scholarly journals Metabolism of xanthine and hypoxanthine in the tea plant (Thea sinensis L.)

1975 ◽  
Vol 146 (1) ◽  
pp. 79-85 ◽  
Author(s):  
T Suzuki ◽  
E Takahashi
Keyword(s):  
De Novo ◽  
Tea Plant ◽  
Shoot Tips ◽  
Purine Nucleotides ◽  
Purine Salvage ◽  
Nucleotide Synthesis ◽  
Caffeine Biosynthesis ◽  
Tea Shoot ◽  
Tea Plants ◽  
Almost All

1. The metabolism of xanthine and hypoxanthine in excised shoot tips of tea was studied with micromolar amounts of [2(-14)C]xanthine or [8(-14)C]hypoxanthine. Almost all of the radioactive compounds supplied were utilized by tea shoot tips by 30 h after their uptake. 2. The main products of [2(-14)C]xanthine and [8(-14)C]hypoxanthine metabolism in tea shoots were urea, allantoin and allantoic acid. There was also incorporation of the label into theobromine, caffeine and RNA purine nucleotides. 3. The results indicate that tea plants can catabolize purine bases by the same pathways as animals. It is also suggested that tea plants have the ability to snythesize purine nucleotides from glycine by the pathways of purine biosynthesis de novo and from hypoxanthine and xanthine by the pathway of purine salvage. 4. The results of incorporation of more radioactivity from [8(-14)C]hypoxanthine than from [2(-14)C]xanthine into RNA purine nucleotides and caffeine suggest that hypoxanthine is a more effective precursor of caffeine biosynthesis than xanthine. The formation of caffeine from hypoxanthine is a result of nucleotide synthesis via the pathway of purine salvage.

scholarly journals Metabolism of methionine and biosynthesis of caffeine in the tea plant (Camellia sinensis L.)

1976 ◽  
Vol 160 (2) ◽  
pp. 171-179 ◽  
Author(s):  
T Suzuki ◽  
E Takahashi
Keyword(s):  
Nucleic Acids ◽  
Gradient Centrifugation ◽  
Tea Plant ◽  
Shoot Tips ◽  
Purine Nucleotides ◽  
Unknown Compound ◽  
Caffeine Biosynthesis ◽  
Tea Shoot ◽  
Tea Plants ◽  
Almost All

1. Caffeine biosynthesis was studied by following the incorporation of 14C into the products of L-[Me-14C]methionine metabolism in tea shoot tips. 2. After administration of a ‘pulse’ of L-[Me-14C]methionine, almost all of the L-[Me-14C]methionine supplied disappeared within 1 h, and 14C-labelled caffeine synthesis increased throughout the experimental periods, whereas the radioactivities of an unknown compound and theobromine were highest at 3 h after the uptake of L-[Me-14C]methionine, followed by a steady decrease. There was also slight incorporation of the label into 7-methylxanthine, serine, glutamate and aspartate, disappearing by 36 h after the absorption of L-[Me-14C]methionine. 3. The radioactivities of nucleic acids derived from L-[Me-14C]methionine increased rapidly during the first 12 h incubation period and then decreased steadily. Sedimentation analysis of nucleic acids by sucrose-gradient centrifugation showed that methylation of nucleic acids in tea shoot tips occurred mainly in the tRNA fraction. The main product among the methylated bases in tea shoot tips was identified as 1-methyladenine. 4. The results indicated that the purine ring in caffeine is derived from the purine nucleotides in the nucleotide pool rather than in nucleic acids. A metabolic scheme to show the production of caffeine and related methylxanthines from the nucleotides in tea plants is discussed.

scholarly journals Purine salvage networks in Giardia lamblia.

