guanosine-monophosphate and purine

The focus of this review is the human de novo purine biosynthetic pathway. The pathway enzymes are enumerated, as well as the reactions they catalyze and their physical properties. Early literature evidence suggested that they might assemble into a multi-enzyme complex called a metabolon. The finding that fluorescently-tagged chimeras of the pathway enzymes form discrete puncta, now called purinosomes, is further elaborated in this review to include: a discussion of their assembly; the role of ancillary proteins; their locus at the microtubule/mitochondria interface; the elucidation that at endogenous levels, purinosomes function to channel intermediates from phosphoribosyl pyrophosphate to AMP and GMP; and the evidence for the purinosomes to exist as a protein condensate. The review concludes with a consideration of probable signaling pathways that might promote the assembly and disassembly of the purinosome, in particular the identification of candidate kinases given the extensive phosphorylation of the enzymes. These collective findings substantiate our current view of the de novo purine biosynthetic metabolon whose properties will be representative of how other metabolic pathways might be organized for their function.

Topics: Adenosine Monophosphate; Biosynthetic Pathways; Cyclic AMP; Cyclic GMP; Guanosine Monophosphate; Humans; Microtubules; Mitochondria; Multienzyme Complexes; Phosphoribosyl Pyrophosphate; Phosphorylation; Proteins; Purines; Signal Transduction

Topics: Animals; Arthritis, Rheumatoid; Depression, Chemical; Guanosine Monophosphate; Humans; Immunosuppressive Agents; Lupus Nephritis; Lymphocyte Activation; Mice; Purines; Randomized Controlled Trials as Topic; Ribonucleosides; Sjogren's Syndrome; T-Lymphocytes

Mycophenolate mofetil (MMF, CellCept), a semisynthetic derivative of mycophenolic acid (MPA) produced by a fungus, is an inhibitor of the inosine monophosphate dehydrogenase (IMPDH) enzyme (IC50 = 25 nM) that catalyzes the synthesis of guanosine monophosphate (GMP) from inosine. GMP is an essential nucleoside for purine synthesis during cell division. As T and B-lymphocytes almost exclusively use the de novo pathway of purine synthesis, these cells are particularly sensitive to the inhibitory action of MMF. It has a mechanism of action distinct from cyclosporine and tacrolimus. Although MMF does not affect cytokine production, by inhibiting the rate-limiting enzyme IMPDH in the de novo synthesis of purines, it inhibits the proliferation of T and B-lymphocytes, the production of antibodies, and the generation of cytotoxic T lymphocytes. Reversal of acute allograft rejection and increased survival of kidney, heart and bone marrow cell allograft has been shown in several animal studies. Moreover, it was suggested that MMF combined with CsA prevented the acute rejection, and approximately half of the animals became long-term survivors. The Ministry of Health and Welfare approved MMF in 1999 for use for rejection treatment in renal transplantation based on several prospective, randomized and blind efficacy trials.

Topics: Animals; Enzyme Inhibitors; Graft Rejection; Guanosine Monophosphate; Humans; Immunosuppressive Agents; IMP Dehydrogenase; Kidney Transplantation; Lymphocytes; Mycophenolic Acid; Prodrugs; Purines; Randomized Controlled Trials as Topic

Acute kidney injury (AKI) is common in patients hospitalized for COVID-19, complicating their clinical course and contributing to worse outcomes. Animal studies show that adenosine, inosine and guanosine protect the kidney against some types of AKI. However, until now there was no evidence in patients supporting the possibility that abnormally low kidney levels of adenosine, inosine and guanosine contribute to AKI. Here, we addressed the question as to whether these renoprotective purines are altered in the urine of COVID-19 patients with AKI. Purines were measured by employing ultra-high-performance liquid chromatography-tandem mass spectrometry with stable-isotope-labeled internal standards for each purine of interest. Compared with COVID-19 patients without AKI (n = 23), COVID-19 patients with AKI (n = 20) had significantly lower urine levels of adenosine (P < 0.0001), inosine (P = 0.0008), and guanosine (P = 0.0008) (medians reduced by 85%, 48% and 61%, respectively) and lower levels (P = 0.0003; median reduced by 67%) of the 2nd messenger for A

Topics: Acute Kidney Injury; Adenosine; Adenosine Monophosphate; Animals; COVID-19; Guanosine; Guanosine Monophosphate; Inosine; Purines

