Journal articles: 'Flavin hydroquinone dependent Enzymes'

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Perry, Lynda L., and Gerben J. Zylstra. "Cloning of a Gene Cluster Involved in the Catabolism of p-Nitrophenol by Arthrobacter sp. Strain JS443 and Characterization of the p-Nitrophenol Monooxygenase." Journal of Bacteriology 189, no. 21 (August 24, 2007): 7563–72. http://dx.doi.org/10.1128/jb.01849-06.

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ABSTRACT The npd gene cluster, which encodes the enzymes of a p-nitrophenol catabolic pathway from Arthrobacter sp. strain JS443, was cloned and sequenced. Three genes, npdB, npdA1, and npdA2, were independently expressed in Escherichia coli in order to confirm the identities of their gene products. NpdA2 is a p-nitrophenol monooxygenase belonging to the two-component flavin-diffusible monooxygenase family of reduced flavin-dependent monooxygenases. NpdA1 is an NADH-dependent flavin reductase, and NpdB is a hydroxyquinol 1,2-dioxygenase. The npd gene cluster also includes a putative maleylacetate reductase gene, npdC. In an in vitro assay containing NpdA2, an E. coli lysate transforms p-nitrophenol stoichiometrically to hydroquinone and hydroxyquinol. It was concluded that the p-nitrophenol catabolic pathway in JS443 most likely begins with a two-step transformation of p-nitrophenol to hydroxy-1,4-benzoquinone, catalyzed by NpdA2. Hydroxy-1,4-benzoquinone is reduced to hydroxyquinol, which is degraded through the hydroxyquinol ortho cleavage pathway. The hydroquinone detected in vitro is a dead-end product most likely resulting from chemical or enzymatic reduction of the hypothetical intermediate 1,4-benzoquinone. NpdA2 hydroxylates a broad range of chloro- and nitro-substituted phenols, resorcinols, and catechols. Only p-nitro- or p-chloro-substituted phenols are hydroxylated twice. Other substrates are hydroxylated once, always at a position para to a hydroxyl group.

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Mihasan, Marius, Calin-Bogdan Chiribau, Thorsten Friedrich, Vlad Artenie, and Roderich Brandsch. "An NAD(P)H-Nicotine Blue Oxidoreductase Is Part of the Nicotine Regulon and May Protect Arthrobacter nicotinovorans from Oxidative Stress during Nicotine Catabolism." Applied and Environmental Microbiology 73, no. 8 (February 9, 2007): 2479–85. http://dx.doi.org/10.1128/aem.02668-06.

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ABSTRACT An NAD(P)H-nicotine blue (quinone) oxidoreductase was discovered as a member of the nicotine catabolic pathway of Arthrobacter nicotinovorans. Transcriptional analysis and electromobility shift assays showed that the enzyme gene was expressed in a nicotine-dependent manner under the control of the transcriptional activator PmfR and thus was part of the nicotine regulon of A. nicotinovorans. The flavin mononucleotide-containing enzyme uses NADH and, with lower efficiency, NADPH to reduce, by a two-electron transfer, nicotine blue to the nicotine blue leuco form (hydroquinone). Besides nicotine blue, several other quinones were reduced by the enzyme. The NAD(P)H-nicotine blue oxidoreductase may prevent intracellular one-electron reductions of nicotine blue which may lead to semiquinone radicals and potentially toxic reactive oxygen species.

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Hyster, Todd K. "Radical Biocatalysis: Using Non-Natural Single Electron Transfer Mechanisms to Access New Enzymatic Functions." Synlett 31, no. 03 (May 7, 2019): 248–54. http://dx.doi.org/10.1055/s-0037-1611818.