1983 ◽  
Vol 158 (5) ◽  
pp. 1703-1712 ◽  
Author(s):  
C C Wang ◽  
S Aldritt
Keyword(s):  
Giardia Lamblia ◽  
De Novo ◽  
Adenine Nucleotides ◽  
Guanine Nucleotides ◽  
Rational Approach ◽  
Purine Nucleotides ◽  
Purine Salvage ◽  
Nucleotide Synthesis ◽  
Guanine Base

Purine metabolism in Giardia lamblia was investigated by monitoring incorporation of radiolabeled precursors into purine nucleotides in the log-phase trophozoites cultivated in vitro in axenic media and incubated in buffered saline glucose. The lack of incorporation of formate, glycine, hypoxanthine, inosine, and xanthine into the nucleotide pool suggests the absence of de novo purine nucleotide synthesis and the inability to form IMP as the precursor of AMP and GMP in G. lamblia. Only adenine, adenosine, guanine, and guanosine were incorporated. Further analysis of the labeled nucleotides by HPLC indicated that adenine and adenosine are converted only to adenine nucleotides whereas guanine and guanosine are only incorporated into guanine nucleotides. There is no competition of incorporation between adenine/adenosine and guanine/guanosine, and there is no interconversion between adenine and guanine nucleotides. Results from analyzing [5'-3H]guanosine incorporation indicate that the ribose moiety is not incorporated with the guanine base. Assays of purine salvage enzymic activities in the crude extracts of G. lamblia revealed the presence of only four major enzymes; adenosine and guanosine hydrolases and adenine and guanine phosphoribosyl transferases. Apparently, G. lamblia has an exceedingly simple purine salvage system; it converts adenosine and guanosine to corresponding purine bases and then forms AMP and GMP by the actions of corresponding purine phosphoribosyl transferases. The guanine phosphoribosyl transferase in G. lamblia is interesting because it does not recognize either hypoxanthine or xanthine as substrate. It thus must have a unique substrate specificity and may be regarded as a potential target to attack as a rational approach to chemotherapeutic control of giardiasis.

scholarly journals Metabolism of methylamine in the tea plant (Thea sinensis L.)

1973 ◽  
Vol 132 (4) ◽  
pp. 753-763 ◽  
Author(s):  
Takeo Suzuki
Keyword(s):  
Experimental Period ◽  
Tea Plant ◽  
Shoot Tips ◽  
Purine Nucleotides ◽  
Period 2 ◽  
Tea Plants

1. The metabolism of methylamine in excised shoot tips of tea was studied with micromolar amounts of [14C]methylamine. Of the [14C]methylamine supplied 57% was utilized by tea shoots during the 10h experimental period. 2. The main products of [14C]methylamine metabolism in tea shoots were serine, γ-glutamylmethylamide, theobromine, caffeine and CO2. There was also incorporation of the label into glutamate, aspartate, RNA purine nucleotides and S-adenosylmethionine. 3. The formation of methylamine from γ-glutamylmethylamide was confirmed by feeding tea shoots with γ-glutamyl[14C]methylamide. The products of γ-glutamyl[14C]methylamide metabolism in tea plants were serine, theobromine, caffeine, glutamate and aspartate. 4. The results indicate that the oxidation of methylamine to formaldehyde is the first step of methylamine utilization. Labelled formaldehyde released by the metabolism of methylamine leads to the incorporation of the label into metabolites on the C1 pathways of this compound. It is also suggested that formaldehyde is further oxidized via formate to CO2. 5. The role of γ-glutamylmethylamide in methylamine metabolism in tea plants is discussed. 6. Results support the view that theobromine is the immediate precursor of caffeine.

scholarly journals Crystallographic approach to fragment-based hit discovery against Schistosoma mansoni purine nucleoside phosphorylase

2021 ◽  
Author(s):  
Muhammad Faheem ◽  
Napoleão Fonseca Valadares ◽  
José Brandão-Neto ◽  
Domenico Bellini ◽  
Patrick Collins ◽  
...  
Keyword(s):  
De Novo ◽  
Screening Strategy ◽  
New Drugs ◽  
High Price ◽  
Salvage Pathway ◽  
Purine Salvage ◽  
Nucleotide Synthesis ◽  
Fragment Screening ◽  
Lack Of Information ◽  
Purine Pathway

