N,S,Br co-doped carbon dots:One-step synthesis and fluorescent detection of 6-mercaptopurine in tablet

6-mercaptopurine(6-MP),a purine derivative(3,7-dihydropurine-6-thione),has been utilized as an effective immunosuppressive drug for clinically treating leukemia and other autoimmune diseases[1].6-MP and its corresponding metabolites can suppress the function of RnaseH,and thus they are cytotoxic and threaten the human health[2].Therefore,the accurate quantification of 6-MP is crucial.To date,researchers continue to expend considerable effort in developing 6-MP detection methods.Fluorescence analysis eliminates disadvantages,such as toxic solvents,expensive equipment.

Integrating UHPLC-MS/MS quantitative analysis and exogenous purine supplementation to elucidate the antidepressant mechanism of Chaigui granules by regulating purine metabolism

Chaigui granules(CG)are a compound composed of six herbal medicines with significant antidepressant effects.However,the antidepressant mechanism of CG remains unclear.In the present study,we attempted to elucidate the antidepressant mechanism of CG by regulating purine metabolism and purinergic signaling.First,the regulatory effect of CG on purine metabolites in the prefrontal cortex(PFC)of chronic unpredictable mild stress(CUMS)rats was analyzed by ultra high-performance liquid chromatography tandem mass spectrometry(UHPLC-MS/MS)targeted quantitative analysis.Meanwhile,purinergic receptors(P2X7 receptor(P2X7R),A1 receptor(A1R)and A2A receptor(A2AR))and signaling pathways(nod-like receptor protein 3(NLRP3)inflammasome pathway and cyclic adenosine monophosphate(cAMP)-protein kinase A(PKA)pathway)associated with purine metabolism were analyzed by western blotting and enzyme-linked immunosorbent assay(ELISA).Besides,antidepressant mechanism of CG by modulating purine metabolites to activate purinergic receptors and related signaling pathways was dissected by exogenous supplementation of purine metabolites and antagonism of purinergic receptors in vitro.An in vivo study showed that the decrease in xanthine and the increase in four purine nucleosides were closely related to the antidepressant effects of CG.Additionally,purinergic receptors(P2X7R,A1R and A2AR)and related signaling pathways(NLRP3 inflammasome pathway and cAMP-PKA pathway)were also significantly regulated by CG.The results of exogenous supplementation of purine metabolites and antagonism of purinergic receptors showed that excessive accumulation of xanthine led to activation of the P2X7R-NLRP3 inflammasome pathway,and the reduction of adenosine and inosine inhibited the A1R-cAMP-PKA pathway,which was significantly ameliorated by CG.Overall,CG could promote neuroprotection and ultimately play an antidepressant role by inhibiting the xanthine-P2X7R-NLRP3 inflammasome pathway and activating the adenosine/inosine-A1R-cAMP-PKA pathway.

Combinatorial co-expression of xanthine dehydrogenase and chaperone XdhC from Acinetobacter baumannii and Rhodobacter capsulatus and their applications in decreasing purine content in food

This study investigated the combinatorial expression of xanthine dehydrogenase(XDH)and chaperone XdhC from Acinetobacter baumannii and Rhodobacter capsulatus and their applications in decreasing purine content in the beer,beef and yeast.Naturally occurring xdhABC gene clusters of A.baumannii CICC 10254 and R.capsulatus CGMCC 1.3366 as well as two refactored clusters constructed by exchanging their xdhC genes were overexpressed in Escherichia coli and purified to near homogeneity.RcXDH chaperoned by AbXdhC showed nearly the same catalytic performance as that by RcXdhC,except for the decreased substrate affinity.While the AbXDH co-expressed with RcXdhC displayed enhanced acidic adaptation but weakened catalytic activity.All the XDHs degraded purines in beer,beef and yeast extract effectively,indicating potential applications in low-purine foods to prevent hyperuricemia and gout.The study also presents a method for exploiting the better chaperone XdhC and novel XDHs by functional complement activity using existing XdhCs such as RcXdhC.