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Exploiting non-natural reaction mechanisms within native enzymes is an emerging strategy for expanding the synthetic capabilities of biocatalysts. When coupled with modern protein engineering techniques, this approach holds great promise for biocatalysis to address long-standing selectivity and reactivity challenges in chemical synthesis. Controlling the stereochemical outcome of reactions involving radical intermediates, for instance, could benefit from biocatalytic solutions because these reactions are often difficult to control by using existing small molecule catalysts. General strategies for catalyzing non-natural radical reactions within enzyme active sites are, however, undeveloped. In this account, we highlight three distinct strategies developed in our group that exploit non-natural single electron transfer mechanisms to unveil previously unknown radical biocatalytic functions. These strategies allow common oxidoreductases to be used to address the enduring synthetic challenge of asymmetric hydrogen atom transfer.1 Introduction2 Photoinduced Electron Transfer from NADPH3 Ground State Electron Transfer from Flavin Hydroquinone4 Enzymatic Redox Activation in NADPH-Dependent Oxidoreductases5 Conclusion

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Wojcieszyńska, Danuta, Katarzyna Hupert-Kocurek, and Urszula Guzik. "Flavin-Dependent Enzymes in Cancer Prevention." International Journal of Molecular Sciences 13, no. 12 (December 7, 2012): 16751–68. http://dx.doi.org/10.3390/ijms131216751.

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Hilvert, Donald, and E. T. Kaisert. "Semisynthetic Enzymes: Design of Flavin-Dependent Oxidoreductases." Biotechnology and Genetic Engineering Reviews 5, no. 1 (September 1987): 297–318. http://dx.doi.org/10.1080/02648725.1987.10647841.

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Menon, Binuraj R. K., Jonathan Latham, Mark S. Dunstan, Eileen Brandenburger, Ulrike Klemstein, David Leys, Chinnan Karthikeyan, Michael F. Greaney, Sarah A. Shepherd, and Jason Micklefield. "Structure and biocatalytic scope of thermophilic flavin-dependent halogenase and flavin reductase enzymes." Organic & Biomolecular Chemistry 14, no. 39 (2016): 9354–61. http://dx.doi.org/10.1039/c6ob01861k.

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Mügge, Carolin, Thomas Heine, Alvaro Gomez Baraibar, Willem J. H. van Berkel, Caroline E. Paul, and Dirk Tischler. "Flavin-dependent N-hydroxylating enzymes: distribution and application." Applied Microbiology and Biotechnology 104, no. 15 (June 5, 2020): 6481–99. http://dx.doi.org/10.1007/s00253-020-10705-w.

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Moon, Shin, and Choe. "Crystal Structures of Putative Flavin Dependent Monooxygenase from Alicyclobacillus Acidocaldarius." Crystals 9, no. 11 (October 23, 2019): 548. http://dx.doi.org/10.3390/cryst9110548.

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Flavin dependent monooxygenases catalyze various reactions to play a key role in biological processes, such as catabolism, detoxification, and biosynthesis. Group D flavin dependent monooxygenases are enzymes with an Acyl-CoA dehydrogenase (ACAD) fold and use Flavin adenine dinucleotide (FAD) or Flavin mononucleotide (FMN) as a cofactor. In this research, crystal structures of Alicyclobacillus acidocaldarius protein formerly annotated as an ACAD were determined in Apo and FAD bound state. Although our structure showed high structural similarity to other ACADs, close comparison of substrate binding pocket and phylogenetic analysis showed that this protein is more closely related to other bacterial group D flavin dependent monooxygenases, such as DszC (sulfoxidase) and DnmZ and Kijd3 (nitrososynthases).

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Shepherd, Sarah A., Chinnan Karthikeyan, Jonathan Latham, Anna-Winona Struck, Mark L. Thompson, Binuraj R. K. Menon, Matthew Q. Styles, Colin Levy, David Leys, and Jason Micklefield. "Extending the biocatalytic scope of regiocomplementary flavin-dependent halogenase enzymes." Chemical Science 6, no. 6 (2015): 3454–60. http://dx.doi.org/10.1039/c5sc00913h.

