Relevant bibliographies by topics / Purine catabolism

Academic literature on the topic 'Purine catabolism'

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Published: 10 December 2022
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Journal articles on the topic "Purine catabolism"

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Tomlinson, Patricia Tolson, and Carol J. Lovatt. "Nucleotide Metabolism in ‘Washington’ Navel Orange Fruit: I. Pathways of Synthesis and Catabolism." Journal of the American Society for Horticultural Science 112, no. 3 (May 1987): 529–35. http://dx.doi.org/10.21273/jashs.112.3.529.

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Abstract The capacity of ‘Washington’ navel orange fruit [Citrus sinensis (L.) Osbeck] to synthesize and catabolize purines and pyrimidines was assessed. De novo biosynthesis of purine nucleotide was demonstrated by [14C] bicarbonate incorporation into purine nucleotides, blockage of this process by four known inhibitors, and assimilation of radiolabeled carbon from formate, both carbons of glycine, and carbon-3 of serine into the adenine ring. De novo synthesis of pyrimidines via the orotate pathway in young fruit was demonstrated by incorporation of [14C] bicarbonate and [6-14C]orotic acid into uridine nucleotides, release of 14CO2 from [7-14C]orotic acid, and blockage of these processes by 6-azauridine. Synthesis of purine and pyrimidine nucleotides via salvage reactions was demonstrated by incorporation of radiolabeled bases and ribonucleosides into nucleotides and into nucleic acids. Release of 14CO2 from radiolabeled adenine, adenosine, hypoxanthine, and xanthine, uric acid, urea (purines), uracil, and uridine (pyrimidines) provided evidence the pathways for catabolism (degradation) of purines and pyrimidines in navel orange fruit are similar to those found in microorganisms and animal tissues. To the best of our knowledge, this report is the first to assess the capacity of anabolic and catabolic pathways of purine and pyrimidine nucleotide metabolism in fruit of any species. De novo synthetic activities in orange fruit permit increases in the pools of purine and pyrimidine nucleotides using simple precursors. Further, the patterns of salvage and catabolism suggest riboside pools are reused predominantly as nucleotides, while the majority of base pools are degraded to permit recycling of carbon and nitrogen into other metabolites.
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Xi, Hualin, Barbara L. Schneider, and Larry Reitzer. "Purine Catabolism in Escherichia coliand Function of Xanthine Dehydrogenase in Purine Salvage." Journal of Bacteriology 182, no. 19 (October 1, 2000): 5332–41. http://dx.doi.org/10.1128/jb.182.19.5332-5341.2000.

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ABSTRACT Escherichia coli is not known to utilize purines, other than adenine and adenosine, as nitrogen sources. We reinvestigated purine catabolism because a computer analysis suggested several potential ς54-dependent promoters within a 23-gene cluster whose products have homology to purine catabolic enzymes. Our results did not provide conclusive evidence that the ς54-dependent promoters are active. Nonetheless, our results suggest that some of the genes are metabolically significant. We found that even though several purines did not support growth as the sole nitrogen source, they did stimulate growth with aspartate as the nitrogen source. Cells produced 14CO2 from minimal medium containing [14C]adenine, which implies allantoin production. However, neither ammonia nor carbamoyl phosphate was produced, which implies that purine catabolism is incomplete and does not provide nitrogen during nitrogen-limited growth. We constructed strains with deletions of two genes whose products might catalyze the first reaction of purine catabolism. Deletion of one eliminated 14CO2 production from [14C]adenine, which implies that its product is necessary for xanthine dehydrogenase activity. We changed the name of this gene to xdhA. The xdhA mutant grew faster with aspartate as a nitrogen source. The mutant also exhibited sensitivity to adenine, which guanosine partially reversed. Adenine sensitivity has been previously associated with defective purine salvage resulting from impaired synthesis of guanine nucleotides from adenine. We propose that xanthine dehydrogenase contributes to this purine interconversion.
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Sun, Runbin, Jingqiu Huang, Na Yang, Jun He, Xiaoyi Yu, Siqi Feng, Yuan Xie, Guangji Wang, Hui Ye, and Jiye Aa. "Purine Catabolism Shows a Dampened Circadian Rhythmicity in a High-fat Diet-Induced Mouse Model of Obesity." Molecules 24, no. 24 (December 10, 2019): 4524. http://dx.doi.org/10.3390/molecules24244524.

