from purine nucleoside phosphorylase: this conclusion is based on differences in the pH-activity curves and studies with product and nucleoside analogues inhibitors [ 131. The data presented in this paper give the first direct evidence that at least in B. subtilis the phosphorolysis of adenosine and that of inosine and guanosine are catalyzed by distinct enzyme proteins, which can be

The role of adenine and guanine nucleotides in the activity and response of adenylate cyclase systems to hormones: evidence for multi-site transition states.

The role of adenine and guanine nucleotides in the activity and response of adenylate cyclase systems to hormones: evidence for multi-site transition states.

TRANSIENT EFFECT OF EXOGENOUS ADENINE ON GERMINATION OF ASRERGILLUS ORYZAE CONIDIA

Aspergillus oryzae conidia germinate with good synchrony in a modified Czapek's medium supplemented with L-alanine and adenine. The present report deals with the role of adenine in the process of germination.Exogenous adenine is required only transiently during a period of 40-90 min after inoculation. 14C-Adenine incorporation experiments showed that inosine, AMP, ATP, and NAD comprised nearly 90% of radioactivity in the acid-soluble fraction. Incorporation of 14C-adenine into RNA was accelerated markedly in this transient period. The rate of subsequent protein synthesis was retarded if adenine was not added during the transient period.The present data suggest that the exogenous adenine serves as one of the initiation factors for vegetative growth but not as a trigger for germination.

The role of adenine and adenosine as precursors for adenine nucleotide synthesis by fresh and preserved human erythrocytes

The role of adenine and adenosine as precursors of adenine nucleotides following 12 h incubation was studied with fresh and preserved human erythrocytes. Adenine and glucose double the intracellular ATP level in both fresh and preserved erythrocytes although in the latter in the actual level of ATP after incubation is less due to the initial decrease during preservation at 4°. Adenosine can also elevate the level of ATP to twice that of freshly drawn cells and maintain this level after incubation with preserved blood. The maximum level of ATP obtained with any cells or substrates was twice that of the fresh cells. The incorporation of [8- 14C] adenine or [8- 14C]-adenosine paralleled the increment in ATP levels. When adenine and adenosine were present with fresh cells, both were incorporated into nucleotides at approximately the same rate. As the period of preservation was prolonged the incorporation of [8- 14C]-adenosine was more rapid and accounted for most of the ATP synthesized. The relative ineffectiveness of adenine in preserved blood was due to a decrease in glucose utilization and could be overcome by the use of inosine in the incubation medium. Physiologically aged cells (oldest 5 % of the freshly drawn cells) contained a lower ATP level than that of the rest of the population but this level could also be doubled by incubation with adenine and glucose. The factors which limit the ultimate levels of ATP to twice that found in the fresh cell are discussed. The presence of adenosine kinase in erythrocytes was demonstrated directly by the incorporation of [γ- 32P]ATP into AMP in the presence of adenosine. The enzyme has optimum activity when the molar ratio of ATP: Mg 2+ is 1. Elevated levels of ATP inhibited the kinase, especially at the physiological [Mg 2+] found in the erythrocyte.