Purine metabolism in Neisseria gonorrhoeae: the requirement for hypoxanthine

1980 ◽  
Vol 26 (1) ◽  
pp. 13-20 ◽  
Author(s):  
Stephen A. Morse ◽  
Lynne Bartenstein
Keyword(s):  
Neisseria Gonorrhoeae ◽  
Growth Medium ◽  
De Novo ◽  
Defined Medium ◽  
Purine Metabolism ◽  
Purine Biosynthesis ◽  
Free Medium ◽  
De Novo Purine Biosynthesis ◽  
Reduced Rate

Strains isolated from disseminated gonococcal infections often require hypoxanthine for growth. The biochemical bases for the requirement for hypoxanthine in strains isolated from both disseminated (Ile−Val−Arg−Hyx−Ura−phenotype) and non-disseminated (Hyx−phenotype) infections were compared. The requirement for hypoxanthine was dependent upon the composition of the growth medium. In a complete defined medium, hypoxanthine was replaced by a mixture of adenine and guanine but not by either purine alone. The addition of adenine alone inhibited gonococcal growth. This inhibition was reversed by the addition of guanine and most likely resulted from an inhibition of de novo purine biosynthesis. In a histidine-free medium, adenine replaced the hypoxanthine requirement in Ile−Val−Arg−Hyx−Ura− strains. Adenine did not replace the hypoxanthine requirement in Hyx− strains. The Ile−Val−Arg−Hyx−Ura− strains exhibited a markedly reduced rate of de novo purine biosynthesis while Hyx− strains were blocked in this pathway. In vivo concentrations of purines are important factors which may limit the intracellular or extracellular growth of these strains.

scholarly journals EXTH-40. THERAPEUTICALLY TARGETING DE NOVO PURINE BIOSYNTHESIS IN DIFFUSE INTRINSIC PONTINE GLIOMA

2020 ◽  
Vol 22 (Supplement_2) ◽  
pp. ii95-ii96
Author(s):  
Ian Mersich ◽  
Biplab Dasgupta
Keyword(s):  
Overall Survival ◽  
Cell Lines ◽  
De Novo ◽  
Diffuse Intrinsic Pontine Glioma ◽  
Purine Metabolism ◽  
Purine Biosynthesis ◽  
Therapeutic Window ◽  
Pontine Glioma ◽  
Genetic Ablation ◽  
De Novo Purine Biosynthesis

Abstract Diffuse intrinsic pontine glioma (DIPG) is an incurable brainstem malignancy in children with median survival less than 1 year and 5-year overall survival only 2 percent. Little progress has been made in treating this deadly disease due to its inoperable location and treatments aimed at targets defined in adult gliomas. Despite recent advances in genetic characterization of DIPGs there are still no targeted therapies that significantly improve overall survival. We recently generated a metabolic profile for DIPG elucidating an upregulation in purine metabolism, specifically in de novo purine biosynthesis (DNPB). Normally nucleotide salvage maintains cellular purine levels by recycling degraded bases, however DNPB is needed when purine levels are depleted. Purine metabolism provides the basic components of nucleotides needed for tumor proliferation and thus considered a high-priority target in cancer treatment. DNPB is a sequential ten step enzymatic process resulting in the production of inosine monophosphate. The last step in DNPB is carried out by the bifunctional enzyme ATIC which is upregulated in DIPG cell lines, and in patient tumors. Our preliminary data demonstrates DIPG cell lines are sensitive to pharmacological inhibition and genetic ablation of multiple enzymes in the DNPB pathway. Strikingly, cell viability could be rescued by purine supplementation when inhibiting this pathway except when ATIC is inhibited indicating the mechanism of cell death for ATIC inhibition is independent of purine nucleotide levels. Furthermore, there is a therapeutic window for targeting ATIC in DIPG cell lines relative to normal neural stem cells and normal human astrocytes. Metabolic flux experiments have demonstrated DNPB is upregulated in DIPG cell lines and the reason these cells are more sensitive to ATIC inhibition is likely related to the rapid accumulation of a cytotoxic metabolite upstream of ATIC. In vivo studies are currently underway in pre-clinical mouse models for DIPG.