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High-calorie diet, circadian rhythms and metabolic features are intimately linked. However, the mediator(s) between nutritional status, circadian rhythms and metabolism remain largely unknown. This article aims to clarify the key metabolic pathways bridging nutritional status and circadian rhythms based on a combination of metabolomics and molecular biological techniques. A mouse model of high-fat diet-induced obesity was established and serum samples were collected in obese and normal mice at different zeitgeber times. Gas chromatography/mass spectrometry, multivariate/univariate data analyses and metabolic pathway analysis were used to reveal changes in metabolism. Metabolites involved in the metabolism of purines, carbohydrates, fatty acids and amino acids were markedly perturbed in accordance with circadian related variations, among which purine catabolism showed a typical oscillation. What’s more, the rhythmicity of purine catabolism dampened in the high-fat diet group. The expressions of clock genes and metabolic enzymes in the liver were measured. The mRNA expression of Xanthine oxidase (Xor) was highly correlated with the rhythmicity of Clock, Rev-erbα and Bmal1, as well as the metabolites involved in purine catabolism. These data showed that a high-fat diet altered the circadian rhythm of metabolic pathways, especially purine catabolism. It had an obvious circadian oscillation and a high-fat diet dampened its circadian rhythmicity. It was suggested that circadian rhythmicity of purine catabolism is related to circadian oscillations of expression of Xor, Uox and corresponding clock genes.
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Yin, Yuling, Riko Katahira, and Hiroshi Ashihara. "Metabolism of Purine Alkaloids and Xanthine in Leaves of Maté (Ilex paraguariensis)." Natural Product Communications 10, no. 5 (May 2015): 1934578X1501000. http://dx.doi.org/10.1177/1934578x1501000503.

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Accumulation and metabolism of purine alkaloids in leaves of maté ( Ilex paraguariensis) were investigated. In winter, leaves accumulated caffeine but not theobromine, indicating that caffeine is the end product of purine alkaloid synthesis in maté. To elucidate the purine alkaloid metabolism in maté leaves, the metabolic fate of [8-14C]theobromine, [8-14C]theophylline, [8-14C]caffeine and [8-14C] xanthine was investigated in the leaf disks of young and mature leaves. In young maté leaves, significant amounts of theobromine and theophylline were utilized for caffeine biosynthesis, but the conversion was not observed in mature leaves. A small amount of theophylline was converted to theobromine. Practically no caffeine catabolism was detected in maté leaves during a 24 h-incubation. Catabolism of theobromine and theophylline via 3-methylxanthine was observed mainly in mature leaves. Xanthine was catabolised extensively via ureides in both young and mature leaves, but limited amounts are also utilized for the synthesis of theobromine, theophylline and caffeine. Possible pathways for the metabolism of purine alkaloids in maté leaves are discussed.
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Muzychka, Oksana, Olexandr Kobzar, Oleg Shablykin, Volodymyr Brovarets, and Andriy Vovk. "5-Substituted N-(9H-purin-6-yl)-1,2-oxazole-3-carboxamides as xanthine oxidase inhibitors." Ukr. Bioorg. Acta 2020, Vol. 15, N1 15, no. 1 (June 30, 2020): 20–25. http://dx.doi.org/10.15407/bioorganica2020.01.020.