Differential accumulation mechanisms of purine alkaloids and catechins in Camellia ptilophylla,a natural theobromine-rich tea

Tea is consumed worldwide due to its charming flavor and the refreshing effects conferred by caffeine.Caffeine however has undesirable side effects,such as sleep disturbance.Camellia ptilophylla is known for its low caffeine content,and the biosynthesis of purine alkaloids in this species has become a hot topic.In this study,the accumulation of purine alkaloids in a natural C.ptilophylla population(32 plants)was analyzed,and the results showed that 81.25%of this population were caffeine-free,containing only theobromine(TB),while six plants contained both theobromine and caffeine(CAF).RNA-seq analysis of two C.ptilophylla plants with contrasting purine alkaloid contents(TB and CAF)revealed that xanthosine synthesis genes of the SAM cycle and AMP pathway were significantly related to the differential accumulation of purine alkaloids between TB and CAF.The high theobromine content in TB was attributed to the significantly higher expression of TCS-2,TCS-3 and MXMTs and downregulation of the xanthosine degradation pathway in comparison to CAF.Additionally,CsMYB184 was significantly upregulated in TB,opposing the expression pattern of TCS1,but consistent with that of other TCSs and MXMTs.Furthermore,the upregulated expression of catechin biosynthesis genes,F3'H,F3'5'H and SCPLs in TB corresponded to a higher gallocatechin gallate(GCG)content.Overall,these findings provide new insights into the accumulation of theobromine and GCG,which may facilitate the development of tea plant cultivars with low-caffeine or high GCG to meet the diverse demands of consumers.

Separation of Purine and Its Derivatives by Capillary Zone Electrophoresis

The separation of a group of 17 purine and its derivatives by capillary zone electrophoresis is presented. A systematic approach was used to study the effect of pH, buffer type, organic modifiers, applied potential, sodium dodecyl sulfate (SDS) and cyclodextrins on the separation of these purine derivatives. An ideal condition was found for their separation, which was 30 mmol/L sodium borate buffer (pH 9–9.5), 10%(V/V) methanol buffer modifier and 20 kV. Under this condition, the 17 purine derivatives were baseline separated and the linear correlation coefficient for adenine, uric acid and 2-thioxanthine was 0. 99 over two orders of magnitude. The variation of peak areas was less than 4. 6%(n=5) and that of migration times was in the range of 0%–3%, while the samples were injected hydrodynamically at a height of 15 cm and an injection time of 8–10 s. In addition, alcohol, 1-propanol, 1-butanol and acetonitrile were also effective additives in the separation. However, SDS and various β-cyclodextrin (β-CDs) were found to do no good to their separation.

Evolutionary impacts of purine metabolism genes on mammalian oxidative stress adaptation

Many mammals risk damage from oxidative stress stemming from frequent dives(i.e., cycles of ischemia/reperfusion and hypoxia/reoxygenation),high altitude and subterranean environments, or powered flight. Purine metabolism is an essential response to oxidative stress, and an imbalance between purine salvage and de novo biosynthesis pathways can generate damaging reactive oxygen species(ROS). Here, we examined the evolution of 117 purine metabolism-related genes to explore the accompanying molecular mechanisms of enhanced purine metabolism in mammals under high oxidative stress. We found that positively selected genes,convergent changes, and nonparallel amino acid substitutions are possibly associated with adaptation to oxidative stress in mammals. In particular, the evolution of convergent genes with c AMP and c GMP regulation roles may protect mammals from oxidative damage. Additionally, 32 genes were identified as under positive selection in cetaceans, including key purine salvage enzymes(i.e., HPRT1), suggesting improved re-utilization of non-recyclable purines avoid hypoxanthine accumulation and reduce oxidative stress. Most intriguingly, we found that six unique substitutions in cetacean xanthine dehydrogenase(XDH), an enzyme that regulates the generation of the ROS precursor xanthine oxidase(XO) during ischemic/hypoxic conditions, show enhanced enzyme activity and thermal stability and diminished XO conversion activity. These functional adaptations are likely beneficial for cetaceans by reducing radical oxygen species production during diving. In summary, our findings offer insights into the molecular and functional evolution of purine metabolism genes in mammalian oxidative stress adaptations.

Purine nucleotides and their metabolites in patients with type 1 and 2 diabetes mellitus

We measured the erythrocyte levels of principal nucleotides (ATP, ADP, AMP, GTP, GDP, GMP, IMP), nucleosides (Ado, Guo, Ino) and Hyp with HPLC. Purine concentrations were determined in the erythrocytes of 36 type 1 and 40 type 2 diabetic patients. The increased dephosphorylation of adenine and guanine nucleotides, indicated by increased Ado, Ino, Guo and Hyp concentrations as the products of purine nucleotide degradation, suggests serious energy metabolism disruptions in diabetes. An increase in AMP, GMP, IMP concentrations, as well as a decrease in AEC and GEC values, points to significant alterations in erythrocyte purine nucleotide concentration.

