Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Certaines enzymes impliquées dans le métabolisme intermédiaire sont moins spécifiques pour leur substrat que ce que l'on pense généralement. Ainsi, certaines d'entre-elles commettent des erreurs et forment de manière inappropriée des métabolites non-physiologiques, qui peuvent devenir délétères s'ils ne sont pas détru its. L'UDP-glucose pyrophosphorylase , une enzyme dont la fonction est d'activer le glucose en UDP-glucose, nécessaire pour la synthèse de glycogène, est décrite comme étant peu spécifique pour ses substrats.Le premier objectif de mon mémoire a été de tester la spécificité de l 'UDP-glucose pyrophosphorylase envers le mannose-1-phosphate. En effet, si cette enzyme forme de l'UDP­ mannose, ce métabolite non physiologique pourrait éventuellement être incorporé dans le glycogène et devenir une source de toxicité . Pour tester cette hypothèse, nous avons produit et purifié l'UDP-glucose pyrophosphorylase de souris. L'étude de sa spécificité a montré que l'enzyme recombinante de souris (ainsi que l'enzyme de S. cerevisae) ne forme pas d'UDP­ mannose, mais bien du CDP-glucose et du dTDP-glucose. Le second objectif de mon travail a consisté en la recherche d'une activité pyrophosphatase dans Je foie de rat, capable de réparer l 'erreur produite par l'UDP-glucose pyrophosphorylase, à l'aide d'un dosage radiochimique que nous avons mis au point. Nous avons pu identifier au moins deux types d'activités pyrophosphatase capables d'hydrolyser le CDP-glucose ainsi que le dTDP­ glucose. Une caractérisation plus approfondie de ces activités enzymatiques a montré qu'aucune des deux n'apparaît comme très intéressante, puisqu 'elles agissent également sur l'UDP-glucose, le produit spécifique de la réaction catalysée par l'UDP-glucose pyrophosphorylase. De plus, une d'entre elles est inhibée par plusieurs nucléotides et dépendante de la présence de Zn2 . Ses propriétés nous font penser qu'elle correspond vraisemblablement à une contamination de l'extrait par des ecto-enzymes membranaires qui ont leur site catalytique extracellulaire et non à une « enzyme de réparation » qui rendrait la synthèse de glycogène plus spécifique. L'autre activité enzymatique, qui semblait plus spécifique pour l'UDP-glucose, semble être contribuée par la galactose-1-phosphate uridylyltransferase, une enzyme clé du métabolisme du galactose très active dans le foie.Le troisième objectif de mon mémoire a été d'en savoir plus sur le rôle de NUDT14 , une UDP-glucose pyrophosphatase d'après la littérature, ainsi que sur celui de NU DT5, l 'enzyme mammalienne la plus proche de NUDT14. Nous avons montré que l'UDP-glucose n'est substrat de NUDT1 4 qu'à des pH alcalins, et qu'à pH physiologique, différents dérivés de I'ADP (normaux ou altérés) sont de bien meilleurs substrats que l'UDP-glucose. Ceci suggère que le substrat physiologique de NUDT14 est un nucléotide, peut-être non-classique ou abîmé, contenant de l'adénine, qui est métabolisé ou recyclé. Quant à NUDT5 , les deux meilleurs substrats que nous avons trouvés sont I'ADP-ribose et l'ADP-glucose. Puisque I'ADP-glucose n'est pas physiologique chez les mammifères et que nos cellules ont déjà une ADP-ribose pyrophosphatase (NUDT9) qui est très spécifique, il est aussi probable que NUDT5 ait une fonction qui soit autre que d'hydrolyser de I'ADP-ribose. En plus, nous avons utilisé le système CRISPR/CAS9 pour produire des lignées de cellules HCTI 16 déficientes en NUDT14 ou en NUDT5 qui pourront être utiles pour en savoir plus sur le rôle physiologique de ces deux protéines. It is becoming widely recognized that some enzymes involved in the intermediary metabolism are less specific than previously thought for their substrates. Indeed, some of them make mistakes and form non­ physiological metabolites that can accumulate and become toxic. The UDP-glucose pyrophosphorylase , the enzyme that converts glucose }-phosphate to UDP-glucose, required for the glycogen synthesis, is described in literature as lacking substrate specificity.The first objective of my research was to test the specificity of this enzyme for mannose 1-phosphate. Indeed, if UDP-glucose pyrophosphorylase could make UDP-mannose under physiological conditions, this non-physiological substrate might accumulate, be incorporated in glycogen and possibly become toxic for the cells. To validate this hypothesis, we produced and purified recombinant mouse UDP­ glucose pyrophosphorylase. The study of the substrate specificity for this enzyme showed that neither the mouse nor the S. cerevisae enzymes make UDP-mannose, but that they both produce small amounts of CDP-glucose and dTDP-glucose.This stimulated us to look in a rat liver extract, for a pyrophosphatase with an enzymatic activity that would be able to fix the metabolic mistake of UDP-glucose pyrophosphorylase. Using a radiochemical assay that we have developed, we identified at least two different pyrophosphatase activities hydrolyzing CDP-glucose and dTDP-glucose. However, their detailed characterization has shown that neither of them appeared to be very interesting, because they can also act on the UDP-glucose, the main product of the reaction catalysed by UDP-glucose pyrophosphorylase. Moreover, one of the enzymatic activities was inhibited by various nucleotides and was dependent on the presence of Zn2 . Its properties suggest that it probably corresponds to a contamination of the extract with ecto-enzymes that got detached from the membrane and which have an extracellular catalytic site. Therefore this activity does not correspond to a "repair enzyme" that would make the synthesis of the glycogen more specific. The other enzymatic activity, which seemed more specific for the UDP-glucose, appears to be contributed by galactose !­ phosphate uridyltransferase , an enzyme of galactose metabolism that is very active in the liver.In the third part of my work we addressed the function of NUDT14 , a pyrophosphatase from the NUDIX family of proteins that was previously described as an UDP-glucose pyrophosphorylase, as well as the role of NUDT5 that is its closest mammalian homologue. We could show that UDP-glucose is only a substrate of NUDT14 at alkaline pH and that at physiological pH various ADP-derivatives (normal or altered) are better substrates than the UDP-glucose. This suggests that the physiological substrate of NUDT14 is a nucleotide, but maybe a non-classical one or a damaged one, containing an adenine, which would need to be metabolized or recycled. Regarding NUDT5, the two bests substrates that we found are ADP-ribose and ADP-glucose, that have already been described. However, since ADP-glucose is not physiological in mammalian cells, and that they already appear to have a very specific ADP-ribose pyrophosphatase (NUDT9) it is possible that NUDT5 has another function different from the hydrolysis the ADP-ribose. In this context, we have used the CR1SPR/CAS9 system to produce HCTl 16 cell lines that are deficient in NUDTI 4 or in NUDT5, which might be useful to learn more about the physiological role of these proteins.