Meat quality attributes vary with chicken age. Understanding the relationship between poultry age and the quality of the meat would be beneficial for efficient poultry farming to meet market needs. The Korat hybrid chicken (KC) is a new crossbred chicken whose meat quality is distinct from that of commercial broiler (CB) chickens and has not been well characterized. In this study, we characterized the physico-chemical properties of KC meat and correlate the findings with Raman spectral data. The protein content of KC breast and thigh meat increased with age. The pH of thigh meat decreased, while the water-holding capacity of breast meat increased as the age of the chickens increased. The amount of cholesterol in breast meat decreased as the rearing period was extended. Inosine 5'-monophosphate and guanosine 5'-monophosphate of breast meat decreased as KC grew older. The shear force values of meat from older birds increased concomitantly with an increase in total collagen. Principle component analysis revealed that the meat quality of CB was greatly different from that of KC meat. High shear force values of KC meat at 20 wk of age were well correlated with an increase in the β-sheet structure (amide I) and amide III of collagen. Raman spectra at 3,207 cm

Topics: Age Factors; Animals; Chickens; Cholesterol; Collagen; Fatty Acids; Fourier Analysis; Guanosine Monophosphate; Hydrogen-Ion Concentration; Inosine Monophosphate; Meat; Proteins; Purines; Shear Strength; Spectrum Analysis, Raman

Brain tumor initiating cells (BTICs), also known as cancer stem cells, hijack high-affinity glucose uptake active normally in neurons to maintain energy demands. Here we link metabolic dysregulation in human BTICs to a nexus between MYC and de novo purine synthesis, mediating glucose-sustained anabolic metabolism. Inhibiting purine synthesis abrogated BTIC growth, self-renewal and in vivo tumor formation by depleting intracellular pools of purine nucleotides, supporting purine synthesis as a potential therapeutic point of fragility. In contrast, differentiated glioma cells were unaffected by the targeting of purine biosynthetic enzymes, suggesting selective dependence of BTICs. MYC coordinated the control of purine synthetic enzymes, supporting its role in metabolic reprogramming. Elevated expression of purine synthetic enzymes correlated with poor prognosis in glioblastoma patients. Collectively, our results suggest that stem-like glioma cells reprogram their metabolism to self-renew and fuel the tumor hierarchy, revealing potential BTIC cancer dependencies amenable to targeted therapy.

Topics: Adenosine Monophosphate; Cell Proliferation; Cells, Cultured; Genomics; Glioma; Glycolysis; Guanosine Monophosphate; Humans; Metabolomics; Neoplastic Stem Cells; Proto-Oncogene Proteins c-myc; Purines; Ribose-Phosphate Pyrophosphokinase; Up-Regulation

Purine acquisition is an essential nutritional process for Leishmania. Although purine salvage into adenylate nucleotides has been investigated in detail, little attention has been focused on the guanylate branch of the purine pathway. To characterize guanylate nucleotide metabolism in Leishmania and create a cell culture model in which the pathways for adenylate and guanylate nucleotide synthesis can be genetically uncoupled for functional studies in intact cells, we created and characterized null mutants of L. donovani that were deficient in either GMP reductase alone (Δgmpr) or in both GMP reductase and its paralog IMP dehydrogenase (Δgmpr/Δimpdh). Whereas wild type parasites were capable of utilizing virtually any purine nucleobase/nucleoside, the Δgmpr and Δgmpr/Δimpdh null lines exhibited highly restricted growth phenotypes. The Δgmpr single mutant could not grow in xanthine, guanine, or their corresponding nucleosides, while no purine on its own could support the growth of Δgmpr/Δimpdh cells. Permissive growth conditions for the Δgmpr/Δimpdh necessitated both xanthine, guanine, or the corresponding nucleosides, and additionally, a second purine that could serve as a source for adenylate nucleotide synthesis. Interestingly, GMPR, like its paralog IMPDH, is compartmentalized to the leishmanial glycosome, a process mediated by its COOH-terminal peroxisomal targeting signal. The restricted growth phenotypes displayed by the L. donovani Δgmpr and Δgmpr/Δimpdh null mutants confirms the importance of GMPR in the purine interconversion processes of this parasite.