Four New 6-Oxy Purine Alkaloids from the South China Sea Sponge,Haliclona cymaeformis

In this study, the chemical analysis of the marine sponge spieces, Haliclona cymaeformis, collected from the South China Sea was carried out, Two pairs of regioisomers of alkyl substitutional 6-oxy purine alkaloids(1a/1b and 2a/2b) were isolated. All of them possess two structural moieties, a 6-oxy purine nucleus and a pentan-2-one or hexan-2-one alkyl chain. Among them, 1a and 2a are the major N-9-substitutional regioisomers, and 1b and 2b are the minor N-7-substitutional regioisomers.

Silencing of Os XDH reveals the role of purine metabolism in dark tolerance in rice seedlings

Xanthine dehydrogenase(XDH) is a crucial enzyme involved in purine metabolism. To evaluate the effect of XDH deficiency on rice growth during dark treatment, wild type(WT) Nipponbare(Oryza sativa L.) and two independent transgenic lines with severe RNAi suppression(xdh3 and xdh4) were used in the present experiment. Under normal growth conditions, chlorophyll levels and biomass were indistinguishable between WT and the two RNAi transgenic lines, but XDH enzyme activity and ureide levels were suppressed in XDH RNAi transgenic lines. When XDH RNAi transgenic lines were subjected to dark treatment, chlorophyll content and biomass were significantly decreased, while O~–· production rate and malonaldehyde(MDA) were significantly increased compared to WT. The spraying test of exogenous allantoin raised chlorophyll content and biomass and reduced O~–· production rate and MDA in WT and both transgenic lines, and it also simultaneously reduced differences between RNAi and WT plants caused by XDH deficiency in growth potential and anti-oxidative capacity under dark treatment. These results suggested that fully functional purine metabolism plays an important role in reducing the sensitivity of rice seedlings to dark stress.

Tetra-n-butylammonium Hydroxide:an Efficient Catalyst for N-Alkylation of Pyrimidines and Purines

An efficient procedure for N-alkylation of pyrimidines and purines in the presence of tetra-n-butylammonium hydroxide（TBAH） is described. The method is very practical and the alkylation can occur at room temperature and the yields of the N-alkyl pyrimidines and purines were found to be excellent.

The Synthesis of Bridged Purine Dinucleoside

Two bridged purine dinucleosides, bis(2-N-acetyl-6-N-alkylylene-2,6-diaminopurine-2',3',5'-triacetyl-beta-D-ribofuranoside), were synthesized fi om the reaction of the key medium 3, 2-acetylamino-6-[1-(1,2,4-triazolyl)]-purine-2',3',5'-triacetyl-beta-D-ribofuranoside with dialkylamine.

CHANGES OF MONOAMINES, PURINES AND AMINO ACIDS IN RAT STRIATUM AS MEASURED BY INTERCEREBRAL MICRODIALYSIS DURING ISCHEMIA/REPERFUSION

The aim of this study was to determine the time course of changes in extracellular fluid (ECF) concentrations of purines, amino acids, monoamines, and their metabolites in the striatum of rats during ischemia and reperfusion, using intracerebral microdialysis as the sampling technique. In rats subjected to 20 min forebrain ischemia by four-vessel occlusion, the concentrations of adenosine (Ade), inosine (Ino) and hypoxanthine (Hyp) were found to rise markedly. These changes were accompanied by dramatically elevated levels of aspartate (Asp), glutamate (Glu), taurine (Tau), γ-aminobutyric acid (GABA), dopamine (DA) and norepinephrine (NE), all of which gradually returned to baseline following reperfusion. Concomitantly, the levels of metabolite 3, 4-dihydroxyphenylacetic acid (DOPAC) . homovanillic acid (HVA), 5-hydroxyindole-3-acetic acid (5-HIAA) and xanthine (Xan) decreased during ischemia and gradually recovered 60～ 90 min after reperfusion. It was concluded that during global brain ischemia, the ECF is flooded with both potentially harmful (e. g. Asp, Glu, DA) and protective (e. g. Tau, GABA, Ade) agents.

