The Experts below are selected from a list of 198 Experts worldwide ranked by ideXlab platform
William J. Sullivan - One of the best experts on this subject based on the ideXlab platform.
-
Salvage synthesis of purine Nucleotides by Helicobacter pylori.
Journal of Applied Microbiology, 1994Co-Authors: George L. Mendz, Barbara M. Jiménez, A Margaret C T Gero, Stuart L. Hazell, William J. SullivanAbstract:G.L. MENDZ, B.M. JIMENEZ, S.L. HAZELL, A.M. GERO AND W.J. O'SULLIVAN. 1994. The incorporation of purine nucleotide precursors into Helicobacter pylori and the activities of enzymes involved in nucleotide salvage biosynthetic pathways were investigated by radioactive tracer analysis and nuclear magnetic resonance spectroscopy. The organism took up the nucleobases adenine, guanine and hypoxanthine, and the nucleosides adenosine, guanosine and deoxyadenosine. Any incorporation of deoxyguanosine by the cells was below the detection limits of the methods employed. The activities of adenine-, guanine- and hypoxanthine-phosphoribosyl transferases were established. The bacterium showed high levels of adenosine and guanosine nucleosidase activities and lesser activity for deoxyadenosine; no hydrolysis of deoxyguanosine was detected. Phosphorylase activities were not observed with any of the nucleosides. Phosphotransferase activities with similar rates were demonstrated for adenosine, guanosine and deoxyadenosine; and a weaker activity was detected for deoxyguanosine. No nucleoside kinase activities were observed with any of the nucleosides. The presence of adenylate kinase was established, but no guanylate kinase activity was observed. The study provided evidence for the presence in H. pylori of salvage pathways for the biosynthesis of purine Nucleotides.
-
Salvage synthesis of purine Nucleotides by Helicobacter pylori.
Journal of Applied Microbiology, 1994Co-Authors: George L. Mendz, Barbara M. Jiménez, A Margaret C T Gero, Stuart L. Hazell, William J. SullivanAbstract:G.L. MENDZ, B.M. JIMENEZ, S.L. HAZELL, A.M. GERO AND W.J. O'SULLIVAN. 1994. The incorporation of purine nucleotide precursors into Helicobacter pylori and the activities of enzymes involved in nucleotide salvage biosynthetic pathways were investigated by radioactive tracer analysis and nuclear magnetic resonance spectroscopy. The organism took up the nucleobases adenine, guanine and hypoxanthine, and the nucleosides adenosine, guanosine and deoxyadenosine. Any incorporation of deoxyguanosine by the cells was below the detection limits of the methods employed. The activities of adenine-, guanine- and hypoxanthine-phosphoribosyl transferases were established. The bacterium showed high levels of adenosine and guanosine nucleosidase activities and lesser activity for deoxyadenosine; no hydrolysis of deoxyguanosine was detected. Phosphorylase activities were not observed with any of the nucleosides. Phosphotransferase activities with similar rates were demonstrated for adenosine, guanosine and deoxyadenosine; and a weaker activity was detected for deoxyguanosine. No nucleoside kinase activities were observed with any of the nucleosides. The presence of adenylate kinase was established, but no guanylate kinase activity was observed. The study provided evidence for the presence in H. pylori of salvage pathways for the biosynthesis of purine Nucleotides.
George L. Mendz - One of the best experts on this subject based on the ideXlab platform.
-
purine metabolism and the microaerophily of helicobacter pylori
Archives of Microbiology, 1997Co-Authors: George L. Mendz, Andrew J Shepley, S L Hazell, Mark A SmithAbstract:The requirements for purine nucleotide synthesis, the effects of purine analogues, and the metabolism of adenine in the bacterium Helicobacter pylori were investigated employing cell culture techniques and one-dimensional NMR spectroscopy. Bacterial cells grew and proliferated in media lacking preformed purines, indicating that H. pylori can synthesize purine Nucleotides de novo to meet its requirements. Blocking of this pathway in the absence of sufficient preformed purines for salvage nucleotide synthesis led to cell death. Analogues of purine nucleobases and nucleosides taken up by the cells were cytotoxic, suggesting that salvage routes could be exploited for therapy. Adenine or hypoxanthine were able to substitute for catalase in supporting cell growth and proliferation, suggesting a role for these bases in maintaining the microaerophilic conditions essentially required by the bacterium.
-
Salvage synthesis of purine Nucleotides by Helicobacter pylori.