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Saleem-Batcha, Raspudin, Frederick Stull, Jacob N. Sanders, Bradley S. Moore, Bruce A. Palfey, K. N. Houk, and Robin Teufel. "Enzymatic control of dioxygen binding and functionalization of the flavin cofactor." Proceedings of the National Academy of Sciences 115, no. 19 (April 23, 2018): 4909–14. http://dx.doi.org/10.1073/pnas.1801189115.

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The reactions of enzymes and cofactors with gaseous molecules such as dioxygen (O2) are challenging to study and remain among the most contentious subjects in biochemistry. To date, it is largely enigmatic how enzymes control and fine-tune their reactions with O2, as exemplified by the ubiquitous flavin-dependent enzymes that commonly facilitate redox chemistry such as the oxygenation of organic substrates. Here we employ O2-pressurized X-ray crystallography and quantum mechanical calculations to reveal how the precise positioning of O2 within a flavoenzyme’s active site enables the regiospecific formation of a covalent flavin–oxygen adduct and oxygenating species (i.e., the flavin-N5-oxide) by mimicking a critical transition state. This study unambiguously demonstrates how enzymes may control the O2 functionalization of an organic cofactor as prerequisite for oxidative catalysis. Our work thus illustrates how O2 reactivity can be harnessed in an enzymatic environment and provides crucial knowledge for future rational design of O2-reactive enzymes.

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de Gonzalo, Gonzalo, and Andrés R. Alcántara. "Multienzymatic Processes Involving Baeyer–Villiger Monooxygenases." Catalysts 11, no. 5 (May 8, 2021): 605. http://dx.doi.org/10.3390/catal11050605.

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Baeyer–Villiger monooxygenases (BVMOs) are flavin-dependent oxidative enzymes capable of catalyzing the insertion of an oxygen atom between a carbonylic Csp2 and the Csp3 at the alpha position, therefore transforming linear and cyclic ketones into esters and lactones. These enzymes are dependent on nicotinamides (NAD(P)H) for the flavin reduction and subsequent reaction with molecular oxygen. BVMOs can be included in cascade reactions, coupled to other redox enzymes, such as alcohol dehydrogenases (ADHs) or ene-reductases (EREDs), so that the direct conversion of alcohols or α,β-unsaturated carbonylic compounds to the corresponding esters can be achieved. In the present review, the different synthetic methodologies that have been performed by employing multienzymatic strategies with BVMOs combining whole cells or isolated enzymes, through sequential or parallel methods, are described, with the aim of highlighting the advantages of performing multienzymatic systems, and show the recent advances for overcoming the drawbacks of using BVMOs in these techniques.

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Zhang, Jun-Jie, Hong Liu, Yi Xiao, Xian-En Zhang, and Ning-Yi Zhou. "Identification and Characterization of Catabolic para-Nitrophenol 4-Monooxygenase and para-Benzoquinone Reductase from Pseudomonas sp. Strain WBC-3." Journal of Bacteriology 191, no. 8 (February 13, 2009): 2703–10. http://dx.doi.org/10.1128/jb.01566-08.

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ABSTRACT Pseudomonas sp. strain WBC-3 utilizes para-nitrophenol (PNP) as a sole source of carbon, nitrogen, and energy. In order to identify the genes involved in this utilization, we cloned and sequenced a 12.7-kb fragment containing a conserved region of NAD(P)H:quinone oxidoreductase genes. Of the products of the 13 open reading frames deduced from this fragment, PnpA shares 24% identity to the large component of a 3-hydroxyphenylacetate hydroxylase from Pseudomonas putida U and PnpB is 58% identical to an NAD(P)H:quinone oxidoreductase from Escherichia coli. Both PnpA and PnpB were purified to homogeneity as His-tagged proteins, and they were considered to be a monomer and a dimer, respectively, as determined by gel filtration. PnpA is a flavin adenine dinucleotide-dependent single-component PNP 4-monooxygenase that converts PNP to para-benzoquinone in the presence of NADPH. PnpB is a flavin mononucleotide-and NADPH-dependent p-benzoquinone reductase that catalyzes the reduction of p-benzoquinone to hydroquinone. PnpB could enhance PnpA activity, and genetic analyses indicated that both pnpA and pnpB play essential roles in PNP mineralization in strain WBC-3. Furthermore, the pnpCDEF gene cluster next to pnpAB shares significant similarities with and has the same organization as a gene cluster responsible for hydroquinone degradation (hapCDEF) in Pseudomonas fluorescens ACB (M. J. Moonen, N. M. Kamerbeek, A. H. Westphal, S. A. Boeren, D. B. Janssen, M. W. Fraaije, and W. J. van Berkel, J. Bacteriol. 190:5190-5198, 2008), suggesting that the genes involved in PNP degradation are physically linked.

