scholarly journals The influence of ammonia on purine and pyrimidine nucleotide biosynthesis in rat liver and brain in vitro

1978 ◽  
Vol 172 (3) ◽  
pp. 457-464 ◽  
Author(s):  
Stephen D. Skaper ◽  
William E. O'Brien ◽  
Irwin A. Schafer
Keyword(s):  
De Novo ◽  
Liver Homogenate ◽  
Purine Biosynthesis ◽  
Purine Nucleotide ◽  
Carbamoyl Phosphate ◽  
Phosphoribosyl Pyrophosphate ◽  
Nucleotide Synthesis ◽  
Nucleotide Biosynthesis ◽  
Pyrimidine Nucleotide

1. The effect of ammonia on purine and pyrimidine nucleotide biosynthesis was studied in rat liver and brain in vitro. The incorporation of NaH14CO3 into acid-soluble uridine nucleotide (UMP) in liver homogenates and minces was increased 2.5–4-fold on incubation with 10mm-NH4Cl plus N-acetyl-l-glutamate, but not with either compound alone. 2. The incorporation of NaH14CO3 into orotic acid was increased 3–4-fold in liver homogenate with NH4Cl plus acetylglutamate. 3. The 5-phosphoribosyl 1-pyrophosphate content of liver homogenate was decreased by 50% after incubation for 10min with 10mm-NH4Cl plus acetylglutamate. 4. Concomitant with this decrease in free phosphoribosyl pyrophosphate was a 40–50% decrease in the rates of purine nucleotide synthesis, both de novo and from the preformed base. 5. Subcellular fractionation of liver indicated that the effects of NH4Cl plus acetylglutamate on pyrimidine and purine biosynthesis required a mitochondrial fraction. This effect of NH4Cl plus acetylglutamate could be duplicated in a mitochondria-free liver fraction with carbamoyl phosphate. 6. A similar series of experiments carried out with rat brain demonstrated a significant, though considerably smaller, effect on UMP synthesis de novo and purine base reutilization. 7. These data indicate that excessive amounts of ammonia may interfere with purine nucleotide biosynthesis by stimulating production of carbamoyl phosphate through the mitochondrial synthetase, with the excess carbamoyl phosphate in turn increasing pyrimidine nucleotide synthesis de novo and diminishing the phosphoribosyl pyrophosphate available for purine biosynthesis.

scholarly journals A Review of the Potential Utility of Mycophenolate Mofetil as a Cancer Therapeutic

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Nazanin Majd ◽  
Kazutaka Sumita ◽  
Hirofumi Yoshino ◽  
Dillon Chen ◽  
Jumpei Terakawa ◽  
...  
Keyword(s):  
Mycophenolate Mofetil ◽  
Signaling Pathways ◽  
De Novo ◽  
Cancer Therapeutics ◽  
Inosine Monophosphate Dehydrogenase ◽  
Purine Nucleotide ◽  
Antitumor Effects ◽  
Nucleotide Synthesis ◽  
Potential Target

Tumor cells adapt to their high metabolic state by increasing energy production. To this end, current efforts in molecular cancer therapeutics have been focused on signaling pathways that modulate cellular metabolism. However, targeting such signaling pathways is challenging due to heterogeneity of tumors and recurrent oncogenic mutations. A critical need remains to develop antitumor drugs that target tumor specific pathways. Here, we discuss an energy metabolic pathway that is preferentially activated in several cancers as a potential target for molecular cancer therapy. In vitro studies have revealed that many cancer cells synthesize guanosine triphosphate (GTP), via the de novo purine nucleotide synthesis pathway by upregulating the rate limiting enzyme of this pathway, inosine monophosphate dehydrogenase (IMPDH). Non-proliferating cells use an alternative purine nucleotide synthesis pathway, the salvage pathway, to synthesize GTP. These observations pose IMPDH as a potential target to suppress tumor cell growth. The IMPDH inhibitor, mycophenolate mofetil (MMF), is an FDA-approved immunosuppressive drug. Accumulating evidence shows that, in addition to its immunosuppressive effects, MMF also has antitumor effects via IMPDH inhibition in vitro and in vivo. Here, we review the literature on IMPDH as related to tumorigenesis and the use of MMF as a potential antitumor drug.

scholarly journals The Effect of Reticulocytosis in the Rabbit on the Activities of Enzymes in Pyrimidine Biosynthesis

Blood ◽  
1962 ◽  
Vol 19 (5) ◽  
pp. 593-600 ◽  
Author(s):  
MYRON LOTZ ◽  
LLOYD H. SMITH
Keyword(s):  
De Novo ◽  
Pyrimidine Biosynthesis ◽  
Purine Nucleotide ◽  
Nucleotide Biosynthesis ◽  
Mature Erythrocyte ◽  
Pyrimidine Nucleotide

