Bioinformatic Analysis of <i>Helicobacter pylori</i> XGPRTase: A Potential Therapeutic Target

Duckworth, Megan J; Ménard, Armelle; Mégraud, Françis; Mendz, George L.

doi:10.1111/j.1523-5378.2006.00409.x

Cited by 9 publications

(9 citation statements)

References 42 publications

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“…These observations corroborate predictions made from the RAST-annotated H. pylori genomes, which all lack the pathway for de novo IMP synthesis [6]. H. pylori therefore relies on a purine salvage pathway (Figure 1), which has been partially characterized already [5], [7], [8]. Although several different strains were used for these prior studies, the gene homologs for purine salvage are well-conserved among the sequenced strains of H. pylori , making it likely that purine utilization is similar across strains [6].…”

Section: Introductionsupporting

confidence: 84%

Efficiency of Purine Utilization by Helicobacter pylori: Roles for Adenosine Deaminase and a NupC Homolog

2012

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The ability to synthesize and salvage purines is crucial for colonization by a variety of human bacterial pathogens. Helicobacter pylori colonizes the gastric epithelium of humans, yet its specific purine requirements are poorly understood, and the transport mechanisms underlying purine uptake remain unknown. Using a fully defined synthetic growth medium, we determined that H. pylori 26695 possesses a complete salvage pathway that allows for growth on any biological purine nucleobase or nucleoside with the exception of xanthosine. Doubling times in this medium varied between 7 and 14 hours depending on the purine source, with hypoxanthine, inosine and adenosine representing the purines utilized most efficiently for growth. The ability to grow on adenine or adenosine was studied using enzyme assays, revealing deamination of adenosine but not adenine by H. pylori 26695 cell lysates. Using mutant analysis we show that a strain lacking the gene encoding a NupC homolog (HP1180) was growth-retarded in a defined medium supplemented with certain purines. This strain was attenuated for uptake of radiolabeled adenosine, guanosine, and inosine, showing a role for this transporter in uptake of purine nucleosides. Deletion of the GMP biosynthesis gene guaA had no discernible effect on mouse stomach colonization, in contrast to findings in numerous bacterial pathogens. In this study we define a more comprehensive model for purine acquisition and salvage in H. pylori that includes purine uptake by a NupC homolog and catabolism of adenosine via adenosine deaminase.

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Section: Introductionsupporting

confidence: 84%

Efficiency of Purine Utilization by Helicobacter pylori: Roles for Adenosine Deaminase and a NupC Homolog

2012

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“…The susceptibility of H. pylori to C91 was assessed in Brucella broth, a nutrient rich medium that contains purines. This bacteria does contain a gene encoding a likely hypoxanthine-guanine phosphoribosyltransferase [73, 74], although the literature is conflicting with respect to the ability of H. pylori to salvage guanine [75, 76]. H. pylori will be resistant to IMPDH inhibitors if this salvage pathway can provide sufficient guanine nucleotides to support proliferation, so these assay conditions provide a demanding test for the antibiotic potential of IMPDH-targeted inhibitors.…”

Section: Inhibition Of H Pylori Growthmentioning

confidence: 99%

The Antibiotic Potential of Prokaryotic IMP Dehydrogenase Inhibitors

Hedstrom

Liechti²,

Goldberg³

et al. 2011

CMC

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Inosine 5′-monophosphate dehydrogenase (IMPDH) catalyzes the first committed step of guanosine 5′-monophosphate (GMP) biosynthesis, and thus regulates the guanine nucleotide pool, which in turn governs proliferation. Human IMPDHs are validated targets for immunosuppressive, antiviral and anticancer drugs, but as yet microbial IMPDHs have not been exploited in antimicrobial chemotherapy. Selective inhibitors of IMPDH from Cryptosporidium parvum have recently been discovered that display anti-parasitic activity in cell culture models of infection. X-ray crystal structure and mutagenesis experiments identified the structural features that determine inhibitor susceptibility. These features are found in IMPDHs from a wide variety of pathogenic bacteria, including select agents and multiply drug resistant strains. A second generation inhibitor displays antibacterial activity against Helicobacter pylori, demonstrating the antibiotic potential of IMPDH inhibitors.