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Dick, Scott, Laura Marrone, Abraham M. Thariath, Miguel A. Valvano, and Thammaiah Viswanatha. "Cofactor- and substrate-binding domains in flavin-dependent N-hydroxylating enzymes." Trends in Biochemical Sciences 23, no. 11 (November 1998): 414. http://dx.doi.org/10.1016/s0968-0004(98)01271-7.

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Wang, Jinyu, and Yajun Liu. "Systematic Theoretical Study on the pH-Dependent Absorption and Fluorescence Spectra of Flavins." Molecules 28, no. 8 (April 8, 2023): 3315. http://dx.doi.org/10.3390/molecules28083315.

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Flavins are a class of organic compounds with the basic structure of 7,8-dimethy-10-alkyl isoalloxazine. They are ubiquitous in nature and participate in many biochemical reactions. Due to various existing forms, there is a lack of systematic research on the absorption and fluorescence spectra of flavins. In this study, employing the density functional theory (DFT) and time-dependent (TD) DFT, we calculated the pH-dependent absorption and fluorescence spectra of flavin of three redox states (quinone, semiquinone, and hydroquinone) in solvents. The chemical equilibrium of three redox states of flavins and the pH effect on the absorption spectra and fluorescence spectra of flavins were carefully discussed. The conclusion helps with identifying the existing forms of flavins in solvent with different pH values.

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Zverinsky, I. V., H. G. Zverinskaya, I. P. Sutsko, P. G. Telegin, and A. G. Shlyahtun. "Effects of berberine on the recovery of rat liver xenobiotic-metabolizing enzymes after partial hepatectomy." Biomeditsinskaya Khimiya 61, no. 3 (2015): 381–83. http://dx.doi.org/10.18097/pbmc20156103381.

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We have studied the effect of berberine on the recovery processes of liver xenobiotic-metabolizing function during its compensatory growth after 70% partial hepatectomy. It was found the hepatic ability to metabolize foreign substances are not restored up to day 8. Administration of berberine (10 mg/kg intraperitoneally) for 6 days led to normalization of both cytochrome P450-dependent and flavin-containing monooxygenases. It is suggested that in the biotransformation of berberine involved not only cytochrome P450, but also flavin-containing monooxygenases.

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McLEAN, Kirsty J., Nigel S. SCRUTTON, and Andrew W. MUNRO. "Kinetic, spectroscopic and thermodynamic characterization of the Mycobacterium tuberculosis adrenodoxin reductase homologue FprA." Biochemical Journal 372, no. 2 (June 1, 2003): 317–27. http://dx.doi.org/10.1042/bj20021692.