Abstract Five sequential enzymes leading to the formation of uridine-5'-phosphate were studied in acetophenylhydrazine-induced reticulocytes in the rabbit. All of these enzymes—aspartate carbamyltransferase, dihydroorotase, dihydroorotic dehydrogenase, orotidylic pyrophosphorylase, and orotidylic decarboxylase—decreased markedly in activity during in vivo maturation and aging of the reticulocytes. In analogy to previous studies on purine nucleotide biosynthesis, it is concluded that the reticulocyte, but not the mature erythrocyte, is capable of de novo pyrimidine nucleotide biosynthesis.

scholarly journals Down-Regulation of Phosphoribosyl Pyrophosphate Synthetase 1 Inhibits Neuroblastoma Cell Proliferation

Cells ◽  
2019 ◽  
Vol 8 (9) ◽  
pp. 955
Author(s):  
Jifu Li ◽  
Junhong Ye ◽  
Shunqin Zhu ◽  
Hongjuan Cui
Keyword(s):  
Cell Proliferation ◽  
De Novo ◽  
Neuroblastoma Cell ◽  
Neuroblastoma Cells ◽  
Phosphoribosyl Pyrophosphate ◽  
Down Regulation ◽  
Nucleotide Synthesis ◽  
Phosphoribosyl Pyrophosphate Synthetase

Phosphoribosyl pyrophosphate synthetase 1 (PRPS1) is a key enzyme in de novo nucleotide synthesis and nucleotide salvage synthesis pathways that are critical for purine and pyrimidine biosynthesis. Abnormally high expression of PRPS1 can cause many diseases, including hearing loss, hypotonia, and ataxia, in addition to being associated with neuroblastoma. However, the role of PRPS1 in neuroblastoma is still unclear. In this study, we found that PRPS1 was commonly expressed in neuroblastoma cells and was closely related to poor prognosis for cancer. Furthermore, down-regulation of PRPS1 inhibited neuroblastoma cell proliferation and tumor growth in vitro and in vivo via disturbing DNA synthesis. This study provides new insights into the treatment of neuroblastoma patients and new targets for drug development.

scholarly journals 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

1989 ◽  
Vol 261 (3) ◽  
pp. 979-983 ◽  
Author(s):  
Z Szondy ◽  
E A Newsholme
Keyword(s):  
De Novo ◽  
Glutamine Concentration ◽  
Carbamoyl Phosphate ◽  
Purine Nucleotides ◽  
Pyrimidine Nucleotides ◽  
Nucleotide Synthesis ◽  
Pyrimidine Synthesis ◽  
Pyrimidine Nucleotide ◽  
Formation De Novo ◽  
Phosphate Synthase

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 Km of synthase II for glutamine is about 16 microM and the concentration of glutamine necessary to stimulate lymphocyte proliferation half-maximally is about 21 microM. 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 Km and ‘half-maximal concentration’ values are so different, suggests that the glutaminolytic pathway is independent of the use of glutamine nitrogen for pyrimidine synthesis.

scholarly journals Metabolic interaction between amino acid deprivation and cisplatin synergistically reduces phosphoribosyl-pyrophosphate and augments cisplatin cytotoxicity

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Nisreen Wahwah ◽  
Debanjan Dhar ◽  
Hui Chen ◽  
Shunhui Zhuang ◽  
Adriano Chan ◽  
...  
Keyword(s):  
Amino Acid ◽  
Essential Amino Acid ◽  
De Novo ◽  
Synthetase Activity ◽  
Amino Acid Deprivation ◽  
Phosphoribosyl Pyrophosphate ◽  
Nucleotide Synthesis ◽  
Intracellular Phosphate ◽  
Dna Strand

AbstractCisplatin is a mainstay of cancer chemotherapy. It forms DNA adducts, thereby activating poly(ADP-ribose) polymerases (PARPs) to initiate DNA repair. The PARP substrate NAD+ is synthesized from 5-phosphoribose-1-pyrophosphate (PRPP), and we found that treating cells for 6 h with cisplatin reduced intracellular PRPP availability. The decrease in PRPP was likely from (1) increased PRPP consumption, because cisplatin increased protein PARylation and PARP1 shRNA knock-down returned PRPP towards normal, and (2) decreased intracellular phosphate, which down-regulated PRPP synthetase activity. Depriving cells of a single essential amino acid decreased PRPP synthetase activity with a half-life of ~ 8 h, and combining cisplatin and amino acid deprivation synergistically reduced intracellular PRPP. PRPP is a rate-limiting substrate for purine nucleotide synthesis, and cisplatin inhibited de novo purine synthesis and DNA synthesis, with amino acid deprivation augmenting cisplatin’s effects. Amino acid deprivation enhanced cisplatin’s cytotoxicity, increasing cellular apoptosis and DNA strand breaks in vitro, and intermittent deprivation of lysine combined with a sub-therapeutic dose of cisplatin inhibited growth of ectopic hepatomas in mice. Augmentation of cisplatin’s biochemical and cytotoxic effects by amino acid deprivation suggest that intermittent deprivation of an essential amino acid could allow dose reduction of cisplatin; this could reduce the drug’s side effects, and allow its use in cisplatin-resistant tumors.