Journal of Applied Microbiology, 1994Co-Authors: George L. Mendz, Barbara M. Jiménez, A Margaret C T Gero, Stuart L. Hazell, William J. SullivanAbstract:G.L. MENDZ, B.M. JIMENEZ, S.L. HAZELL, A.M. GERO AND W.J. O'SULLIVAN. 1994. The incorporation of purine nucleotide precursors into Helicobacter pylori and the activities of enzymes involved in nucleotide salvage biosynthetic pathways were investigated by radioactive tracer analysis and nuclear magnetic resonance spectroscopy. The organism took up the nucleobases adenine, guanine and hypoxanthine, and the nucleosides adenosine, guanosine and deoxyadenosine. Any incorporation of deoxyguanosine by the cells was below the detection limits of the methods employed. The activities of adenine-, guanine- and hypoxanthine-phosphoribosyl transferases were established. The bacterium showed high levels of adenosine and guanosine nucleosidase activities and lesser activity for deoxyadenosine; no hydrolysis of deoxyguanosine was detected. Phosphorylase activities were not observed with any of the nucleosides. Phosphotransferase activities with similar rates were demonstrated for adenosine, guanosine and deoxyadenosine; and a weaker activity was detected for deoxyguanosine. No nucleoside kinase activities were observed with any of the nucleosides. The presence of adenylate kinase was established, but no guanylate kinase activity was observed. The study provided evidence for the presence in H. pylori of salvage pathways for the biosynthesis of purine Nucleotides.
-
Salvage synthesis of purine Nucleotides by Helicobacter pylori.
Journal of Applied Microbiology, 1994Co-Authors: George L. Mendz, Barbara M. Jiménez, A Margaret C T Gero, Stuart L. Hazell, William J. SullivanAbstract:G.L. MENDZ, B.M. JIMENEZ, S.L. HAZELL, A.M. GERO AND W.J. O'SULLIVAN. 1994. The incorporation of purine nucleotide precursors into Helicobacter pylori and the activities of enzymes involved in nucleotide salvage biosynthetic pathways were investigated by radioactive tracer analysis and nuclear magnetic resonance spectroscopy. The organism took up the nucleobases adenine, guanine and hypoxanthine, and the nucleosides adenosine, guanosine and deoxyadenosine. Any incorporation of deoxyguanosine by the cells was below the detection limits of the methods employed. The activities of adenine-, guanine- and hypoxanthine-phosphoribosyl transferases were established. The bacterium showed high levels of adenosine and guanosine nucleosidase activities and lesser activity for deoxyadenosine; no hydrolysis of deoxyguanosine was detected. Phosphorylase activities were not observed with any of the nucleosides. Phosphotransferase activities with similar rates were demonstrated for adenosine, guanosine and deoxyadenosine; and a weaker activity was detected for deoxyguanosine. No nucleoside kinase activities were observed with any of the nucleosides. The presence of adenylate kinase was established, but no guanylate kinase activity was observed. The study provided evidence for the presence in H. pylori of salvage pathways for the biosynthesis of purine Nucleotides.
Torsten Mohlmann - One of the best experts on this subject based on the ideXlab platform.
-
nucleobase and nucleoside transport and integration into plant metabolism
Frontiers in Plant Science, 2014Co-Authors: Christopher Girke, Manuel Daumann, Sandra Niopekwitz, Torsten MohlmannAbstract:Nucleotide metabolism is an essential process in all living organisms. Besides newly synthesized Nucleotides, the recycling (salvage) of partially degraded Nucleotides, i.e., nucleosides and nucleobases serves to keep the homeostasis of the nucleotide pool. Both types of metabolites are substrates of at least six families of transport proteins in Arabidopsis thaliana (Arabidopsis) with a total of 49 members. In the last years several members of such transport proteins have been analyzed allowing to present a more detailed picture of nucleoside and nucleobase transport and the physiological function of these processes. Besides functioning in nucleotide metabolism it turned out that individual members of the before named transporters exhibit the capacity to transport a wide range of different substrates including vitamins and phytohormones. The aim of this review is to summarize the current knowledge on nucleobase and nucleoside transport processes in plants and integrate this into nucleotide metabolism in general. Thereby, we will focus on those proteins which have been characterized at the biochemical level.