UTP-Glucose-1-Phosphate Uridylyltransferase --- Nudt14 protein, mouse --- Uridine Diphosphate Sugars

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

RNA Modification provides a useful examination of the science and its role in biological regulation, the current frontier of life science research, and includes various RNA modications and their role in gene expression. It represents the most up-to-date knowledge and protocols available today.

• Dynamic RNA modifications and their roles in biological regulation are the current frontier of life science research
• This volume of Methods in Enzymology represents up to date knowledge and protocols

RNA Processing, Post-Transcriptional --- Pseudouridine --- RNA, Transfer --- Gene Expression Regulation --- Uridine --- Biochemical Processes --- RNA --- Metabolism --- Genetic Processes --- Ribonucleosides --- Pyrimidine Nucleosides --- Biochemical Phenomena --- Chemical Processes --- Nucleic Acids --- Metabolic Phenomena --- Nucleosides --- Genetic Phenomena --- Nucleic Acids, Nucleotides, and Nucleosides --- Phenomena and Processes --- Chemical Phenomena --- Pyrimidines --- Chemicals and Drugs --- Heterocyclic Compounds, 1-Ring --- Heterocyclic Compounds --- Animal Biochemistry --- Human Anatomy & Physiology --- Health & Biological Sciences --- RNA editing. --- ARN --- pharmacokinetics --- Edition --- Editing, RNA --- Messenger RNA editing --- mRNA editing --- RNA Processing, Post-Transcriptional. --- pharmacokinetics. --- Genetic regulation

