- Bacterial flavoprotein monooxygenase YxeK salvages toxic S-(2-succino)-adducts via oxygenolytic C–S bond cleavage
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Thiol-containing nucleophiles such as cysteine react spontaneously with the citric acid cycle intermediate fumarate to form S-(2-succino)-adducts. In Bacillus subtilis, a salvaging pathway encoded by the yxe operon has recently been identified for the detoxification and exploitation of these compounds as sulfur sources. This route involves acetylation of S-(2-succino)cysteine to N-acetyl-2-succinocysteine, which is presumably converted to oxaloacetate and N-acetylcysteine, before a final deacetylation step affords cysteine. The critical oxidative cleavage of the C–S bond of N-acetyl-S-(2-succino)cysteine was proposed to depend on the predicted flavoprotein monooxygenase YxeK. Here, we characterize YxeK and verify its role in S-(2-succino)-adduct detoxification and sulfur metabolism. Detailed biochemical and mechanistic investigation of YxeK including 18O-isotope-labeling experiments, homology modeling, substrate specificity tests, site-directed mutagenesis, and (pre-)steady-state kinetics provides insight into the enzyme’s mechanism of action, which may involve a noncanonical flavin-N5-peroxide species for C–S bond oxygenolysis.
- Ellis, Holly R.,Kammerer, Bernd,Lagies, Simon,Matthews, Arne,Sch?nfelder, Julia,Schleicher, Erik,Stull, Frederick,Teufel, Robin
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- Deazaflavins as photocatalysts for the direct reductive regeneration of flavoenzymes
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Deazaflavins are potentially useful redox mediators for the direct, nicotinamide-independent regeneration of oxidoreductases. Especially the O2-stability of their reduced forms have attracted significant interest for the regeneration of monooxygenases. In this contribution we further investigate the photochemical properties of deazaflavins and investigate the scope and limitations of deazaflavin-based photoenzymatic reaction systems.
- van Schie,Younes,Rauch,Pesic,Paul,Arends,Hollmann
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p. 277 - 283
(2018/05/04)
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- Conversion of a Dehalogenase into a Nitroreductase by Swapping its Flavin Cofactor with a 5-Deazaflavin Analogue
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Natural and engineered nitroreductases have rarely supported full reduction of nitroaromatics to their amine products, and more typically, transformations are limited to formation of the hydroxylamine intermediates. Efficient use of these enzymes also requires a regenerating system for NAD(P)H to avoid the costs associated with this natural reductant. Iodotyrosine deiodinase is a member of the same structural superfamily as many nitroreductases but does not directly consume reducing equivalents from NAD(P)H, nor demonstrate nitroreductase activity. However, exchange of its flavin cofactor with a 5-deazaflavin analogue dramatically suppresses its native deiodinase activity and leads to significant nitroreductase activity that supports full reduction to an amine product in the presence of the convenient and inexpensive NaBH4.
- Su, Qi,Boucher, Petrina A.,Rokita, Steven E.
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supporting information
p. 10862 - 10866
(2017/08/30)
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- Dibenzothiophene Catabolism Proceeds via a Flavin-N5-oxide Intermediate
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The dibenzothiophene catabolic pathway converts dibenzothiophene to 2-hydroxybiphenyl and sulfite. The third step of the pathway, involving the conversion of dibenzothiophene sulfone to 2-(2-hydroxyphenyl)-benzenesulfinic acid, is catalyzed by a unique flavoenzyme DszA. Mechanistic studies on this reaction suggest that the C2 hydroperoxide of dibenzothiophene sulfone reacts with flavin to form a flavin-N5-oxide. The intermediacy of the flavin-N5-oxide was confirmed by LC-MS analysis, a co-elution experiment with chemically synthesized FMN-N5-oxide and 18O2 labeling studies.
- Adak, Sanjoy,Begley, Tadhg P.
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supporting information
p. 6424 - 6426
(2016/06/09)
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- Synthesis and electrochemical properties of structurally modified flavin compounds
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Four structurally modified flavin compounds have been synthesized and characterized for their redox potential by chemical reduction with sodium dithionite. Besides the previously reported 1- and 5-deazariboflavin, a 7,8-didemethyl derivative and an 8-isopropylriboflavin have been obtained. The synthesis of these compounds started in all cases from appropriately substituted anilines that were condensed with the ribityl chain, followed by completion of the annealed three-ring structure. The didemethyl- and the isopropyl compounds gave absorption maxima similar to riboflavin (436 and 448 nm, respectively), whereas 1-deazariboflavin showed a bathochromically shifted absorption (λmax = 537 nm), and that of 5-deazariboflavin was hypsochromically shifted (λmax = 400 nm). The midpoint potentials (E0′) of the four modified flavin compounds were determined by potentiometric titration, using riboflavin as a reference compound. Both alkyl-modified flavins showed slightly less negative midpoint potentials, whereas both deaza compounds had more negative midpoint values compared to the reference compound. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Mansurova, Madina,Koay, Melissa S.,Gaertner, Wolfgang
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supporting information; experimental part
p. 5401 - 5406
(2009/05/07)
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- Improved Chemical Syntheses of 1- and 5-Deazariboflavin
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The cofactor flavin adenine dinucleotide (FAD) is required for the catalytic activity of a large class of enzymes known as flavoenzymes. Because flavin cofactors participate in catalysis via a number of different mechanisms, isoalloxazine analogues are valuable for mechanistic studies. We report improved chemical syntheses for the preparation of the two key analogues, 5-deazariboflavin and 1-deazariboflavin.