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The genome sequence of the pathogenic bacterium Mycobacterium tuberculosis revealed numerous cytochrome P450 enzymes, which require accessory redox enzymes for catalytic function (ferredoxin reductase and ferredoxin). The most likely ferredoxin reductase is encoded by fprA, and its structure resembles eukaryotic adrenodoxin reductases. We have cloned, expressed and purified the flavoenzyme product of the fprA gene in Escherichia coli. FprA reduces various electron acceptors using either NADPH or NADH as the electron donor, but discriminates in favour of NADPH (apparent Km for NADH=50.6±3.1 μM; NADPH=4.1±0.3 μM from ferricyanide reduction experiments). Stopped-flow studies of reduction of the FprA FAD by NADPH demonstrate increased flavin reduction rate at low NADPH concentration (<200 μM), consistent with the presence of a second, kinetically distinct and inhibitory, pyridine nucleotide-binding site, similar to that identified in human cytochrome P450 reductase [Gutierrez, Lian, Wolf, Scrutton and Roberts (2001) Biochemistry 40, 1964–1975]. Flavin reduction by NADH is slower than with NADPH and displays hyperbolic dependence on NADH concentration [maximal reduction rate (kred)=25.4±0.7 s−1, apparent Kd=42.9±4.6 μM]. Flavin reoxidation by molecular oxygen is more rapid for NADH-reduced enzyme. Reductive titrations show that the enzyme forms a species with spectral characteristics typical of a neutral (blue) FAD semiquinone only on reduction with NADPH, consistent with EPR studies. The second order dependence of semiquinone formation on the concentration of FprA indicates a disproportionation reaction involving oxidized and two-electron-reduced FprA. Titration of FprA with dithionite converts oxidized FAD into the hydroquinone form; the flavin semiquinone is not populated under these conditions. The midpoint reduction potential for the two electron couple is −235±5 mV (versus the normal hydrogen electrode), similar to that for adrenodoxin reductase (−274 mV). Our data provide a thermodynamic and transient kinetic framework for catalysis by FprA, and complement recent spectrophotometric and steady-state studies of the enzyme [Fischer, Raimondi, Aliverti and Zanetti (2002) Eur. J. Biochem. 269, 3005–3013].

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Huang, Yan, Randy Xun, Guanjun Chen, and Luying Xun. "Maintenance Role of a Glutathionyl-Hydroquinone Lyase (PcpF) in Pentachlorophenol Degradation by Sphingobium chlorophenolicum ATCC 39723." Journal of Bacteriology 190, no. 23 (September 26, 2008): 7595–600. http://dx.doi.org/10.1128/jb.00489-08.

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ABSTRACT Pentachlorophenol (PCP) is a toxic pollutant. Its biodegradation has been extensively studied in Sphingobium chlorophenolicum ATCC 39723. All enzymes required to convert PCP to a common metabolic intermediate before entering the tricarboxylic acid cycle have been characterized. One of the enzymes is tetrachloro-p-hydroquinone (TeCH) reductive dehalogenase (PcpC), which is a glutathione (GSH) S-transferase (GST). PcpC catalyzes the GSH-dependent conversion of TeCH to trichloro-p-hydroquinone (TriCH) and then to dichloro-p-hydroquinone (DiCH) in the PCP degradation pathway. PcpC is susceptible to oxidative damage, and the damaged PcpC produces glutathionyl (GS) conjugates, GS-TriCH and GS-DiCH, which cannot be further metabolized by PcpC. The fate and effect of GS-hydroquinone conjugates were unknown. A putative GST gene (pcpF) is located next to pcpC on the bacterial chromosome. The pcpF gene was cloned, and the recombinant PcpF was purified. The purified PcpF was able to convert GS-TriCH and GS-DiCH conjugates to TriCH and DiCH, respectively. The GS-hydroquinone lyase reactions catalyzed by PcpF are rather unusual for a GST. The disruption of pcpF in S. chlorophenolicum made the mutant lose the GS-hydroquinone lyase activities in the cell extracts. The mutant became more sensitive to PCP toxicity and had a significantly decreased PCP degradation rate, likely due to the accumulation of the GS-hydroquinone conjugates inside the cell. Thus, PcpF played a maintenance role in PCP degradation and converted the GS-hydroquinone conjugates back to the intermediates of the PCP degradation pathway.

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Wick, Jonas, Daniel Heine, Gerald Lackner, Mathias Misiek, James Tauber, Hans Jagusch, Christian Hertweck, and Dirk Hoffmeister. "A Fivefold Parallelized Biosynthetic Process Secures Chlorination of Armillaria mellea (Honey Mushroom) Toxins." Applied and Environmental Microbiology 82, no. 4 (December 11, 2015): 1196–204. http://dx.doi.org/10.1128/aem.03168-15.