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Synthetic 6-substituted purine derivatives are known to exhibit diverse bioactivity. In this paper, a series of N-(9H-purin-6-yl)-1,2-oxazole-3-carboxamide derivatives were synthesized and evaluated in vitro against xanthine oxidase, an enzyme of purine catabolism. The introduction of aryl substituent at position 5 of the oxazole ring was found to increase the inhibition efficiency. Some of the inhibitors containing 5-substituted isoxazole and purine moieties were characterized by IC50 values in the nanomolar range. According to the kinetic data, the most active N-(9H-purin-6-yl)-5-(5,6,7,8-tetrahydronaphthalen-2-yl)-1,2-oxazole-3-carboxamide demonstrated a competitive type of inhibition with respect to the enzyme-substrate. Molecular docking was carried out to elucidate the mechanism of enzyme-inhibitor complex formation. The data obtained indicate that xanthine oxidase may be one of the possible targets for the bioactive purine carboxamides.
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Itakura, M., N. Maeda, and K. Yamashita. "Increased rate of purine biosynthesis in rat liver after bilateral adrenalectomy." American Journal of Physiology-Endocrinology and Metabolism 251, no. 4 (October 1, 1986): E373—E378. http://dx.doi.org/10.1152/ajpendo.1986.251.4.e373.

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In bilaterally adrenalectomized rat liver the increased rate of de novo purine synthesis was shown by the increased [14C]glycine incorporation into hepatic acid-soluble purines with unchanged rapidly miscible glycine pool size and its turnover rate and by the increased rate of chasing of radiolabeled purines. At 24 h after adrenalectomy, the rate of de novo purine synthesis increased by 70%, 5-phosphoribosyl-1-pyrophosphate (PRPP) content increased by 200%, the specific activity of amidophosphoribosyltransferase (EC 2.4.2. 14; ATase) did not change, ATP and GTP showed a 33 and 24% decrease, and AMP and ADP showed a 245 and 38% increase. Combined, the metabolic pool size data reflected an unchanged total inhibitory potential on ATase. Replacement with corticosterone acetate for 24 h partially restored some of these abnormalities. These results suggest that the increase in the rate of de novo purine synthesis in adrenalectomized rat liver is secondary to increased catabolism of purine ribonucleotides and mediated by increased PRPP concentrations.
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Pizzichin, M., M. L. Pandolfi, L. Terzuoli, L. Arezzini, and R. Pagani. "Purine nucleotide catabolism in rat liver." Biochemical Society Transactions 21, no. 2 (May 1, 1993): 189S. http://dx.doi.org/10.1042/bst021189s.

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HADANO, SHINJI, SATOSHI SAKAI, MASASHI OGASAWARA, and AKIRA ITO. "EFFECTS OF EXERCISE INTENSITY ON PURINE CATABOLISM." Japanese Journal of Physical Fitness and Sports Medicine 37, no. 3 (1988): 225–33. http://dx.doi.org/10.7600/jspfsm1949.37.225.

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Felici, C., I. Ciari, L. Terzuoli, B. Porcelli, C. Setacci, M. Giubbolini, and E. Marinello. "Purine Catabolism in Advanced Carotid Artery Plaque." Nucleosides, Nucleotides and Nucleic Acids 25, no. 9-11 (June 2006): 1291–94. http://dx.doi.org/10.1080/15257770600890772.

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Voloshchuk, Oksana, Halyna Kopylchuk, and Andriana Plytus. "Activity of purine nucleotide catabolic enzymes in the liver of rats under conditions of nutritional imbalance." Biolohichni systemy 12, no. 2 (December 23, 2020): 119–24. http://dx.doi.org/10.31861/biosystems2020.02.119.

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The aim of the study was to investigate the activity of purine nucleotide catabolism enzymes, in particular, AMP-deaminase, 5'-nucleotidase, guanosine deaminase, and guanosine phosphorylase and xanthine oxidase in the cytosolic fraction of the liver of rats under conditions of different dietary supply of sucrose and dietary proteins. Enzyme activity was determined by photo colorimetric method: AMP-deaminase activity by the amount of ammonia formed by deamination of AMP, which has a maximum absorption at λ-540 nm and 5'-nucleotidase activity by the amount of Pn formed by hydrolysis of AMP at λ-8. The activity of guanosine phosphorylase, guanosine deaminase and xanthine oxidase was determined by spectrophotometric method. The results of studies have shown that due to consuming a high-sucrose diet in on the background of protein deficiency, the activation of purine nucleotide catabolism is observed and it can lead to disruption of the regulation of energy-dependent processes in liver cells. A critical factor influencing on the state of the purine nucleotide system and the activity of enzymes of their catabolism is alimentary protein deficiency.
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Dissertations / Theses on the topic "Purine catabolism"

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Le, Tissier Paul Roussel. "The biochemical genetics of purine catabolism in mice." Thesis, University of Reading, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236393.

