The effect of glutamine concentration on the activity of carbamoyl-phosphate synthase II and on the incorporation of [3H]thymidine into DNA in rat mesenteric lymphocytes stimulated by phytohaemagglutinin

Z. Szondy, E. A. Newsholme

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Abstract

The maximum catalytic activities of carbamoyl-phosphate synthase II, a limiting enzyme for pyrimidine nucleotide synthesis, are very much less than those of glutaminase, a limiting enzyme for glutamine utilization, in lymphocytes and macrophages; and the flux through the pathway for pyrimidine formation de novo is only about 0.4% of the rate of glutamine utilization by lymphocytes. The K(m) of synthase II for glutamine is about 16 μM and the concentration of glutamine necessary to stimulate lymphocyte proliferation half-maximally is about 21 μM. This agreement suggests that the importance of glutamine for these cells is provision of nitrogen for biosynthesis of pyrimidine nucleotides (and probably purine nucleotides). However, the glutamine concentration necessary for half-maximal stimulation of glutamine utilization (glutaminolysis) by the lymphocytes is 2.5 mM. The fact that the rate of glutamine utilization by lymphocytes is markedly in excess of the rate of the pathway for pyrimidine nucleotide synthesis de novo and that the K(m) and 'half-maximal concentration' values are so different, suggests that the glutaminolytic pathway is independent of the use of glutamine nitrogen for pyrimidine synthesis.

Original languageEnglish
Pages (from-to)979-983
Number of pages5
JournalBiochemical Journal
Volume261
Issue number3
Publication statusPublished - 1989

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Carbamyl Phosphate
Lymphocytes
Phytohemagglutinins
Glutamine
Thymidine
Rats
DNA
Pyrimidine Nucleotides
Nitrogen
Glutaminase
Purine Nucleotides
Macrophages
Biosynthesis
Enzymes
Catalyst activity
Fluxes

ASJC Scopus subject areas

  • Biochemistry

Cite this

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abstract = "The maximum catalytic activities of carbamoyl-phosphate synthase II, a limiting enzyme for pyrimidine nucleotide synthesis, are very much less than those of glutaminase, a limiting enzyme for glutamine utilization, in lymphocytes and macrophages; and the flux through the pathway for pyrimidine formation de novo is only about 0.4{\%} of the rate of glutamine utilization by lymphocytes. The K(m) of synthase II for glutamine is about 16 μM and the concentration of glutamine necessary to stimulate lymphocyte proliferation half-maximally is about 21 μM. This agreement suggests that the importance of glutamine for these cells is provision of nitrogen for biosynthesis of pyrimidine nucleotides (and probably purine nucleotides). However, the glutamine concentration necessary for half-maximal stimulation of glutamine utilization (glutaminolysis) by the lymphocytes is 2.5 mM. The fact that the rate of glutamine utilization by lymphocytes is markedly in excess of the rate of the pathway for pyrimidine nucleotide synthesis de novo and that the K(m) and 'half-maximal concentration' values are so different, suggests that the glutaminolytic pathway is independent of the use of glutamine nitrogen for pyrimidine synthesis.",
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AU - Newsholme, E. A.

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N2 - The maximum catalytic activities of carbamoyl-phosphate synthase II, a limiting enzyme for pyrimidine nucleotide synthesis, are very much less than those of glutaminase, a limiting enzyme for glutamine utilization, in lymphocytes and macrophages; and the flux through the pathway for pyrimidine formation de novo is only about 0.4% of the rate of glutamine utilization by lymphocytes. The K(m) of synthase II for glutamine is about 16 μM and the concentration of glutamine necessary to stimulate lymphocyte proliferation half-maximally is about 21 μM. This agreement suggests that the importance of glutamine for these cells is provision of nitrogen for biosynthesis of pyrimidine nucleotides (and probably purine nucleotides). However, the glutamine concentration necessary for half-maximal stimulation of glutamine utilization (glutaminolysis) by the lymphocytes is 2.5 mM. The fact that the rate of glutamine utilization by lymphocytes is markedly in excess of the rate of the pathway for pyrimidine nucleotide synthesis de novo and that the K(m) and 'half-maximal concentration' values are so different, suggests that the glutaminolytic pathway is independent of the use of glutamine nitrogen for pyrimidine synthesis.

AB - The maximum catalytic activities of carbamoyl-phosphate synthase II, a limiting enzyme for pyrimidine nucleotide synthesis, are very much less than those of glutaminase, a limiting enzyme for glutamine utilization, in lymphocytes and macrophages; and the flux through the pathway for pyrimidine formation de novo is only about 0.4% of the rate of glutamine utilization by lymphocytes. The K(m) of synthase II for glutamine is about 16 μM and the concentration of glutamine necessary to stimulate lymphocyte proliferation half-maximally is about 21 μM. This agreement suggests that the importance of glutamine for these cells is provision of nitrogen for biosynthesis of pyrimidine nucleotides (and probably purine nucleotides). However, the glutamine concentration necessary for half-maximal stimulation of glutamine utilization (glutaminolysis) by the lymphocytes is 2.5 mM. The fact that the rate of glutamine utilization by lymphocytes is markedly in excess of the rate of the pathway for pyrimidine nucleotide synthesis de novo and that the K(m) and 'half-maximal concentration' values are so different, suggests that the glutaminolytic pathway is independent of the use of glutamine nitrogen for pyrimidine synthesis.

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