-
nucleoside transport and associated metabolism
Plant Biology, 2010Co-Authors: Torsten Mohlmann, Sylvia Hach, C Bernard, Ekkehard H NeuhausAbstract:: Nucleosides are intermediates of nucleotide metabolism. Nucleotide de novo synthesis generates the nucleoside monophosphates AMP and UMP, which are further processed to all purine and pyrimidine Nucleotides involved in multiple cellular reactions, including the synthesis of nucleic acids. Catabolism of these substances results in the formation of nucleosides, which are further degraded by nucleoside hydrolase to nucleobases. Both nucleosides and nucleobases can be exchanged between cells and tissues through multiple isoforms of corresponding transport proteins. After uptake into a cell, nucleosides and nucleobases can undergo salvage reactions or catabolism. Whereas energy is preserved by salvage pathway reactions, catabolism liberates ammonia, which is then incorporated into amino acids. Keeping the balance between nitrogen consumption during nucleotide de novo synthesis and ammonia liberation by nucleotide catabolism is essential for correct plant development. Senescence and seed germination represent situations in plant development where marked fluctuations in nucleotide pools occur. Furthermore, extracellular nucleotide metabolism has become an immensely interesting research topic. In addition, selected aspects of nucleoside transport in yeast, protists and humans are discussed.
Nicholas V Hud - One of the best experts on this subject based on the ideXlab platform.
-
Prebiotic Syntheses of Noncanonical Nucleosides and Nucleotides.
Chemical reviews, 2020Co-Authors: David M Fialho, Tyler P. Roche, Nicholas V HudAbstract:The origin of Nucleotides is a major question in origins-of-life research. Given the central importance of RNA in biology and the influential RNA World hypothesis, a great deal of this research has focused on finding possible prebiotic syntheses of the four canonical Nucleotides of coding RNA. However, the use of Nucleotides in other roles across the tree of life might be evidence that Nucleotides have been used in noncoding roles for even longer than RNA has been used as a genetic polymer. Likewise, it is possible that early life utilized Nucleotides other than the extant Nucleotides as the monomers of informational polymers. Therefore, finding plausible prebiotic syntheses of potentially ancestral noncanonical Nucleotides may be of great importance for understanding the origins and early evolution of life. Experimental investigations into abiotic noncanonical nucleotide synthesis reveal that many noncanonical Nucleotides and related glycosides are formed much more easily than the canonical Nucleotides. An analysis of the mechanisms by which nucleosides and Nucleotides form in the solution phase or in drying-heating reactions from pre-existing sugars and heterocycles suggests that a wide variety of noncanonical Nucleotides and related glycosides would have been present on the prebiotic Earth, if any such molecules were present.
-
spontaneous formation and base pairing of plausible prebiotic Nucleotides in water
Nature Communications, 2016Co-Authors: Brian J Cafferty, David M Fialho, Jaheda Khanam, Ramanarayanan Krishnamurthy, Nicholas V HudAbstract:The RNA World hypothesis presupposes that abiotic reactions originally produced Nucleotides, the monomers of RNA and universal constituents of metabolism. However, compatible prebiotic reactions for the synthesis of complementary (that is, base pairing) Nucleotides and mechanisms for their mutual selection within a complex chemical environment have not been reported. Here we show that two plausible prebiotic heterocycles, melamine and barbituric acid, form glycosidic linkages with ribose and ribose-5-phosphate in water to produce nucleosides and Nucleotides in good yields. Even without purification, these Nucleotides base pair in aqueous solution to create linear supramolecular assemblies containing thousands of ordered Nucleotides. Nucleotide anomerization and supramolecular assemblies favour the biologically relevant β-anomer form of these riboNucleotides, revealing abiotic mechanisms by which nucleotide structure and configuration could have been originally favoured. These findings indicate that nucleotide formation and selection may have been robust processes on the prebiotic Earth, if other nucleobases preceded those of extant life.
J Olivares - One of the best experts on this subject based on the ideXlab platform.
-
Basis of Pyrimidine Nucleotide Metabolism in the Myocardium
Cardiovascular Drugs and Therapy, 1998Co-Authors: André Rossi, J OlivaresAbstract:The metabolism of pyrimidine Nucleotides in the myocardium is poorly understood. The turnover of these Nucleotides is high, whereas their concentration is rather low. The de novo pathway of synthesis does not seem very efficient, although the utilization of nucleosides could represent the major pathway for pyrimidine nucleotide synthesis. In rat blood, cytidine could be the major precursor for pyrimidine nucleotide synthesis. The precursor, whatever its exact nature (uridine or cytidine), could be species dependent, and the liver could play a major role in providing blood nucleosides. Owing to the essential role of pyrimidine Nucleotides in the synthesis of macromolecules, acute or chronic alteration of the metabolism of these Nucleotides could have crucial consequences on heart viability and function. Providing pyrimidine precursors to the heart, isolated or in situ, induces functional and metabolic effects on the heart. The experimental results suggest that such interventions could be beneficial in clinical situations such as cardioplegia, heart preservation, or recovery from ischemia.