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ABSTRACTThe basidiomycetous tree pathogenArmillaria mellea(honey mushroom) produces a large variety of structurally related antibiotically active and phytotoxic natural products, referred to as the melleolides. During their biosynthesis, some members of the melleolide family of compounds undergo monochlorination of the aromatic moiety, whose biochemical and genetic basis was not known previously. This first study on basidiomycete halogenases presents the biochemicalin vitrocharacterization of five flavin-dependentA. melleaenzymes (ArmH1 to ArmH5) that were heterologously produced inEscherichia coli. We demonstrate that all five enzymes transfer a single chlorine atom to the melleolide backbone. A 5-fold, secured biosynthetic step during natural product assembly is unprecedented. Typically, flavin-dependent halogenases are categorized into enzymes acting on free compounds as opposed to those requiring a carrier-protein-bound acceptor substrate. The enzymes characterized in this study clearly turned over free substrates. Phylogenetic clades of halogenases suggest that all fungal enzymes share an ancestor and reflect a clear divergence between ascomycetes and basidiomycetes.

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Neubauer, Pia R., Olga Blifernez-Klassen, Lara Pfaff, Mohamed Ismail, Olaf Kruse, and Norbert Sewald. "Two Novel, Flavin-Dependent Halogenases from the Bacterial Consortia of Botryococcus braunii Catalyze Mono- and Dibromination." Catalysts 11, no. 4 (April 10, 2021): 485. http://dx.doi.org/10.3390/catal11040485.

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Halogen substituents often lead to a profound effect on the biological activity of organic compounds. Flavin-dependent halogenases offer the possibility of regioselective halogenation at non-activated carbon atoms, while employing only halide salts and molecular oxygen. However, low enzyme activity, instability, and narrow substrate scope compromise the use of enzymatic halogenation as an economical and environmentally friendly process. To overcome these drawbacks, it is of tremendous interest to identify novel halogenases with high enzymatic activity and novel substrate scopes. Previously, Neubauer et al. developed a new hidden Markov model (pHMM) based on the PFAM tryptophan halogenase model, and identified 254 complete and partial putative flavin-dependent halogenase genes in eleven metagenomic data sets. In the present study, the pHMM was used to screen the bacterial associates of the Botryococcus braunii consortia (PRJEB21978), leading to the identification of several putative, flavin-dependent halogenase genes. Two of these new halogenase genes were found in one gene cluster of the Botryococcus braunii symbiont Sphingomonas sp. In vitro activity tests revealed that both heterologously expressed enzymes are active flavin-dependent halogenases able to halogenate indole and indole derivatives, as well as phenol derivatives, while preferring bromination over chlorination. Interestingly, SpH1 catalyses only monohalogenation, while SpH2 can catalyse both mono- and dihalogenation for some substrates.

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Andorfer, Mary C., and Jared C. Lewis. "Understanding and Improving the Activity of Flavin-Dependent Halogenases via Random and Targeted Mutagenesis." Annual Review of Biochemistry 87, no. 1 (June 20, 2018): 159–85. http://dx.doi.org/10.1146/annurev-biochem-062917-012042.

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Flavin-dependent halogenases (FDHs) catalyze the halogenation of organic substrates by coordinating reactions of reduced flavin, molecular oxygen, and chloride. Targeted and random mutagenesis of these enzymes have been used to both understand and alter their reactivity. These studies have led to insights into residues essential for catalysis and FDH variants with improved stability, expanded substrate scope, and altered site selectivity. Mutations throughout FDH structures have contributed to all of these advances. More recent studies have sought to rationalize the impact of these mutations on FDH function and to identify new FDHs to deepen our understanding of this enzyme class and to expand their utility for biocatalytic applications.