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Kavianipour, Mohammad. "Myocardial energy metabolism in ischemic preconditioning, role of adenosine catabolism." Doctoral thesis, Umeå University, Public Health and Clinical Medicine, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-14.

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Brief episodes of ischemia and reperfusion render the myocardium more resistant to necrosis from a subsequent, otherwise lethal ischemic insult. This phenomenon is called ischemic preconditioning(IP). Today, much is known about the signalling pathways involved in IP; however, the details of the final steps leading to cardioprotection, remain elusive. Adenosine (a catabolite of ATP) plays a major role in the signalling pathways of IP. Following IP there is an unexplained discrepancy between an increased adenosine production (evidenced by increased 5’-nucleotidase activity) and the successively lower adenosine levels observed in the interstitial space. We propose that this discrepancy in adenosine production vs. availability may be due to an increased metabolic utilisation of adenosine by the IP myocardium. According to our hypothesis, IP induces/activates a metabolic pathway involving deamination of adenosine to inosine. Inosine is further catalysed (in presence of Pi) to hypoxanthine and ribose-1-phosphate. Ribose-1-phosphate can be converted to ribose-5-phosphate in a phosphoribomutase reaction. Ribose-5-phosphate is an intermediate of the hexose monophosphate pathway also operative under anaerobic conditions. Hence the ribose moiety of adenosine can be utilised to generate pyruvate and ultimately ATP (via lactate formation) n.b. without any initial ATP investment. Such cost-effective adenosine utilisation may at least partly explain the cardioprotective effect of IP. Objectives & Methods: In the current studies we investigated the role of adenosine metabolism according to the suggested metabolic pathway by addition of adenosine and inhibition of its metabolism during IP as well as by comparing tissue and interstitial levels of key energy-metabolites following different protocols of IP. Furthermore, we studied the importance of the IP protocol with regard to the number of ischemia and reperfusion cycles for the cardioprotective effect of IP. In addition, the validity of the microdialysis technique for experimental in vivo studies of myocardial energy metabolism was evaluated. For these purposes the microdialysis technique, tissue biopsies, and planimetric infarct size estimation in an open chest porcine heart-model was used. Results: Addition of adenosine via microdialysis probes enhanced the interstitial release of inosine, hypoxanthine and lactate in the myocardium of IP-subjects during prolonged ischemia. This finding did not occur in non-preconditioned subjects. Similar addition of deoxyadenosine a non-metabolizable adenosine receptor-agonist, did not evoke the same metabolic response. Purine nucleoside phosphorylase (PNP) is responsible for the conversion of inosine to hypoxanthine being a key enzyme in the above mentioned metabolic pathway. Inclusion of 8' aminoguanosine (a competitive inhibitor of PNP) decreased interstitial hypoxanthine release (as a token of PNP inhibition) and increased the release of taurine (marker of cellular injury) in the ischemic IP myocardium. Addition of inosine (a natural substrate of PNP) reverted these changes. Four IP cycles protected the heart more than one IP cycle as evidenced by morphometric and energy-metabolic data.Proportionally more hypoxanthine was found in the myocardium of IP subjects during prolonged ischemia. The ratio of tissue levels of inosine/hypoxanthine (used as an indicator of PNP activity) was significantly smaller in the IP groups. In addition, myocardial interstitial levels of energy-related metabolites (lactate, adenosine, inosine, and hypoxanthine) obtained by the microdialysis technique correlated with tissue biopsy levels of corresponding metabolites. Conclusions: IP activated a metabolic pathway favouring metabolism of exogenous adenosine to inosine, hypoxanthine and eventually lactate. Inhibition of adenosine metabolism following IP (via inhibition of PNP-activity resulted in enhanced cellular injury.

PNP-activity is proportionally higher in IP-myocardium. Metabolic utilisation of adenosine in IP-myocardium (as outlined above) may represent a costeffective way to produce ATP and at least partly explain the cardioprotective effect of IP. IP protects the myocardium in a graded fashion. Furthermore, we confirmed the validity of the microdialysis technique (in the current setting) for studying dynamic changes of myocardial energy metabolism.

