83-88-5Relevant articles and documents
Studies on the reaction between reduced riboflavin and selenocystine
Dereven'kov, Ilia A.,Makarov, Sergei V.,Molodtsov, Pavel A.,Makarova, Anna S.
, p. 146 - 153 (2020/09/21)
Selenocysteine (Sec) is a crucial component of mammalian thioredoxin reductase (TrxR) where it serves as a nucleophile for disulfide bond rupture in thioredoxin (Trx). Generation of the reduced state of Sec in TrxR requires consecutive two electron transfer steps, namely: (i) from NADPH to flavin adenine dinucleotide, (ii) from reduced flavin to the disulfide bond Cys59-S-S-Cys64, and finally (iii) from Cys59 and Cys64 to the selenosulfide bond Cys497-S-Se-Sec498. In this work, we studied the reaction between reduced riboflavin (RibH2) and selenocystine (Sec-Sec), an oxidized form of Sec. The interaction between RibH2 and Sec-Sec proceeded relatively slowly in comparison with its reverse reaction, that is, reduction of riboflavin (Rib) by Sec. The rate constant for the reaction between RibH2 and Sec-Sec was (7.9?±?0.1)?×?10?2?M?1 s?1 (pH 7.0, 25.0°C). The reaction between Rib and Sec proceeded via two steps, namely, a rapid reversible binding of Rib to Sec having a protonated selenol group to form a Sec-Rib complex, followed by nucleophilic attack of Sec-Rib by a second Sec molecule harboring a deprotonated selenol group. The equilibrium constant for the overall reduction process of Rib by Sec is (1.2?±?0.1)?×?106?M?1 (25.0°C). The finding that the interaction of RibH2 with oxidized selenol is reversible with its equilibrium favored toward the reverse reaction provides an additional explanation for the exceptional mechanism of the mammalian Trx/TrxR system involving transient reduction of a disulfide bond.
A high-throughput screening for inhibitors of riboflavin synthase identifies novel antimicrobial compounds to treat brucellosis
Serer, María Inés,Carrica, Mariela del Carmen,Trappe, J?rg,López Romero, Sandra,Bonomi, Hernán Ruy,Klinke, Sebastián,Cerutti, María Laura,Goldbaum, Fernando Alberto
, p. 2522 - 2535 (2019/04/17)
Brucella spp. are pathogenic intracellular Gram-negative bacteria adapted to life within cells of several mammals, including humans. These bacteria are the causative agent of brucellosis, one of the zoonotic infections with the highest incidence in the world and for which a human vaccine is still unavailable. Current therapeutic treatments against brucellosis are based on the combination of two or more antibiotics for prolonged periods, which may lead to antibiotic resistance in the population. Riboflavin (vitamin B2) is biosynthesized by microorganisms and plants but mammals, including humans, must obtain it from dietary sources. Owing to the absence of the riboflavin biosynthetic enzymes in animals, this pathway is nowadays regarded as a rich resource of targets for the development of new antimicrobial agents. In this work, we describe a high-throughput screening approach to identify inhibitors of the enzymatic activity of riboflavin synthase, the last enzyme in this pathway. We also provide evidence for their subsequent validation as potential drug candidates in an in?vitro brucellosis infection model. From an initial set of 44?000 highly diverse low molecular weight compounds with drug-like properties, we were able to identify ten molecules with 50% inhibitory concentrations in the low micromolar range. Further Brucella culture and intramacrophagic replication experiments showed that the most effective bactericidal compounds share a 2-Phenylamidazo[2,1-b][1,3]benzothiazole chemical scaffold. Altogether, these findings set up the basis for the subsequent lead optimization process and represent a promising advancement in the pursuit of novel and effective antimicrobial compounds against brucellosis.
Site-Selective Synthesis of 15N- and 13C-Enriched Flavin Mononucleotide Coenzyme Isotopologues
Neti, Syam Sundar,Poulter, C. Dale
, p. 5087 - 5092 (2016/07/06)
Flavin mononucleotide (FMN) is a coenzyme for numerous proteins involved in key cellular and physiological processes. Isotopically labeled flavin is a powerful tool for studying the structure and mechanism of flavoenzyme-catalyzed reactions by a variety of techniques, including NMR, IR, Raman, and mass spectrometry. In this report, we describe the preparation of labeled FMN isotopologues enriched with 15N and 13C isotopes at various sites in the pyrazine and pyrimidine rings of the isoalloxazine core of the cofactor from readily available precursors by a five-step chemo-enzymatic synthesis.