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Heine, Thomas, Willem van Berkel, George Gassner, Karl-Heinz van Pée, and Dirk Tischler. "Two-Component FAD-Dependent Monooxygenases: Current Knowledge and Biotechnological Opportunities." Biology 7, no. 3 (August 2, 2018): 42. http://dx.doi.org/10.3390/biology7030042.

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Flavoprotein monooxygenases create valuable compounds that are of high interest for the chemical, pharmaceutical, and agrochemical industries, among others. Monooxygenases that use flavin as cofactor are either single- or two-component systems. Here we summarize the current knowledge about two-component flavin adenine dinucleotide (FAD)-dependent monooxygenases and describe their biotechnological relevance. Two-component FAD-dependent monooxygenases catalyze hydroxylation, epoxidation, and halogenation reactions and are physiologically involved in amino acid metabolism, mineralization of aromatic compounds, and biosynthesis of secondary metabolites. The monooxygenase component of these enzymes is strictly dependent on reduced FAD, which is supplied by the reductase component. More and more representatives of two-component FAD-dependent monooxygenases have been discovered and characterized in recent years, which has resulted in the identification of novel physiological roles, functional properties, and a variety of biocatalytic opportunities.

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Pozzi, Cecilia, Ludovica Lopresti, Giusy Tassone, and Stefano Mangani. "Targeting Methyltransferases in Human Pathogenic Bacteria: Insights into Thymidylate Synthase (TS) and Flavin-Dependent TS (FDTS)." Molecules 24, no. 8 (April 25, 2019): 1638. http://dx.doi.org/10.3390/molecules24081638.

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In cells, thymidylate synthases provide the only de novo source of 2′-deoxythymidine-5′-monophosphate (dTMP), required for DNA synthesis. The activity of these enzymes is pivotal for cell survival and proliferation. Two main families of thymidylate synthases have been identified in bacteria, folate-dependent thymidylate synthase (TS) and flavin-dependent TS (FDTS). TS and FDTS are highly divergent enzymes, characterized by exclusive catalytic mechanisms, involving different sets of cofactors. TS and FDTS mechanisms of action have been recently revised, providing new perspectives for the development of antibacterial drugs targeting these enzymes. Nonetheless, some catalytic details still remain elusive. For bacterial TSs, half-site reactivity is still an open debate and the recent evidences are somehow controversial. Furthermore, different behaviors have been identified among bacterial TSs, compromising the definition of common mechanisms. Moreover, the redox reaction responsible for the regeneration of reduced flavin in FDTSs is not completely clarified. This review describes the recent advances in the structural and functional characterization of bacterial TSs and FDTSs and the current understanding of their mechanisms of action. Furthermore, the recent progresses in the development of inhibitors targeting TS and FDTS in human pathogenic bacteria are summarized.

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Biegasiewicz, Kyle F., Simon J. Cooper, Xin Gao, Daniel G. Oblinsky, Ji Hye Kim, Samuel E. Garfinkle, Leo A. Joyce, Braddock A. Sandoval, Gregory D. Scholes, and Todd K. Hyster. "Photoexcitation of flavoenzymes enables a stereoselective radical cyclization." Science 364, no. 6446 (June 20, 2019): 1166–69. http://dx.doi.org/10.1126/science.aaw1143.

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Photoexcitation is a common strategy for initiating radical reactions in chemical synthesis. We found that photoexcitation of flavin-dependent “ene”-reductases changes their catalytic function, enabling these enzymes to promote an asymmetric radical cyclization. This reactivity enables the construction of five-, six-, seven-, and eight-membered lactams with stereochemical preference conferred by the enzyme active site. After formation of a prochiral radical, the enzyme guides the delivery of a hydrogen atom from flavin—a challenging feat for small-molecule chemical reagents. The initial electron transfer occurs through direct excitation of an electron donor-acceptor complex that forms between the substrate and the reduced flavin cofactor within the enzyme active site. Photoexcitation of promiscuous flavoenzymes has thus furnished a previously unknown biocatalytic reaction.