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Bacterial toxin–antitoxin (TA) systems, which are ubiquitously present in bacterial genomes, are not essential for normal cell proliferation. The TA systems regulate fundamental cellular processes, facilitate survival under stress conditions, have essential roles in virulence and represent potential therapeutic targets. These genetic TA loci are also shown to be involved in the maintenance of successful multidrug-resistant mobile genetic elements. The TA systems are classified as types I to VI, according to the nature of the antitoxin and to the mode of toxin inhibition. Type II TA systems encode a labile antitoxin and its stable toxin; degradation of the antitoxin renders a free toxin, which is bacteriostatic by nature. A free toxin generates a reversible state with low metabolic activity (quiescence) by affecting important functions of bacterial cells such as transcription, translation, DNA replication, replication and cell-wall synthesis, biofilm formation, phage predation, the regulation of nucleotide pool, etc., whereas antitoxins are toxin inhibitors. Under stress conditions, the TA systems might form networks. To understand the basis of the unique response of TA systems to stress, the prime causes of the emergence of drug-resistant strains, and their contribution to therapy failure and the development of chronic and recurrent infections, must be known in order to grasp how TA systems contribute to the mechanisms of phenotypic heterogeneity and pathogenesis that will enable the rational development of new treatments for infections caused by pathogens.

Medicine --- tuberculosis --- toxin-antitoxin systems --- bacterial cell death --- NAD+ --- stress-response --- toxin-antitoxin system --- mazF --- type II --- toxin --- mRNA interferase --- X-ray crystallography --- cognate interactions --- cross-interactions --- molecular insulation --- antitoxin --- TA systems --- addiction --- anti-addiction --- type I toxin-antitoxin system --- small protein toxin structure --- Fst/Ldr family --- toxin-antitoxin --- M. tuberculosis --- bacteria --- pathogenesis --- protein-protein interactions --- cross-talk --- protein interface --- tolerance --- persistence --- cross-resistance --- toxin-antitoxin system --- PemI/PemK --- Klebsiella pneumoniae --- toxin-antitoxin systems --- toxin activation --- antibacterial agents --- bacterial persistence --- Stenotrophomonas maltophilia --- opportunistic pathogen --- clinical origin --- environmental origin --- biofilm --- antibiotic resistance --- cell wall inhibition --- nucleotide hydrolysis --- uridine diphosphate-N-acetylglucosamine --- tuberculosis --- toxin-antitoxin systems --- bacterial cell death --- NAD+ --- stress-response --- toxin-antitoxin system --- mazF --- type II --- toxin --- mRNA interferase --- X-ray crystallography --- cognate interactions --- cross-interactions --- molecular insulation --- antitoxin --- TA systems --- addiction --- anti-addiction --- type I toxin-antitoxin system --- small protein toxin structure --- Fst/Ldr family --- toxin-antitoxin --- M. tuberculosis --- bacteria --- pathogenesis --- protein-protein interactions --- cross-talk --- protein interface --- tolerance --- persistence --- cross-resistance --- toxin-antitoxin system --- PemI/PemK --- Klebsiella pneumoniae --- toxin-antitoxin systems --- toxin activation --- antibacterial agents --- bacterial persistence --- Stenotrophomonas maltophilia --- opportunistic pathogen --- clinical origin --- environmental origin --- biofilm --- antibiotic resistance --- cell wall inhibition --- nucleotide hydrolysis --- uridine diphosphate-N-acetylglucosamine

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

The Special Issue “Molecules from Side Reactions” is a collection of papers reporting on the synthesis and characterization of the molecules that come from unexpected synthetic routes. This is the first example of a Special Issue based on such a topic, notwithstanding that all synthetic chemists have isolated a side product during a chemical reaction. Instead of continuing to store the side products in the freezer, I have thought to give them the dignity of publication, making them available to the scientific community. The short manuscripts collected here respect the principle of “one compound per paper” and have the purpose of preserving the molecular diversity deriving from a chemical reaction. The molecular scaffolds are unexpected and intriguing, and could be useful starting points or intermediates for exploring novel reactions.