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Baccolini, Chiara [Verfasser]. "Analysis of in vivo purine nucleotide catabolism in Arabidopsis thaliana with focus on nucleoside hydrolase 2 / Chiara Baccolini." Hannover : Gottfried Wilhelm Leibniz Universität Hannover, 2019. http://d-nb.info/1193177146/34.

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Huynh, Hanh Kim. "Physiological, ultrastructural and cytochemical studies on the utilization of various intermediates of the purine catabolism pathway as sole sources of nitrogen by marine phytoplankters." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/27491.

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Eleven species of marine microalgae belonging to six different taxonomic divisions were tested for their ability to grow on allantoin, allantoic acid, hypoxanthine and urea as sole sources of nitrogen. All species were able to utilize the nitrogen atoms of urea but only six of these were able to grow on allantoic acid, while five showed moderate to good growth in hypoxanthine. None was able to utilize allantoin. The study of nickel requirements for the growth of these microalgae on the different sources of nitrogen, together with the results of inhibitor tests suggest that those species capable of utilizing both hypoxanthine and allantoic acid catabolize purines through the standard pathway of purine oxidation described in other microorganisms and higher plants. This pathway leads to the production of urea and its subsequent conversion to utilizable ammonium. In the case of one species, Pavlova lutheri, growth on urea is inhibited by urease inhibitors, while growth in allantoic acid or hypoxanthine occurs in the presence, of urease inhibitors. The results suggest that in this case the catabolic oxidation of purines and their derivatives does not involve urea production and occurs through a pathway different from that observed in the other species. Cells of Amphidinium carterae grown on hypoxanthine undergo major ultrastructural changes. These affect the perichromatinic granules, the dictyosomes and dictyosome-derived vesicles, the distribution of the endoplasmic reticulum, the number of mitochondria and microbodies, and the size and distribution of the vacuolar compartment. Some of these ultrastructural changes, such as increase in endoplasmic reticulum and the number of microbodies, along with the cytochemical demonstration of both uricase and catalase activities within microbodies, support the occurrence in these microalgae of the standard pathway for the catabolic degradation of purines. Cells of both Dunaliella tertiolecta and Pavlova lutheri grown on hypoxanthine also undergo major ultrastructural changes. These affect mainly the endoplasmic reticulum, mitochondria and vacuoles. The effect on mitochondria is particularly interesting since cytochemical tests reveal the presence of both uricase and catalase activities in these organelles. When one takes into consideration that no microbodies are observed in these microalgae and that uricase controls the key step of the formation of allantoin and H₂O₂ through the oxidation of urate, it becomes apparent that in these microalgae mitochondria participate in the oxidative degradation of purines and their derivatives and play a major role in the organic N-budget of these microorganisms.
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Lee, Hakjoo. "Nitrogen regulation of the purine catabolic genes in Neurospora crassa /." The Ohio State University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487681148541111.

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Cecchetto, Gianna. "Catabolisme de purines chez Aspergillus nidulans : caractérisation du transporteur AzgA : analyse de la fixation à l'ADN de l'activateur transcriptionnel UaY." Paris 11, 2003. http://www.theses.fr/2003PA112331.