scholarly journals OS6.1 Targeting Purine Metabolism to Overcome Therapeutic Resistance in Glioblastoma

2019 ◽  
Vol 21 (Supplement_3) ◽  
pp. iii12-iii12
Author(s):  
A U Ahmed ◽  
J Shireman ◽  
F Atashi ◽  
M Saathoff ◽  
E Ali ◽  
...  
Keyword(s):  
De Novo ◽  
Interaction Analysis ◽  
Building Blocks ◽  
Purine Biosynthesis ◽  
P Value ◽  
Inosine Monophosphate Dehydrogenase ◽  
Salvage Pathway ◽  
Pathway Activity ◽  
De Novo Purine Biosynthesis

Abstract BACKGROUND A distinguishing characteristic of all cancers is uncontrolled cell division, and they require additional nucleotide bases such as purines, the building blocks of DNA and RNA, to sustain their uncontrolled growth. Purines can be synthesized from scratch by de novo pathway or salvaged by recycling surrounding nucleotides that are released by hydrolytic degradation. Even though the central nervous system (CNS), as well as CNS associated malignancies like glioblastoma (GBM), rely more heavily on the salvage pathway due to its energy efficiency, its precious role in promoting chemoresistance and GBM recurrence is yet to be elucidated. MATERIAL AND METHODS We have examined the role of purine biosynthesis in GBM by using stable isotope tracing analysis as well as utilizing a knockdown (KD) system to investigate its effect on i) DNA damage response during temozolomide (TMZ) therapy, ii) tumor engraftment and iii) therapeutic responses in vivo. RESULTS Through gene expression and protein-protein interaction analysis, we have identified ARL13B, member of ADP-ribosylation factor-like protein family, as a novel regulator of the purine biosynthesis pathway in GBM. ARL13B can physically interacting with the inosine monophosphate dehydrogenase 2 (IMPDH2), a key rate-limiting enzyme for purine biogenesis. Isotope tracer analysis under normal physiological conditions revealed that during TMZ treatment, salvage recycling activity was decreased by 50% while de novo pathway activity remains unchanged. In contrast, TMZ treatment of ARL13B knock-out cells results in a ~50% decrease in de novo pathway activity (p-value=0.004), whereas purine salvage pathway activity is upregulated ~6-fold (p-value <0.0001). ARL13B knockdown cells treated with TMZ show a robust increase in DNA double-strand breaks compared to control cells exposed to TMZ, as demonstrated by gH2X staining. Mice orthotopically engrafted with KD cells experience prolonged survival relative to mice engrafted with unmodified cells. CONCLUSION We propose that ARL13B-IMPDH2 interaction has two consequences: i) augmentation of de novo purine biosynthesis activity, and ii) inhibition of nucleotide recycling. The increasing de novo purine biosynthesis during TMZ therapy helps GBM cells reduce the recycling of nucleotides via the salvage pathway that have been modified as a result of TMZ alkylation. This, in turn, protects the cells from deleterious effects of incorporating modified nucleotides into newly-synthesized DNA while maintaining a supply of purine building blocks to support uncontrolled proliferation. Our results indicate that the interaction of ARL13B-IMPDH2 functions as a purine biosynthesis regulator that could be targeted for increasing efficacy of TMZ treatment of GBM. ​

scholarly journals Carbocyclic substrates for de novo purine biosynthesis.

1991 ◽  
Vol 266 (25) ◽  
pp. 16699-16702
Author(s):  
D.S. Liu ◽  
C.A. Caperelli
Keyword(s):  
De Novo ◽  
Purine Biosynthesis ◽  
De Novo Purine Biosynthesis
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