Several Schistosoma species cause Schistosomiasis, an endemic disease in 78 countries that is ranked second amongst the parasitic diseases in terms of its socioeconomic impact and human health importance. The drug recommended for treatment by the WHO is praziquantel (PZQ), but there are concerns associated with PZQ, such as the lack of information about its exact mechanism of action, its high price, its effectiveness – which is limited to the parasite’s adult form – and reports of resistance. The parasites lack the de novo purine pathway, rendering them dependent on the purine salvage pathway or host purine bases for nucleotide synthesis. Thus, the Schistosoma purine salvage pathway is an attractive target for the development of necessary and selective new drugs. In this study, the purine nucleotide phosphorylase II (PNP2), a new isoform of PNP1, was submitted to a high-throughput fragment-based hit discovery using a crystallographic screening strategy. PNP2 was crystallized and crystals were soaked with 827 fragments, a subset of the Maybridge 1000 library. X-ray diffraction data was collected and structures were solved. Out of 827-screened fragments we have obtained a total of 19 fragments that show binding to PNP2. 14 of these fragments bind to the active site of PNP2, while five were observed in three other sites. Here we present the first fragment screening against PNP2.

scholarly journals INFLUENCE OF X-RAY AND MICROWAVE RADIATION ON DEAMINATION OF PURINE NUCLEOTIDES IN YEAST CELLS CANDIDA GUILLIERMONDII NP-4

2019 ◽  
Vol 62 (2) ◽  
pp. 48-52
Author(s):  
Seda V. Marutyan ◽  
Gayane H. Petrosyan ◽  
Syuzan A. Marutyan ◽  
Liparit A. Navasardyan ◽  
Armen H. Trchounian
Keyword(s):  
Electromagnetic Waves ◽  
De Novo ◽  
Candida Guilliermondii ◽  
Nucleotide Metabolism ◽  
Yeast Cells ◽  
X Rays ◽  
Purine Nucleotides ◽  
Nucleotide Synthesis ◽  
X Ray ◽  
Salvage Pathways

In metabolism of living cells a key role play purine nucleotides which cells can be supplied either by de novo synthesis from lower molecular weight precursors, or by alternate ways of nucleotide synthesis or so-called "nucleotide salvage pathways", which allow reusing of intermediate products of nucleotide metabolism in nucleotide synthesis. This way is important in the post-stress repair period, saving energy and substrates in the repairing cells. Purine nucleotides are allosteric inhibitors of enzymes of nucleotide salvage pathways, therefore the increase in their catabolism leads to a decrease of their amount in the cells, which contributes to the intensive work of the nucleotide salvage pathways and provides substrates for DNA synthesis. Investigation of deamination of purine nucleotides in yeasts Candida guilliermondii NP-4 irradiated with X-rays, millimeter and decimeter electromagnetic waves, as well as after post-radiation incubation of cells has been realized. It has been shown that under the influence of X-ray and microwave irradiation in yeasts, the intensity of deamination of purine nucleotide-polyphosphates - ADP, ATP, GDF and GTP, has changed, which in all probability is an adaptive mechanism in the repair of yeasts after irradiation, provides the work of nucleotide salvage pathways, and can be associated with the metabolism of these compounds.

scholarly journals Identification of sugarcane genes involved in the purine synthesis pathway

2001 ◽  
Vol 24 (1-4) ◽  
pp. 251-255 ◽  
Author(s):  
Mario A. Jancso ◽  
Susana A. Sculaccio ◽  
Otavio H. Thiemann
Keyword(s):  
Expressed Sequence Tag ◽  
De Novo ◽  
Statistical Significance ◽  
Local Alignment ◽  
Central Importance ◽  
Purine Nucleotides ◽  
Nucleotide Synthesis ◽  
Purine Synthesis ◽  
Search Tool ◽  
Expressed Sequence

Nucleotide synthesis is of central importance to all cells. In most organisms, the purine nucleotides are synthesized de novo from non-nucleotide precursors such as amino acids, ammonia and carbon dioxide. An understanding of the enzymes involved in sugarcane purine synthesis opens the possibility of using these enzymes as targets for chemicals which may be effective in combating phytopathogen. Such an approach has already been applied to several parasites and types of cancer. The strategy described in this paper was applied to identify sugarcane clusters for each step of the de novo purine synthesis pathway. Representative sequences of this pathway were chosen from the National Center for Biotechnology Information (NCBI) database and used to search the translated sugarcane expressed sequence tag (SUCEST) database using the available basic local alignment search tool (BLAST) facility. Retrieved clusters were further tested for the statistical significance of the alignment by an implementation (PRSS3) of the Monte Carlo shuffling algorithm calibrated using known protein sequences of divergent taxa along the phylogenetic tree. The sequences were compared to each other and to the sugarcane clusters selected using BLAST analysis, with the resulting table of p-values indicating the degree of divergence of each enzyme within different taxa and in relation to the sugarcane clusters. The results obtained by this strategy allowed us to identify the sugarcane proteins participating in the purine synthesis pathway.

