Metabolism of Uracil by Germinating Jack Pine Seedlings

Durzan, D. J.; Pitel, J. A.; Mia, A. J.; Ramaiah, P. K.

doi:10.1139/x73-029

Cited by 13 publications

(9 citation statements)

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“…These two metabolites of uracil catabolism, also found during somatic embryo maturation (Ashihara et al, in press), are indicative of an active reductive pathway of uracil catabolism. A similar degradation pathway was also reported in other plant species (Durzan et al, 1973;Ashihara, 1977;Kanamori-Fukuda et al, 1981).…”

Section: Discussionsupporting

confidence: 83%

Changs in pyrimidine nucleotide biosynthesis during germination of white spruce (picea glauca) somatic embryos

Stasolla

Loukanina

Ashihara

et al. 2001

In Vitro Cell.Dev.Biol.-Plant

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Changes in pyrimidine metabolism were investigated in germinating white spruce somatic embryos by following the metabolic fate of [2-14 C]uracil and [2-14 C]uridine, intermediate metabolites of the salvage pathway and [6-14 C]orotic acid, a central metabolite of the de novo nucleotide biosynthesis. An active uridine salvage was found to be responsible for the enlargement of the nucleotide pool at the inception of germination. Uridine kinase, which catalyzes the conversion of uridine to uridine monophosphate (UMP), was found to be very active in partially dried embryos and during the early phases of imbibition. The contribution of uracil to the nucleotide pool was negligible since a large amount of radioactivity from [2-14 C]uracil was recovered in degradation products. As germination progressed, the decline of the uridine salvage pathway was concomitant with an increase of the de novo biosynthetic pathway. The central enzyme of the de novo pathway, orotate phosphoribosyltransferase, showed increased activity and contributed to the larger amount of orotate being anabolized. These results suggest that although both the salvage and de novo pathways operate in germinating white spruce somatic embryos, their contribution to the enlargement of the nucleotide pool appears tightly regulated as germination progresses.

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Section: Discussionsupporting

confidence: 83%

Changs in pyrimidine nucleotide biosynthesis during germination of white spruce (picea glauca) somatic embryos

Stasolla

Loukanina

Ashihara

et al. 2001

In Vitro Cell.Dev.Biol.-Plant

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“…1b), as also reported in other systems (Durzan et al 1973;Ashihara et al 2000;Ashihara 2002, 2006a;Sato and Ashihara 2009). Degradation of uracil was extensive (more than 80% of total incorporation) conWrming previous reports (Ashihara et al 2000).…”

Section: Degradation Of Purine and Pyrimidine Nucleotidessupporting

confidence: 85%

Brassinolide-improved development of Brassica napus microspore-derived embryos is associated with increased activities of purine and pyrimidine salvage pathways

Belmonte

Elhiti

Ashihara

et al. 2010

Planta

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Cellular brassinolide (BL) levels regulate the development of Brassica napus microspore-derived embryos (MDEs). Synthesis and degradation of nucleotides were measured on developing MDEs treated with BL or brassinazole (BrZ), a biosynthetic inhibitor of BL. Purine metabolism was investigated by following the metabolic fate of (14)C-labelled adenine and adenosine, substrates of the salvage pathway, and inosine, an intermediate of both salvage and degradation pathways. For pyrimidine, orotic acid, uridine and uracil were employed as markers for the de novo (orotic acid), salvage (uridine and uracil), and degradation (uracil) pathways. Our results indicate that utilization of adenine, adenosine, and uridine for nucleotides and nucleic acids increased significantly in BL-treated embryos at day 15 and remained high throughout the culture period. These metabolic changes were ascribed to the activities of the respective salvage enzymes: adenine phosphoribosyltransferase (EC 2.4.2.7), adenosine kinase (EC 2.7.1.20), and uridine kinase (EC 2.7.1.48), which were induced by BL applications. The BL promotion of salvage synthesis was accompanied by a reduction in the activities of the degradation pathways, suggesting the presence of competitive anabolic and catabolic mechanisms utilizing the labelled precursors. In BrZ-treated embryos, with depleted BL levels, the salvage activity of both purine and pyrimidine nucleotides was reduced and this was associated to structural abnormalities and poor embryonic performance. In these embryos, the activities of major salvage enzymes were consistently lower to those measured in their control (untreated) counterparts.