- Carlson, Erin E.,Kiessling, Laura L.
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p. 2614 - 2617
(2007/10/03)
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- The asymmetric epoxidation of divinyl carbinols: Theory and applications
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The asymmetric epoxidation of symmetric divinyl carbinols is illustrative of a reaction process that combines an initial asymmetric synthesis with a subsequent kinetic resolution to provide products with extraordinary levels of enantiomeric purity. The application of this process to the asymmetric synthesis of natural products is presented herein.
- Smith, David B.,Wang, Zhaoyin,Schreiber, Stuart L.
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p. 4793 - 4808
(2007/10/02)
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- Synthesis of 5-deazaflavin adenine dinucleotide (5-dFAD) using a modified triester approach
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Starting from D-ribose and 3,4-xylidine, a fifteen-step synthesis is described for the preparation of 5-dFAD (18).The synthesis involves as key intermediates, 5-deazariboflavin (8), its 2',3',4'-tris-O-(tetrahydropyranyl) derivative (12) and 2',3',4'-tris-O-(tetrahydropyranyl)-5'-O-(morpholinophosphonyl)-5-deazaribolavin (15).
- Smit, P.,Stork, G. A.,van der Plas, H. C.,den Hartog, J. A. J.,van der Marel, G. A.,van Boom, J. H.
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p. 538 - 543
(2007/10/02)
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- Method of producing solution containing D-ribose
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A D-ribose-containing solution is produced in a high epimerization ratio, such as 60-94%, by epimerizing D-arabinose dissolved in an adequate solvent in the presence of a molybdic acid ion and a boric acid compound. The solution is useful as an inexpensive material on the industrial syntheses of vitamin B2 or nucleic acids.
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- Preparation of N-(D)-ribityl-2-phenylazo-4,5-dimethylaniline
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A process for the preparation of N-(D)-ribityl-2-phenylazo-4,5-dimethylaniline (I), wherein 1. in the case of pure or virtually pure (D)-ribose (III) (a) the latter is reacted with 3,4-dimethylnitrobenzene (IVa) or 3,4-dimethylaniline (IVb) and with hydrogen in the presence of a hydrogenation catalyst, (b) the resulting solution is reacted, in a conventional manner, with an acid phenyldiazonium salt solution (VI) and (c) the resulting product is isolated by crystallization, in a conventional manner, or 2. in the case of crude ribose, ie. industrial mixtures of (D)-ribose and other sugars (a) the crude ribose is reacted with about equimolar amounts, based on III, of 3,4-dimethylaniline (IVb) and boric acid, (b) the boric acid ester of the Schiff base obtained from III and IVb is allowed to crystallize out and is separated off, (c) this ester is hydrogenated with hydrogen in the presence of a hydrogenation catalyst, (d) the solution is freed from catalyst and reacted, in a conventional manner, with an acid phenyldiazonium salt solution and (e) the resulting product I is isolated by crystallization in a conventional manner.
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- Preparation of 5-deazariboflavins
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This invention relates generally to a novel process for preparing 5-deazariboflavins by the cyclization of the corresponding 6-(N-substituted arylamino)uracils with trialkylorthoformate in the presence of a strong acid catalyst. An improved process for preparing the uracil intermediate is also disclosed. More particularly, it is concerned with the process for preparing 5-deazariboflavin by cyclizing 6-[3,4-dimethyl-N-(D-ribityl)anilino[uracil with trialkylorthoformate in the presence of a strong acid catalyst and hydrolyzing the resulting alkoxymethylene derivative. The corresponding uracil intermediate is prepared by reacting 6-chlorouracil with N-D-ribityl-3,4-xylidine. 5-Deazariboflavins having the general Formula (I) herein below: STR1 wherein R7 is hydrogen or methyl, R8 is methyl, hydroxy or acyloxy and R10 is a ribityl group and the corresponding acyl and alkoxymethylene derivatives are useful as riboflavin antagonists with particular utility for the chemotherapy of coccidiosis in chickens or as intermediates for the preparation of said antagonists. The bis(alkoxymethylene) derivatives described herein are useful as prodrug forms of 5-deazariboflavins. When used for the treatment of coccidiosis, such compounds are administered to the animals by way of the feed and are effective in preventing coccidiosis when administered at levels of from about 0.0005% to about 0.05% by weight of the total feed consumed, the amount required for optimum prevention or control of the disease varying with the particular compound employed.
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- 3,4-Xylidine-N-ribityl
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N-[2,3-(O-Isopropylidene)-(D)-ribityl]-3,4-xylidine is a new compound, which can be used as an intermediate for the preparation of N-(D)-ribityl-3,4-xylidine.
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