scholarly journals Virtual Screening of Combinatorial Libraries across a Gene Family: in Search of Inhibitors of Giardia lamblia Guanine Phosphoribosyltransferase

2001 ◽  
Vol 45 (9) ◽  
pp. 2571-2576 ◽  
Author(s):  
Alex M. Aronov ◽  
Narsimha R. Munagala ◽  
Irwin D. Kuntz ◽  
Ching C. Wang
Keyword(s):  
Gene Family ◽  
Giardia Lamblia ◽  
De Novo ◽  
Solid Phase ◽  
Three Dimensional ◽  
Combinatorial Libraries ◽  
Protozoan Parasite ◽  
Binding Pocket ◽  
Purine Nucleotides ◽  
Purine Salvage

ABSTRACT Parasitic protozoa lack the ability to synthesize purine nucleotides de novo, relying instead on purine salvage enzymes for their survival. Guanine phosphoribosyltransferase (GPRT) from the protozoan parasite Giardia lamblia is a potential target for rational antiparasitic drug design, based on the experimental evidence, which indicates the lack of interconversion between adenine and guanine nucleotide pools. The present study is a continuation of our efforts to use three-dimensional structures of parasitic phosphoribosyltransferases (PRTs) to design novel antiparasitic agents. Two micromolar phthalimide-based GPRT inhibitors were identified by screening the in-house phthalimide library. A combination of structure-based scaffold selection using virtual library screening across the PRT gene family and solid phase library synthesis led to identification of smaller (molecular weight, <300) ligands with moderate to low specificity for GPRT; the best inhibitors, GP3 and GP5, had K i values in the 23 to 25 μM range. These results represent significant progress toward the goal of designing potent inhibitors of purine salvage inGiardia parasites. As a second step in this process, altering the phthalimide moiety to optimize interactions in the guanine-binding pocket of GPRT is expected to lead to compounds with promising activity against G. lamblia PRT.

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 Optimized sequencing depth and de novo assembler for deeply reconstructing the transcriptome of the tea plant, an economically important plant species

2019 ◽  
Vol 20 (1) ◽  
Author(s):  
Fang-Dong Li ◽  
Wei Tong ◽  
En-Hua Xia ◽  
Chao-Ling Wei
Keyword(s):  
Cultural Values ◽  
Plant Species ◽  
De Novo ◽  
Transcriptome Assembly ◽  
Tea Plant ◽  
Sequencing Depth ◽  
Alcoholic Beverages ◽  
Sequencing Data ◽  
Tea Plants

Abstract Background Tea is the oldest and among the world’s most popular non-alcoholic beverages, which has important economic, health and cultural values. Tea is commonly produced from the leaves of tea plants (Camellia sinensis), which belong to the genus Camellia of family Theaceae. In the last decade, many studies have generated the transcriptomes of tea plants at different developmental stages or under abiotic and/or biotic stresses to investigate the genetic basis of secondary metabolites that determine tea quality. However, these results exhibited large differences, particularly in the total number of reconstructed transcripts and the quality of the assembled transcriptomes. These differences largely result from limited knowledge regarding the optimized sequencing depth and assembler for transcriptome assembly of structurally complex plant species genomes. Results We employed different amounts of RNA-sequencing data, ranging from 4 to 84 Gb, to assemble the tea plant transcriptome using five well-known and representative transcript assemblers. Although the total number of assembled transcripts increased with increasing sequencing data, the proportion of unassembled transcripts became saturated as revealed by plant BUSCO datasets. Among the five representative assemblers, the Bridger package shows the best performance in both assembly completeness and accuracy as evaluated by the BUSCO datasets and genome alignment. In addition, we showed that Bridger and BinPacker harbored the shortest runtimes followed by SOAPdenovo and Trans-ABySS. Conclusions The present study compares the performance of five representative transcript assemblers and investigates the key factors that affect the assembly quality of the transcriptome of the tea plants. This study will be of significance in helping the tea research community obtain better sequencing and assembly of tea plant transcriptomes under conditions of interest and may thus help to answer major biological questions currently facing the tea industry.

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