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Chez Aspergillus nidulans, au moins trois perméases sont impliquées dans le transport des purines. AzgA transporte l’hypoxanthine et l’adénine. UapA transporte l’acide urique et la xanthine. UapC est une perméase mineure qui transporte toutes ces purines. L’expression des gènes uapA et uapC est induite en présence d’acide urique par l’intermédiaire de la protéine UaY et réprimée en présence d’ammonium du fait de l’inactivation de l'activateur transcriptionnel AreA. Ce travail présente la caractérisation du gène azgA et de la protéine qu’il code. AzgA définit un sous-groupe de transporteurs appartenant à la famille Xanthine/uracil permeases, très distante de celui qui comporte UapA et UapC. L’expression d’azgA est induite par d’acide urique et réprimée par l’ammonium. Au cours de la germination des conidiospores, les trois gènes sont induits par d’acide urique, réprimés par l’ammonium bien que nettement moins que dans le mycélium et induits en absence d’acide urique, ce qui pourrait être lié au developpement ou être une réponse spécifique à la carence en source d’azote. La fixation à l’ADN de l’activateur UaY, une protéine à complexe binucléaire à zinc a été analysée. UaY agit sous forme de dimère, le domaine UaY(103-147) étant responsable de cette dimérisation. La Phe112 est importante vis-à-vis de la stabilisation de la structure dimérique, qui est déstabilisée par la mutation F112I. Cette modification diminue l’activation de la transcription d’au moins cinq gènes controlés par UaY ainsi que l’affinité apparente pour l’ADN. Chez les revertants analysés, des mutations intragéniques affectent soit la fixation de UaY sur l’ADN soit sa fonction d’activation
At least three permeases are involved in purine transport in Aspergillus nidulans. The AzgA protein is the main transporter for adenine and hypoxanthine and UapA transport xanthine and uric acid. The UapC protein is a low-capacity transporter for all natural purines. Expression of uapA and uapC genes in mycelium is induced by purines and repressed by ammonium through the action of the pathway-specific UaY regulator and the general GATA factor AreA, respectively. Here we present the characterisation of azgA gene and its protein product. AzgA protein defines an UapA-UapC distant sub-family of Xanthine/uracil permeases family. AzgA expression is induced by uric acid and repressed by ammonium. During the isotropic growth phase of conidial germination, the expression of the three purine transporter genes are induced by uric acid. The ammonium repression is very low. Transcriptional activation occurs in the absence of purine induction and independently of the nitrogen and carbon source present in the medium. This work establishes the presence of a novel system triggering purine transporter transcription during germination. We have studied the UaY-DNA interactions. UaY, a Zn binuclear cluster transcription factor, binds as a dimmer through UaY(103-147) domain. Phe112 is important for the dimmeric structure stabilisation, which is diminished in a F112I mutant. This modification reduces the transcription activation of almost five genes under UaY control as well as its affinity to its targets. Revertants re-establish wild type phenotype by altering the interactions between this activator and its DNA targets or by affecting the activation function
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RIBARD, CARIN. "Etude de la regulation du catabolisme des purines chez aspergillus nidulans : - clonage et caracterisation moleculaire de oxpa. - caracterisation moleculaire de nada." Paris 11, 1999. http://www.theses.fr/1999PA112379.

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Chez aspergillus nidulans, l'expression des genes de structure du catabolisme des purines est induite en presence d'acide urique et reprimee en presence d'ammonium et de glutamine. Deux activateurs controlent l'expression de ces genes de structure : uay, un activateur a complexe binucleaire a zinc, specifique a cette voie, et area, un facteur gata implique dans la repression generale par l'azote. Le gene nada code pour la premiere enzyme du catabolisme des purines, une adenine deaminase. Nada a precedemment ete clone et sequence par n. Oestreicher. Ce travail presente la caracterisation moleculaire de ce gene, ainsi que l'etude de sa regulation. Bien que la proteine nada est homologue aux adenosine deaminases eucaryotes, et non aux adenine deaminases procaryotes, des dosages biochimiques ont demontres que sa fonction biochimique est celle d'une adenine deaminase. Ce resultat revele l'existence d'une nouvelle famille d'adenine deaminases eucaryotes, et remet en question le classement des adenosines deaminases realise par comparaison de sequence. Sa regulation vis a vis de area est tres particuliere, puisque en condition de repression par l'ammonium, son niveau d'expression est plus eleve qu'en condition de non induction. Ceci pourrait etre lie a une competition entre uay et area pour la fixation a leurs cibles. Parallelement, l'etude du mutant oxpa5, deregule pour la regulation du catabolisme des purines, a ete menee. Le gene oxpa a ete clone par marche chromosomique, et sa sequence revele qu'il code une adenylosuccinate synthetase (ass). Il a ete demontre que oxpa correspond au locus adb, caracterise comme etant celui de l'ass d'a. Nidulans, auparavant mal cartographie. La mutation oxpa5 correspond a un changement d'acide amine dans un domaine tres conserve parmi les ass. Le phenotype pleitropique de ce mutant est compatible avec l'hypothese que cette mutation entraine une diminution des parametres cinetiques de l'enzyme.
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OESTREICHER, NATHALIE. "Etude moleculaire de la regulation du catabolisme des purines chez aspergillus nidulans : caracterisation du gmene de l'urate oxydase. analyse fonctionnelle du regulateur positif." Paris 11, 1991. http://www.theses.fr/1991PA112276.