Single label comparative hybridization
-
, (2015/01/06)
The present invention provides methods of detecting and mapping chromosomal or genetic abnormalities associated with various diseases or with predisposition to various diseases, or to detecting the phenomena of large scale copy number variants. In particular, the present invention provides advanced methods of performing array-based comparative hybridization that allow reproducibility between samples and enhanced sensitivity by using the same detectable label for both test sample and reference sample nucleic acids. Invention methods are useful for the detection or diagnosis of particular disease conditions such as cancer, and detecting predisposition to cancer based on detection of chromosomal or genetic abnormalities and gene expression level. Invention methods are also useful for the detection or diagnosis of hereditary genetic disorders or predisposition thereto, especially in prenatal samples. Moreover, invention methods are also useful for the detection or diagnosis of de novo genetic aberrations associated with post-natal developmental abnormalities.
A solid-state pH sensor for nonaqueous media including ionic liquids
Thompson, Brianna C.,Winther-Jensen, Orawan,Winther-Jensen, Bjorn,Macfarlane, Douglas R.
, p. 3521 - 3525 (2013/05/22)
We describe a solid state electrode structure based on a biologically derived proton-active redox center, riboflavin (RFN). The redox reaction of RFN is a pH-dependent process that requires no water. The electrode was fabricated using our previously described 'stuffing' method to entrap RFN into vapor phase polymerized poly(3,4-ethylenedioxythiophene). The electrode is shown to be capable of measuring the proton activity in the form of an effective pH over a range of different water contents including nonaqueous systems and ionic liquids (ILs). This demonstrates that the entrapment of the redox center facilitates direct electron communication with the polymer. This work provides a miniaturizable system to determine pH (effective) in nonaqueous systems as well as in ionic liquids. The ability to measure pH (effective) is an important step toward the ability to customize ILs with suitable pH (effective) for catalytic reactions and biotechnology applications such as protein preservation.
Nucleic acid size detection method
-
, (2012/05/04)
The present invention provides methods of determining the size of a particular nucleic acid segment of interest in a sample of nucleic acids through fragmentation of DNA, size fractionation, an optional second fragmentation, and identification using a marker sequence. In particular aspects, an expansion or reduction of tandem repeat sequences can be detected. In further aspects, carriers and individuals afflicted with fragile X syndrome or other diseases associated with tandem repeats can be distinguished from normal individuals.
O-nucleoside, S-nucleoside, and N-nucleoside probes of lumazine synthase and riboflavin synthase
Talukdar, Arindam,Zhao, Yujie,Lv, Wei,Bacher, Adelbert,Illarionov, Boris,Fischer, Markus,Cushman, Mark
experimental part, p. 6239 - 6261 (2012/09/25)
Lumazine synthase catalyzes the penultimate step in the biosynthesis of riboflavin, while riboflavin synthase catalyzes the last step. O-Nucleoside, S-nucleoside, and N-nucleoside analogues of hypothetical lumazine biosynthetic intermediates have been synthesized in order to obtain structure and mechanism probes of these two enzymes, as well as inhibitors of potential value as antibiotics. Methods were devised for the selective cleavage of benzyl protecting groups in the presence of other easily reduced functionality by controlled hydrogenolysis over Lindlar catalyst. The deprotection reaction was performed in the presence of other reactive functionality including nitro groups, alkenes, and halogens. The target compounds were tested as inhibitors of lumazine synthase and riboflavin synthase obtained from a variety of microorganisms. In general, the S-nucleosides and N-nucleosides were more potent than the corresponding O-nucleosides as lumazine synthase and riboflavin synthase inhibitors, while the C-nucleosides were the least potent. A series of molecular dynamics simulations followed by free energy calculations using the Poisson-Boltzmann/surface area (MM-PBSA) method were carried out in order to rationalize the results of ligand binding to lumazine synthase, and the results provide insight into the dynamics of ligand binding as well as the molecular forces stabilizing the intermediates in the enzyme-catalyzed reaction.