Structural Insight into the Binding of Hypoxanthine with Purine Nucleoside Phosphorylase from Streptococcus mutants

Purine nucleoside phosphorylase is a key enzyme in the purine-salvage pathway and an attractive target for drug design. The crystal structure of Streptococcus mutants purine nucleoside phosphorylase（Smu PNP） has been solved by molecular replacement at 1.80 resolution and refined to R factors of 19.9%/23.7%（Rcryst/Rfree） . Sequence alignment and structural comparison show that Smu PNP has more similarity with PNPs isolated from human and malarial sources than the bacterial PNPs. The structure complexed with hypoxanthine（HPA） and sulfate ion was solved at 2.24A resolution and refined to R factors of 21.6%/24.1%（Rcryst/Rfree） . It is interesting to note that the resulting electron density indicated the product,HPA,presents in the active site although inosine was included in the crystallization mixture with Smu PNP. Asn233 and Glu191 are the important residues for ligand binding and recognition. Comparison with PNPs from different species gives detailed information about binding of small molecules on the active site,which is important for the studies of enzymatic mechanism and rational design of specific inhibitors for PNPs.

Development and Validation of a Single HPLC Method for Analysis of Purines in Fish Oil Supplements

Gout is one of the most common forms of inflammatory arthritis, affecting over 8 million adults in the US. Individuals with gout are advised to avoid the habitual intake of purine-rich foods such as meats, seafood, purine-rich vegetables, and animal protein. An increased risk of developing or having subsequent attacks of gout is particularly associated with the consumption of seafood. However, clinical studies have shown that certain seafood and fish oil supplements that contain large amounts of omega-3 fatty acids provide important cardiovascular benefits. Individuals who might benefit from omega-3 fatty acid supplementation may therefore avoid fish oil products because they contain purines. Currently, there are no distinct high-performance liquid chromatography (HPLC) methods available in the literature that are validated as per the International Conference on Harmonisation (ICH) guidelines for the analysis of omega-3 fatty acid oils or fish oil containing products for purine content. A robust, fast, and efficient reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed and validated for the specific analysis of the naturally occurring purines guanine, purine, theobromine, and adenine. These purines are often found in fish oil and seafood. The analytical method reported herein quantifies all four purines in fish oil in about 20 minutes.

Bio-Medical Aspects of Purine Alkaloids

This review shortly summarized bio-medical activities of purine alkaloids, caffeine (caf), theophyline (top) and theobromine (tob). Caffeine potentiates the cytotoxicity of a variety of DNA domaging agents. Caffeine increased antitumor activity of some cancerostatic drugs. Caffeine inhibits the carcinogenic activity of cigarette smoke, significantly potentiating the therapeutic effect of acetaminophenol, cyclophosphoramide, enhances lipid oxidation, affects the central nervous system and alters cardiovascular system. Theophyline has expressive anti-inflammatory and antiasthmatic effect, and enhanced mobilization of lipid reduces the brain regional adenylate cyclase activity, facilitates glucose inhibition. Theophyline is muscle relaxant, vasodilator, diuretic and cardiac stimulant. Theobromine increases antitumor activity of adriamycin and doxorubicin, has expressive anti-inflammatory effect and it is classical diureticum. Several examples of caffeine with some organic substrates as well as with copper are also outlined. Increasing activity of the respective drugs in the present of the purine alkaloids can be ascribed to direct interaction as was proved by X-ray data of some caffeine adducts with organic substances as well as Cu(II) complexes.

Synthesis of Novel 4-Thiazolidinone and Bis-Thiazalidin-4-One Derivatives Derived from 4-Amino-Antipyrine and Evaluated as Inhibition of Purine Metabolism Enzymes by Bacteria

Novel 4-thiazolidione and 1,4-bis-thiazolidinone derivatives bearing antipyrine moiety have been obtained from condensation of 4-aminoantipyrine 1 with aromatic/heteroaldehydes followed by cycloaddition with mercaptoacetic acid in nonpolar solvents. Structure of the products has been deduced upon their elemental analysis and spectral measurements. Most of the targets evaluated as enzymatic effect towards some bacteria (E. coli) in compare with Xanthine oxidase (from buttermilk) where the role of compounds is an inhibition of purine metabolism enzymes caused by E. coli.

Case of purine nucleoside phosphorylase deficiency presented with hematuria

Purine Nucleoside Phosphorylase (PNP) deficiency is a rare autosomal recessive metabolic disorder. In PNP-deficiency disorder, the deficient enzyme leads to accumulation of toxic metabolites, especially in lymphocytes and the metabolites exert toxic effect on T-cell generation. Purine nucleoside phosphorylase deficiency causes decreased numbers of T cells and lymphopenia. The patients suffering from PNP-deficiency may be admitted with recurrent infections, as well as neurological and autoimmune findings. We hereby presented a case admitted with the symptom of hematuria in which we established the diagnosis of PNP-deficiency early on the basis of detection of lymphopenia and low level of uric acid.