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L'urate oxydase d'aspergillus nidulans, codee par le gene uaz, est une proteine de 319 acides amines. Elle presente une homologie de 36% avec l'urate oxydase de rat. La comparaison avec sept autres urates oxydases a mis en evidence la conservation du site potentiel de fixation du cuivre et du signal putatif d'entree dans les peroxysomes. Une analyse par northern de l'expression du gene uaz a confirme que ce gene est inductible par l'acide 2-thiourique (analogue de l'inducteur naturel: l'acide urique) et repressible par l'ammonium. L'induction et une partie du niveau de base du gene uaz ont besoin des produits fonctionnels des genes de regulation uay et area (charge de la repression generalisee par l'azote). Le produit du gene uay est necessaire pour l'expression de huit genes codant pour des enzymes et permeases du catabolisme des purines. L'etude fonctionnelle de ce regulateur positif a ete realisee en analysant 15 revertants d'un mutant de perte de fonction uay205 (deletion de 16 pb a la fin du gene) et de six mutants de gain de fonction. L'analyse des 15 revertants montre que les 201 derniers residus de la proteine ne sont pas essentiels pour sa fonction et qu'ils ne contiennent pas le site de fixation du co-inducteur ou d'un eventuel regulateur negatif. Une partie de la region carboxy-terminale de uay pourrait etre en contact avec d'autres proteines ou servir au maintien de la structure tertiaire. Parmi les six mutants de gain de fonction, cinq sont dus a une erreur de recombinaison, qui est situee en dehors de l'intervalle de crossig-over
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Casartelli, Alberto. "Purine Catabolism in Wheat: Source of Nutrients and Protective Metabolites." Thesis, 2018. http://hdl.handle.net/2440/123271.

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Purine catabolism is known to have a dual function in recycling nitrogen (N) and carbon (C) atoms present in the heterocyclic purine ring and participating in stress signalling through the stimulation of ABA metabolism by allantoin, an intermediate in the pathway. However, little information was available of the functions in cereals and, in particular, bread wheat. The aims of this PhD thesis was to investigate the role of purine catabolism and allantoin in Australian bread wheat (Triticum aestivum) genotypes (RAC875 and Mace) grown under N deficiency and water deficit. Firstly, the purine catabolic genes, coding for seven enzymes in total, were identified and annotated in the hexaploid bread wheat genome of cv. Chinese Spring. The analysis revealed 24 loci associated with the enzyme genes. Interestingly, there was a duplication of the xanthine dehydrogenase gene, namely TaXDH1 and TaXDH2. Sequence analysis of the TaXDH2 homeologs located on chromosome group 6 appeared to be either non-functional (TaXDH2-6AS/6BS) or with an inactive xanthine substrate binding site (TaXDH2-6DS). Protein structure modelling and a unique expression pattern under stress indicated that, TaXDH2-6DS may have a novel function in wheat. Characterisation of allantoin and transcription of purine catabolic genes under N and water restrictions, revealed that allantoin levels were reduced (22-fold) when N was limiting, whilst it tended to accumulate in large amounts under drought (up to 30-fold compared to well-watered plants). The latter may suggest allantoin is used as a temporary N sink as the N assimilatory pathway (GS/GOGAT cycle) is likely to have a reduced capacity in plants growing in water deficit conditions. This would prevent the accumulation of ammonium that is toxic at high concentrations and reduce ammonia emissions from plants leaves. The reduction or accumulation of allantoin under drought and N stress appeared transcriptionally regulated by purine catabolic genes. In particular, transcription of TaALN, coding for the allantoin-degrading enzyme allantoinase, oppositely reflected the levels of allantoin in the tissue. Further growth studies showed that wheat seedlings, when re-supplied with xanthine or allantoin as their sole N source after short-term N starvation, had growth rates which were equivalent to plants grown with inorganic nitrogen. This suggests that the N recycled through the purine catabolic pathway can support the growth of wheat. The data also provided evidence that allantoin takes part in N remobilisation during natural senescence. Sequence analysis of TaALN homeologs in a large number of bread wheat accessions highlighted substantial genetic variability when compared to the reference genome of Chinese Spring. Candidate accessions with nucleotide polymorphisms in regulatory elements or in the coding sequence were identified and represent valuable material for future studies. The outcomes of this PhD project provide the ground work for future fundamental research in wheat focussing on the dual role of purine catabolism in N recycling and abiotic stress. In addition, the candidate accessions identified, besides representing useful experimental material, could ultimately be used for breeding purposes. Additional strategies will include genetic engineering of target genes in the pathway that may lead to improved wheat growth and yields in unfavourable environments.
Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food & Wine, 2018
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Book chapters on the topic "Purine catabolism"