Topics: Adenosine Monophosphate; Gene Knockdown Techniques; Genotype; GMP Reductase; Guanosine Monophosphate; IMP Dehydrogenase; Leishmania donovani; Mutation; Phenotype; Protein Transport; Purines; RNA Interference

Eukaryotic cells encode AMP-lysine (AMP-N-epsilon-(N-alpha-acetyl lysine methyl ester) 5'-phosphoramidate) hydrolases related to the rabbit histidine triad nucleotide-binding protein 1 (Hint1) sequence. Bacterial and archaeal cells have Hint homologs annotated in a variety of ways, but the enzymes have not been characterized, nor have phenotypes been described due to loss of enzymatic activity. We developed a quantitative (31)P NMR assay to determine whether Escherichia coli possesses an adenosine phosphoramidase activity. Indeed, soluble lysates prepared from wild-type laboratory E. coli exhibited activity on the model substrate adenosine 5'-monophosphoramidate (AMP-NH(2)). The E. coli Hint homolog, which had been comprehensively designated ycfF and is here named hinT, was cloned, overexpressed, purified, and characterized with respect to purine nucleoside phosphoramidate substrates. Bacterial hinT was several times more active than human or rabbit Hint1 on five model substrates. In addition, bacterial and mammalian enzymes preferred guanosine versus adenosine phosphoramidates as substrates. Analysis of the lysates from a constructed hinT knock-out strain of E. coli demonstrated that all of the cellular purine nucleoside phosphoramidase activity is due to hinT. Physiological analysis of this mutant revealed that the loss of hinT results in failure to grow in media containing 0.75 m KCl, 0.9 m NaCl, 0.5 m NaOAc, or 10 mm MnCl(2). Thus, cation-resistant bacterial cell growth may be dependent on the hydrolysis of adenylylated and/or guanylylated phosphoramidate substrates by hinT.

Topics: Adenosine Monophosphate; Animals; Cell Proliferation; Escherichia coli; Guanosine; Guanosine Monophosphate; Humans; Hydrolases; Hydrolysis; Lysine; Magnetic Resonance Spectroscopy; Models, Chemical; Mutation; Plasmids; Protein Conformation; Purine Nucleosides; Purines; Rabbits; Recombinant Proteins; Salts; Substrate Specificity; Time Factors; Transgenes

The structure of the purine regulon was studied by a comparative genomic approach in seven genomes of gamma-proteobacteria: Escherichia coli, Salmonella typhi, Yersinia pestis, Haemophilus influenzae, Pasteurella multocida, Actinobacillus actinomycetemcomitans, and Vibrio cholerae. The palindromic binding site of the purine repressor (consensus ACGCAAACGTTTGCGT) is fairly well retained of genes encoding enzymes that participate in the synthesis of inosinemonophosphate from phosphoribozylpyrophosphate and in transfer of unicarbon groups, and also upstream of some transport protein genes. These genes may be regarded as the main part of the purine regulon. In terms of physiology, the regulation of the purC and gcvTHP/folD genes seems to be especially important, because the PurR site was found upstream of nonorthologous but functionally replaceable genes. However, the PurR site is poorly retained in front of orthologs of some genes belonging to the E. coli purine regulon, such as genes involved in general nitrogen metabolism, biosynthesis of pyrimidines, and synthesis of AMP and GMP from IMP, and also upstream of the purine repressor gene. It is predicted that purine regulons of the examined bacteria include the following genes: upp participating in synthesis of pyrimidines; uraA encoding an uracil transporter gene; serA involved in serine biosynthesis; folD responsible for the conversion of N5,N10-methenyl tetrahydrofolate into N10-formyltetrahydrofolate; rpiA involved in ribose metabolism; and protein genes with an unknown function (yhhQ and ydiK). The PurR site was shown to have different structure in different genomes. Thus, the tendency for a decline of the conservatism of site positions 2 and 15 was observed in genomes of bacteria belonging to the Pasteurellaceae and Vibrionaceae groups.

Topics: Adenosine Monophosphate; Bacterial Proteins; Carbohydrate Dehydrogenases; Escherichia coli Proteins; Gammaproteobacteria; Gene Expression Regulation, Bacterial; Genomics; Guanosine Monophosphate; Inosine Monophosphate; Membrane Transport Proteins; Peptide Synthases; Phosphoglycerate Dehydrogenase; Purines; Pyrimidines; Regulon; Repressor Proteins; Serine; Tetrahydrofolates

Topics: Guanine; Guanosine; Guanosine Monophosphate; Nerve Growth Factors; Neurospora; Purines; Xanthine; Xanthines