scholarly journals De novo purine nucleotide biosynthesis mediated by amidophosphoribosyl transferase is required for conidiation and essential for the successful host colonization of Magnaporthe oryzae

2021 ◽  
Author(s):  
Osakina Aron ◽  
Min Wang ◽  
Jiayuan Guo ◽  
Jagero Frankline Otieno ◽  
Qussai Zuriegat ◽  
...  
Keyword(s):  
Fungal Pathogens ◽  
De Novo ◽  
Host Cells ◽  
Purine Biosynthesis ◽  
Pcr Analysis ◽  
Pathogenicity Test ◽  
Purine Nucleotide ◽  
In Planta ◽  
Host Colonization ◽  
Nucleotide Biosynthesis

Amidophosphoribosyl transferase catalyzes the first step of the purine nucleotide biosynthesis by converting 5-phosphoribosyl-1-pyrophosphate into 5-phosphoribosyl-1-amine. In this study, we identified and characterized the functions of MoAde4, an ortholog of yeast Ade4 in the rice blast fungus. MoAde4 is a 537-amino acid protein containing the GATase_6 and pribosyltran domains. Quantitative real-time PCR analysis showed MoADE4 transcripts were highly expressed during conidiation, early-infection, and late-infection stages of the fungus. Disruption of MoADE4 gene resulted in ΔMoade4 mutant exhibiting adenine, adenosine, and hypoxanthine auxotrophy on MM. Conidia quantification assays showed ΔMoade4 mutant was significantly reduced in sporulation. The conidia of ΔMoade4 mutant could still form appressoria but mostly failed to penetrate the rice cuticle. Pathogenicity test showed ΔMoade4 was completely nonpathogenic on rice and barley leaves which was attributed by failure of its infectious hyphae to colonize the host cells. The ΔMoade4 was defective in induction of strong host immunity and had its purine transporter genes repressed during in planta infection. Addition of exogenous adenine partially rescued conidiation and pathogenicity defects of the ΔMoade4 mutant on the barley and rice leaves. Localization assays showed that MoAde4 is located in the cytoplasm. Taken together, our results demonstrate that purine biosynthesis orchestrated by MoAde4 is required for fungal development, conidiation, more importantly, we found it to be essential for fungal pathogenicity not because of the appressorial formation, but appressorium penetration and host colonization during the plant infection of M. oryzae. Thus this findings suggests that purine biosynthesis could act as an important target for combating recalcitrant plant fungal pathogens.

scholarly journals Cellular pyrimidine imbalance triggers mitochondrial DNA–dependent innate immunity

2021 ◽  
Author(s):  
Hans-Georg Sprenger ◽  
Thomas MacVicar ◽  
Amir Bahat ◽  
Kai Uwe Fiedler ◽  
Steffen Hermans ◽  
...  
Keyword(s):  
Mitochondrial Dna ◽  
Cultured Cells ◽  
De Novo ◽  
Metabolic Response ◽  
Interferon Response ◽  
Type I ◽  
Nucleotide Synthesis ◽  
Pyrimidine Synthesis ◽  
Pyrimidine Nucleotide ◽  
De Novo Pyrimidine Synthesis

AbstractCytosolic mitochondrial DNA (mtDNA) elicits a type I interferon response, but signals triggering the release of mtDNA from mitochondria remain enigmatic. Here, we show that mtDNA-dependent immune signalling via the cyclic GMP–AMP synthase‒stimulator of interferon genes‒TANK-binding kinase 1 (cGAS–STING–TBK1) pathway is under metabolic control and is induced by cellular pyrimidine deficiency. The mitochondrial protease YME1L preserves pyrimidine pools by supporting de novo nucleotide synthesis and by proteolysis of the pyrimidine nucleotide carrier SLC25A33. Deficiency of YME1L causes inflammation in mouse retinas and in cultured cells. It drives the release of mtDNA and a cGAS–STING–TBK1-dependent inflammatory response, which requires SLC25A33 and is suppressed upon replenishment of cellular pyrimidine pools. Overexpression of SLC25A33 is sufficient to induce immune signalling by mtDNA. Similarly, depletion of cytosolic nucleotides upon inhibition of de novo pyrimidine synthesis triggers mtDNA-dependent immune responses in wild-type cells. Our results thus identify mtDNA release and innate immune signalling as a metabolic response to cellular pyrimidine deficiencies.

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