1

Cohen, Amos, and Jerzy Barankiewicz. "Purine Ribonucleotide and Deoxyribonucleotide Catabolism in Lymphocytes." In Purine and Pyrimidine Metabolism in Man V, 561–65. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4684-5104-7_94.

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2

Terzuoli, Lucia, Maria Pizzichini, Anna Di Stefano, Brunetta Porcelli, Antonella Tabucchi, and Roberto Pagani. "Purine Nucleotide Catabolism in Rat Liver After Castration." In Advances in Experimental Medicine and Biology, 297–300. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4899-2638-8_67.

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3

Bontemps, F., G. Van den Berghe, and H. G. Hers. "Pathways of Adenine Nucleotide Catabolism in Human Erythrocytes." In Purine and Pyrimidine Metabolism in Man V, 329–36. New York, NY: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4684-1248-2_53.

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4

Schopf, Gerhard, Michael Havel, Roland Fasol, and Mathias M. Müller. "Enzyme Activities of Purine Catabolism and Salvage in Human Muscle Tissue." In Purine and Pyrimidine Metabolism in Man V, 507–9. New York, NY: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4684-1248-2_78.

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5

Barankiewicz, Jerzy, and Amos Cohen. "Ethanol Induced Nucleotide Catabolism in Mouse T Lymphoblastoid Cells in Vitro." In Purine and Pyrimidine Metabolism in Man V, 227–30. New York, NY: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4684-1248-2_34.

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6

Helland, S., and P. M. Ueland. "Determination of S-Adenosylhomocysteine in Tissues Following Pharmacological Inhibition of S-Adenosylhomocysteine Catabolism." In Purine and Pyrimidine Metabolism in Man V, 663–66. New York, NY: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4684-1248-2_103.

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7

van Waeg, Geert, Frank Niklasson, and Carl-Henric de Verdier. "Deamination of Guanine to Xanthine: A Metabolic Pathway of Underestimated Importance in Human Purine Catabolism?" In Purine and Pyrimidine Metabolism in Man V, 425–30. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4684-5104-7_70.

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8

Kather, H. "Beta Adrenergic Receptor Mediated Stimulation of Adenine Nucleotide Catabolism and Purine Release in Human Adipocytes." In Purines in Cellular Signaling, 120–25. New York, NY: Springer New York, 1990. http://dx.doi.org/10.1007/978-1-4612-3400-5_20.

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9

Wortmann, Robert L., Judith A. Veum, and John W. Rachow. "Purine Catabolic Enzymes in Human Synovial Fluids." In Advances in Experimental Medicine and Biology, 393–98. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4684-5673-8_64.

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Gojkovic, Zoran, Silvia Paracchini, and Jure Piskur. "A New Model Organism for Studying the Catabolism of Pyrimidines and Purines." In Advances in Experimental Medicine and Biology, 475–79. Boston, MA: Springer US, 1998. http://dx.doi.org/10.1007/978-1-4615-5381-6_94.

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