Pyrimidine metabolism in seeds and seedlings of jack pine (<i>Pinus banksiana</i>)

Pitel, J. A.; Durzan, D. J.

doi:10.1139/b75-083

Cited by 12 publications

(9 citation statements)

References 30 publications

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“…6) indicates that the ability to synthesize pyrimidine nucleotides de novo was low in dry embryos and gradually increased as germination progressed. Similarly to our observation, an extensive amount of the radioactivity from labeled orotate was recovered into nucleic acids of jack pine seedlings (Pitel and Durzan, 1975). The relatively poor utilization of orotate at the end of the desiccation period (10 d PDT) may be ascribed to the low specific activity of orotate phosphoribosyl transferase (OPRT) ( Table 1) which, in concert with orotidine monophosphate decarboxylase (Ashihara, 1978;Santoso and Thornburg, 1998) catalyzes the conversion of orotate to UMP (steps 2 and 9, Fig.…”

Section: Discussionsupporting

confidence: 81%

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: 81%

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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“…Although the exact degradation pathway of orotate could not be estimated from the data obtained here, orotate may be converted to uridine nucleotides and then catabolized via uracil by the reductive pathway. This speculation does not contradict the report of Pitel and Durzan (1975), who demonstrated that a small amount of radioactivity from [4-14 C]orotic acid was incorporated into i-alanine in jack pine seedlings. Further degradation of i-alanine may be rapid in white spruce cells, because radioactivity from [6-14 C]orotic acid was recovered as 14 CO 2 .…”

Section: Discussionsupporting

confidence: 69%

“…Compared with uridine and uracil, orotic acid was a good precursor for the pyrimidine nucleotides, especially for nucleic acids in white spruce. Pitel and Durzan (1975) also reported that most of the radioactivity from [4-14 C]orotate was incorporated into nucleic acids in jack pine seedlings. These results obtained from conifers are different from the data obtained from suspension-cultured C. roseus cells (Kanamori-Fukuda et al 1981) and carrot cells , where uridine is the most efficient precursor for the nucleotides and nucleic acid synthesis.…”

Section: Discussionmentioning

confidence: 94%

“…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%

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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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“…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 and Durzan 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 ¹⁴C‐labeled precursors and activity of key enzymes

Ashihara

Stasolla

Loukanina

et al. 2000

Physiologia Plantarum

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In order to examine the biosynthesis, interconversion, and degradation of purine and pyrimidine nucleotides in white spruce cells, radiolabeled adenine, adenosine, inosine, uracil, uridine, and orotic acid were supplied exogenously to the cells and the overall metabolism of these compounds was monitored. [8‐14C]adenine and [8‐14C]adenosine were metabolized to adenylates and part of the adenylates were converted to guanylates and incorporated into both adenine and guanine bases of nucleic acids. A small amount of [8‐14C]inosine was converted into nucleotides and incorporated into both adenine and guanine bases of nucleic acids. High adenosine kinase and adenine phosphoribosyltransferase activities in the extract suggested that adenosine and adenine were converted to AMP by these enzymes. No adenosine nucleosidase activity was detected. Inosine was apparently converted to AMP by inosine kinase and/or a non‐specific nucleoside phosphotransferase. The radioactivity of [8‐14C]adenosine, [8‐14C]adenine, and [8‐14C]inosine was also detected in ureide, especially allantoic acid, and CO2. Among these 3 precursors, the radioactivity from [8‐14C]inosine was predominantly incorporated into CO2. These results suggest the operation of a conventional degradation pathway. Both [2‐14C]uracil and [2‐14C]uridine were converted to uridine nucleotides and incorporated into uracil and cytosine bases of nucleic acids. The salvage enzymes, uridine kinase and uracil phosphoribosyltransferase, were detected in white spruce extracts. [6‐14C]orotic acid, an intermediate of the de novo pyrimidine biosynthesis, was efficiently converted into uridine nucleotides and also incorporated into uracil and cytosine bases of nucleic acids. High activity of orotate phosphoribosyltransferase was observed in the extracts. A large proportion of radioactivity from [2‐14C]uracil was recovered as CO2 and β‐ureidopropionate. Thus, a reductive pathway of uracil degradation is functional in these cells. Therefore, white spruce cells in culture demonstrate both the de novo and salvage pathways of purine and pyrimidine metabolism, as well as some degradation of the substrates into CO2.

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Pyrimidine metabolism in seeds and seedlings of jack pine (Pinus banksiana)

Cited by 12 publications

References 30 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

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

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

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Pyrimidine metabolism in seeds and seedlings of jack pine (Pinus banksiana)

Cited by 12 publications

References 30 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

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

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

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