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“…Compared to other plants, a very active adenine salvage pathway for nucleotide biosynthesis was noted. For pyrimidines, Durzan and his co-workers (Durzan et al 1973, Pitel andDurzan 1975) examined the metabolism of exogenously supplied radioactive uracil, thymine, thymidine, and orotate in Pinus banksiana seeds and seedlings. Biosynthesis of nucleic acids via the de novo and salvage pathways of pyrimidine nucleotides and degradation of pyrimidine bases were demonstrated by their tracer experiments.…”

Section: Introductionmentioning

confidence: 99%

Purine and pyrimidine metabolism in cultured white spruce (Picea glauca) cells: Metabolic fate of 14 C-labeled precursors and activity of key enzymes

Ashihara¹,

Stasolla²,

Loukanina³

et al. 2000

Physiol Plant

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In order to examine the biosynthesis, interconversion, and acid, and CO 2 . Among these 3 precursors, the radioactivity degradation of purine and pyrimidine nucleotides in white from [8-14 C]inosine was predominantly incorporated into CO 2 . These results suggest the operation of a conventional degrada-spruce cells, radiolabeled adenine, adenosine, inosine, uracil, tion pathway. Both [2-14 C]uracil and [2-14 C]uridine were con-uridine, and orotic acid were supplied exogenously to the cells and the overall metabolism of these compounds was monitored. verted to uridine nucleotides and incorporated into uracil and [8-14 C]adenine and [8-14 C]adenosine were metabolized to cytosine bases of nucleic acids. The salvage enzymes, uridine kinase and uracil phosphoribosyltransferase, were detected in adenylates and part of the adenylates were converted to guanylates and incorporated into both adenine and guanine white spruce extracts. [6-14 C]orotic acid, an intermediate of the de novo pyrimidine biosynthesis, was efficiently converted into bases of nucleic acids. A small amount of [8-14 C]inosine was uridine nucleotides and also incorporated into uracil and converted into nucleotides and incorporated into both adenine cytosine bases of nucleic acids. High activity of orotate and guanine bases of nucleic acids. High adenosine kinase and phosphoribosyltransferase was observed in the extracts. A large adenine phosphoribosyltransferase activities in the extract suggested that adenosine and adenine were converted to AMP by proportion of radioactivity from [2-14 C]uracil was recovered as CO 2 and -ureidopropionate. Thus, a reductive pathway of these enzymes. No adenosine nucleosidase activity was deuracil degradation is functional in these cells. Therefore, white tected. Inosine was apparently converted to AMP by inosine spruce cells in culture demonstrate both the de novo and salvage kinase and/or a non-specific nucleoside phosphotransferase. pathways of purine and pyrimidine metabolism, as well as some The radioactivity of [8-14 C]adenosine, [8-14 C]adenine, and [8-14 C]inosine was also detected in ureide, especially allantoic degradation of the substrates into CO 2

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Metabolism of Uracil by Germinating Jack Pine Seedlings

Cited by 13 publications

References 0 publications

Changs in pyrimidine nucleotide biosynthesis during germination of white spruce (picea glauca) somatic embryos

Changs in pyrimidine nucleotide biosynthesis during germination of white spruce (picea glauca) somatic embryos

Brassinolide-improved development of Brassica napus microspore-derived embryos is associated with increased activities of purine and pyrimidine salvage pathways

Purine and pyrimidine metabolism in cultured white spruce (Picea glauca) cells: Metabolic fate of 14 C-labeled precursors and activity of key enzymes

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