Oxygen reactivity in flavoenzymes: Context matters
McDonald, Claudia A.,Fagan, Rebecca L.,Collard, Francois,Monnier, Vincent M.,Palfey, Bruce A.
supporting information; experimental part, p. 16809 - 16811 (2011/12/04)
Many flavoenzymes-oxidases and monooxygenases-react faster with oxygen than free flavins do. There are many ideas on how enzymes cause this. Recent work has focused on the importance of a positive charge near N5 of the reduced flavin. Fructosamine oxidase has a lysine near N5 of its flavin. We measured a rate constant of 1.6 × 105 M-1 s-1 for its reaction with oxygen. The Lys276Met mutant reacted with a rate constant of 291 M-1 s-1, suggesting an important role for this lysine in oxygen activation. The dihydroorotate dehydrogenases from E. coli and L. lactis also have a lysine near N5 of the flavin. They react with O2 with rate constants of 6.2 × 104 and 3.0 × 103 M-1 s-1, respectively. The Lys66Met and Lys43Met mutant enzymes react with rate constants that are nearly the same as those for the wild-type enzymes, demonstrating that simply placing a positive charge near N5 of the flavin does not guarantee increased oxygen reactivity. Our results show that the lysine near N5 does not exert an effect without an appropriate context; evolution did not find only one mechanism for activating the reaction of flavins with O2.
Aerobic reduction of olefins by in situ generation of diimide with synthetic flavin catalysts
Imada, Yasushi,Iida, Hiroki,Kitagawa, Takahiro,Naota, Takeshi
body text, p. 5908 - 5920 (2011/07/07)
A versatile reducing agent, diimide, can be generated efficiently by the aerobic oxidation of hydrazine with neutral and cationic synthetic flavin catalysts 1 and 2. This technique provides a convenient and safe method for the aerobic reduction of olefins, which proceeds with 1 equiv of hydrazine under an atmosphere of O2 or air. The synthetic advantage over the conventional gas-based method has been illustrated through high hydrazine efficiency, easy and safe handling, and characteristic chemoselectivity. Vitamin B2 derivative 6 acts as a highly practical, robust catalyst for this purpose because of its high availability and recyclability. Association complexes of 1b with dendritic 2,5-bis(acylamino)pyridine 15 exhibit unprecedented catalytic activities, with the reduction of aromatic and hydroxy olefins proceeding significantly faster when a higher-generation dendrimer is used as a host pair for the association catalysts. Contrasting retardation is observed upon similar treatment of non-aromatic or non-hydroxy olefins with the dendrimer catalysts. Control experiments and kinetic studies revealed that these catalytic reactions include two independent, anaerobic and aerobic, processes for the generation of diimide from hydrazine. Positive and negative dendrimer effects on the catalytic reactions have been ascribed to the specific inclusion of hydrazine and olefinic substrates into the enzyme-like reaction cavities of the association complex catalysts. Copyright
Virtual screening, selection and development of a benzindolone structural scaffold for inhibition of lumazine synthase
Talukdar, Arindam,Morgunova, Ekaterina,Duan, Jianxin,Meining, Winfried,Foloppe, Nicolas,Nilsson, Lennart,Bacher, Adelbert,Illarionov, Boris,Fischer, Markus,Ladenstein, Rudolf,Cushman, Mark
experimental part, p. 3518 - 3534 (2010/08/05)
Virtual screening of a library of commercially available compounds versus the structure of Mycobacterium tuberculosis lumazine synthase identified 2-(2-oxo-1,2-dihydrobenzo[cd]indole-6-sulfonamido)acetic acid (9) as a possible lead compound. Compound 9 proved to be an effective inhibitor of M. tuberculosis lumazine synthase with a Ki of 70 μM. Lead optimization through replacement of the carboxymethylsulfonamide sidechain with sulfonamides substituted with alkyl phosphates led to a four-carbon phosphate 38 that displayed a moderate increase in enzyme inhibitory activity (Ki 38 μM). Molecular modeling based on known lumazine synthase/inhibitor crystal structures suggests that the main forces stabilizing the present benzindolone/enzyme complexes involve π-π stacking interactions with Trp27 and hydrogen bonding of the phosphates with Arg128, the backbone nitrogens of Gly85 and Gln86, and the side chain hydroxyl of Thr87.