History of engineering & technology --- oxazole --- furan --- RORC reaction --- (E,Z)-isomerization --- nitration --- azaheterocycles --- N–C bond cleavage --- pyridine-imidazolium --- ribose --- psicose --- ketose --- rare sugar --- hydroxy methylation --- AICAR --- acadesine --- phosphorylation --- fluorination --- fluorinated nucleosides --- nucleoside analogues --- modified nucleosides --- chlorinated nucleosides --- AMPK --- organic synthesis --- bidentate directing groups --- benzamides --- chelation assistance --- bis-chelates --- C–H bond functionalization --- X-ray structure determination --- N′-acetylhydrazide --- 3-acetyl-2,3-dihydro-1,3,4-oxadiazole --- 1H-pyrazolo[3,4-b]pyridine --- heterocycle --- oxetane --- epoxide --- rearrangement --- carbohydrate --- C-glycosylation --- spiro-oxetane --- ester group migration --- glycosyl sulfoxide --- uronate --- thioglycoside oxidation --- mannose --- 8-Fluoro-2′-deoxyguanosine --- 19F NMR spectroscopy --- solid phase synthesis --- phosphoramidite --- muraymycins --- caprazamycins --- nucleosides --- uridine --- cyclization --- seven-membered rings --- conjugated diyne --- LAH reduction --- diacetal --- pent-1,2,3,4-tetraene intermediate --- ligand --- pyridine derivatives --- allenic compounds --- N-alkylation --- copper --- cyanide --- network --- guanidinium --- unexpected iminium cation --- n/a --- N-C bond cleavage --- C-H bond functionalization --- N'-acetylhydrazide --- 8-Fluoro-2'-deoxyguanosine

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

This reprint presents some recent results from applying original analytical methods to the most renowned hive matrices. Particular consideration was given to methods devoted to the attribution of the origin of honey and propolis, but also studies dealing with the chemical characterization of honey and other hive matrices are here reported. Attention has also been paid to the use of optimized methods of elemental analysis in several hive products for quality and safety purposes, but also for environmental biomonitoring. The treatment of the data was often achieved through multivariate analysis methods, which made it possible to obtain reliable classifications of honeys and propolis according to their botanic or geographical origin.

propolis --- poplar --- HPLC–Q-Exactive-Orbitrap®–MS analysis --- phenolic glycerides --- essential and non-essential nutrients --- nucleosides --- honey composition --- uridine --- neuropharmacological activities --- filtered honey --- botanical origin --- fluorescence spectrometry --- antioxidant activity --- spectrum–effect relationships --- cluster analysis --- principal component analysis --- multiple linear regression analysis --- sample preparation --- trace element --- toxic element --- spectroanalytical technique --- biomonitoring --- bee pollen --- ascorbic acid --- total ascorbic acids --- dehydroascorbic acid --- HILIC --- honey discrimination --- strawberry-tree --- thistle --- eucalyptus --- asphodel --- attenuated total reflectance --- Fourier transform infrared spectroscopy --- bee products --- multielemental analysis --- ICP-MS --- ICP-OES --- inorganic contaminants --- heavy metals --- honey --- quality standards --- protein --- amylase --- acid phosphatase --- native PAGE --- royal jelly --- proteins --- ProteoMinerTM --- MALDI-TOF-MS --- proteomics --- beehive product --- unedone --- bitter taste --- strawberry tree honey --- LC-ESI/LTQ-Orbitrap-MS --- PCA --- PLS --- aroma composition --- sugar content --- QDA profile --- HMF --- furanic aldehydes --- furanic acids --- homogentisic acid --- cyclic voltammetry --- square wave voltammetry --- RP-HPLC --- bees --- beehive products --- cold vapor atomic fluorescence spectrometry --- toxic metal --- trace elements --- toxic elements --- geographical origin --- strawberry tree