Methylthioadenosine (MTA) Rescues Methylthioadenosine Phosphorylase (MTAP)-Deficient Tumors from Purine Synthesis Inhibition <i>in Vivo</i>via Non-Autonomous Adenine Supply

Methylthioadenosine phosphorylase, (MTAP) is a key enzyme in the adenine and methionine salvage pathways. MTAP is encoded on human chromosome 9p21 in close proximity to the p16INK4a and p14ARF tumor suppressor genes and is frequently co-deleted with p16INK4a in many cancers. Deletion of MTAP has been reported to create a reliance of MTAP–/– tumors on de novo purine synthesis to maintain adequate pools of AMP, leading to increased sensitivity to purine synthesis inhibitors, such as L-alanosine. The ‘Achilles heel’ created by the loss of MTAP in cancer cells provides a unique therapeutic opportunity whereby MTAP–/– tumors could be selectively targeted with purine synthesis inhibitors and normal tissues could be preferentially rescued with MTAP substrates, such as MTA. We demonstrate that, in contrast to published literature, MTAP–/– cells are not more sensitive to inhibition of de novo purine synthesis than MTAP+/+ cells. Although MTA can preferentially rescue MTAP+/+ cells from purine-synthesis inhibitor toxicity in vitro, MTA protects cells of both genotypes from L-alanosine equivalently in vivo. Our data demonstrate that in vivo, adenine salvaged from plasma and adjacent tissues is sufficient to protect MTAP–/– tumors from the effects of purine synthesis inhibitors. These results suggest targeting MTAP–/– tumors with de novo purine synthesis inhibitors is unlikely to provide significant benefit over other therapeutic strategies and may explain, at least in part, the lack of efficacy of L-alanosine in clinical trials.

Purine and Pyrimidine-Linked Enzymes and Genes are Strongly Responsible for the Development of Tumors, Particularly Glioblastoma Multiforme

We were aiming to delineate, by the utility of the biological data results, in our investigations the link between the purine and pyrimidine metabolism and development of the glioblastoma. We analyzed the sets of the genes, belonging to the purine and pyrimidine metabolism by the utility of GSEA software as well as MSIgnDB application of the GSEA. The GEO database, GEOR2 tools were serving for the visualization of the genes expression profiles of the disease. The Cancer Proteome Atlas as well as the tools of the data sets were also used to collect and analyze the results. We concluded and came to the following consequential results. 1) Neurogenesis and Glioblastoma are sharing some common genes. 2) Purine and pyrimidine metabolism-linked enzymes and genes are responsible for the upregulation of DNA and mRNA synthesis in the settings of the tumor development. 3) EGFR expression responsible genes, mRNA as well as protein is upregulated during the development of the glioblastoma. 4) GMPS genes are more strongly upregulated in the settings of the glioblastoma than ADSL. 5) PRPS1 is strongly synthetized in neurospheres in contrast to the mature tissue during glioblastoma development.

Dietary ribose supplementation improves flesh quality through purine metabolism in gibel carp(Carassius auratus gibelio)

Since the aquaculture industry is currently observing a deterioration in the flesh quality of farmed fish,the use of nutrients as additives to improve the flesh quality of farmed fish species is a viable strategy.The aim of this study was to investigate the effect of dietary D-ribose(RI)on the nutritional value,texture and flavour of gibel carp(Carassius auratus gibelio).Four diets were formulated containing exogenous RI at 4 gradient levels:0(Control),0.15%(0.15RI),0.30%(0.30RI)and 0.45%(0.45RI).A total of 240 fish(150±0.31 g)were randomly distributed into 12 fibreglass tanks(150 L per tank).Triplicate tanks were randomly assigned to each diet.The feeding trial was carried out in an indoor recirculating aquaculture system for 60 d.After the feeding trial,the muscle and liver of gibel carp were analysed.The results showed that RI supplementation did not result in any negative impact on the growth performance and 0.30RI supplementation significantly increased the whole-body protein content compared to the control group.The contents of collagen and glycogen in muscle were enhanced by RI supplementation.The alterations in the flesh indicated that RI supplementation improved the texture of the flesh in terms of its water-holding capacity and hardness,therefore improving the taste.Dietary RI facilitated the deposition of amino acids and fatty acids in the muscle that contributed to the meaty taste and nutritional value.Furthermore,a combination of metabolomics and expression of key genes in liver and muscle revealed that 0.30RI activated the purine metabolism pathways by supplementing the substrate for nucleotide synthesis and thereby promoting the deposition of flavour substance in flesh.This study offers a new approach for providing healthy,nutritious and flavourful aquatic products.