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“…Similarly, the purine salvage pathway has also been investigated in numerous organisms (42,55). PRTases, the enzymes capable of joining salvaged purine bases with PRPP in order to generate purine nucleotides, have also been studied in numerous pathogens (17,18,38,39).…”

mentioning

confidence: 99%

“…Radiolabeling studies have been used to show uptake and incorporation of the purine bases adenine and guanine (and to a lesser extent, hypoxanthine) (50). The presence of adenine, guanine, and hypoxanthine phosphoribosyltransferase activities have been measured from whole-cell lysates (50), and an in-depth look at the enzymatic nature of H. pylori's purified xanthine-guanine phosphoribosyltransferase demonstrated its ability to catalyze the formation of 6-oxopurines (18). One study has shown that H. pylori can grow in the absence of preformed purines as long as exogenous catalase is present (49).…”

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confidence: 99%

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Helicobacter pylori Relies Primarily on the Purine Salvage Pathway for Purine Nucleotide Biosynthesis

Liechti

Goldberg

2012

J Bacteriol

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Helicobacter pylori is a chronic colonizer of the gastric epithelium and plays a major role in the development of gastritis, peptic ulcer disease, and gastric cancer. In its coevolution with humans, the streamlining of the H. pylori genome has resulted in a significant reduction in metabolic pathways, one being purine nucleotide biosynthesis. Bioinformatic analysis has revealed that H. pylori lacks the enzymatic machinery for de novo production of IMP, the first purine nucleotide formed during GTP and ATP biosynthesis. This suggests that H. pylori must rely heavily on salvage of purines from the environment. In this study, we deleted several genes putatively involved in purine salvage and processing. The growth and survival of these mutants were analyzed in both nutrient-rich and minimal media, and the results confirmed the presence of a robust purine salvage pathway in H. pylori. Of the two phosphoribosyltransferase genes found in the H. pylori genome, only gpt appears to be essential, and an ⌬apt mutant strain was still capable of growth on adenine, suggesting that adenine processing via Apt is not essential. Deletion of the putative nucleoside phosphorylase gene deoD resulted in an inability of H. pylori to grow on purine nucleosides or the purine base adenine. Our results suggest a purine requirement for growth of H. pylori in standard media, indicating that H. pylori possesses the ability to utilize purines and nucleosides from the environment in the absence of a de novo purine nucleotide biosynthesis pathway. Helicobacter pylori is a Gram-negative, microaerophilic helixshaped bacterium that colonizes the gastric mucosa of roughly half of the world's population (19,53). Unlike numerous other pathogenic bacteria capable of existing in diverse environmental niches, H. pylori is only capable of sustained growth within its human host (19). Identified only 27 years ago (45), this bacterium was the first to have two different strains sequenced, allowing for the first genome-wide comparative bioinformatic analysis of a bacterial species (1, 16). The results of this comparative sequencing project (16) as well as subsequent sequencing projects (3) show a relatively small genome with numerous alterations in its metabolic pathways compared with those of other bacterial species. Initial conclusions were that the missing pathway enzymes simply were divergent enough to escape classification by homology screening (16); however, subsequent analysis of the genome has identified 48 potential "dead-end metabolites" (metabolites only consumed or only produced within a metabolic network), indicating missing knowledge about a particular pathway or absence of a fully functional pathway (67). One hypothesis developed to explain these abnormalities was that, having evolved alongside humans for so long, the metabolism of H. pylori was streamlined to coexist in the human niche. Apparent holes in the metabolic pathways of H. pylori suggest the loss of genes no longer required for growth in its relatively stable environment of the huma...

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Bioinformatic Analysis of Helicobacter pylori XGPRTase: A Potential Therapeutic Target

Cited by 9 publications

References 42 publications

Efficiency of Purine Utilization by Helicobacter pylori: Roles for Adenosine Deaminase and a NupC Homolog

Efficiency of Purine Utilization by Helicobacter pylori: Roles for Adenosine Deaminase and a NupC Homolog

The Antibiotic Potential of Prokaryotic IMP Dehydrogenase Inhibitors

Helicobacter pylori Relies Primarily on the Purine Salvage Pathway for Purine Nucleotide Biosynthesis

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