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Fejzagić, Alexander Veljko, Jan Gebauer, Nikolai Huwa, and Thomas Classen. "Halogenating Enzymes for Active Agent Synthesis: First Steps Are Done and Many Have to Follow." Molecules 24, no. 21 (November 5, 2019): 4008. http://dx.doi.org/10.3390/molecules24214008.

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Halogens can be very important for active agents as vital parts of their binding mode, on the one hand, but are on the other hand instrumental in the synthesis of most active agents. However, the primary halogenating compound is molecular chlorine which has two major drawbacks, high energy consumption and hazardous handling. Nature bypassed molecular halogens and evolved at least six halogenating enzymes: Three kind of haloperoxidases, flavin-dependent halogenases as well as α-ketoglutarate and S-adenosylmethionine (SAM)-dependent halogenases. This review shows what is known today on these enzymes in terms of biocatalytic usage. The reader may understand this review as a plea for the usage of halogenating enzymes for fine chemical syntheses, but there are many steps to take until halogenating enzymes are reliable, flexible, and sustainable catalysts for halogenation.

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Pimviriyakul, Panu, Panida Surawatanawong, and Pimchai Chaiyen. "Oxidative dehalogenation and denitration by a flavin-dependent monooxygenase is controlled by substrate deprotonation." Chemical Science 9, no. 38 (2018): 7468–82. http://dx.doi.org/10.1039/c8sc01482e.

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Willetts, Andrew. "The Isoenzymic Diketocamphane Monooxygenases of Pseudomonas putida ATCC 17453—An Episodic History and Still Mysterious after 60 Years." Microorganisms 9, no. 12 (December 15, 2021): 2593. http://dx.doi.org/10.3390/microorganisms9122593.

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Researching the involvement of molecular oxygen in the degradation of the naturally occurring bicyclic terpene camphor has generated a six-decade history of fascinating monooxygenase biochemistry. While an extensive bibliography exists reporting the many varied studies on camphor 5-monooxygenase, the initiating enzyme of the relevant catabolic pathway in Pseudomonas putida ATCC 17453, the equivalent recorded history of the isoenzymic diketocamphane monooxygenases, the enzymes that facilitate the initial ring cleavage of the bicyclic terpene, is both less extensive and more enigmatic. First referred to as ‘ketolactonase—an enzyme for cyclic lactonization’—the enzyme now classified as 2,5-diketocamphane 1,2-monooxygenase (EC 1.14.14.108) holds a special place in the history of oxygen-dependent biochemistry, being the first biocatalyst confirmed to undertake a biooxygenation reaction equivalent to the peracid-catalysed Baeyer–Villiger chemical oxidation first reported in the late 19th century. However, following that auspicious beginning, the biochemistry of EC 1.14.14.108, and its isoenzymic partner 3,6-diketocamphane 1,6-monooxygenase (EC 1.14.14.155) was dogged for many years by the mistaken belief that the enzymes were true flavoproteins that function with a tightly-bound flavin cofactor in the active site. This misconception led to a number of erroneous interpretations of relevant experimental data. It is only in the last decade, initially as the result of pure serendipity, that these enzymes have been confirmed to be members of a relatively recently discovered class of oxygen-dependent enzymes, the flavin-dependent two-component monooxygenases. This has promoted a renaissance of interest in the enzymes, resulting in programmes of research that have significantly expanded current knowledge of both their mode of action and regulation in camphor-grown P. putida ATCC 17453. However, some features of the biochemistry of the isoenzymic diketocamphane monooxygenases remain currently unexplained. It is the episodic history of these enzymes and some of what remains unresolved that are the principal subjects of this review.

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Ung, Kien Lam, Chloé Poussineau, Julie Couston, Husam M. A. B. Alsarraf, and Mickaël Blaise. "Crystal structure of MAB_4123, a putative flavin-dependent monooxygenase from Mycobacterium abscessus." Acta Crystallographica Section F Structural Biology Communications 79, no. 5 (May 1, 2023): 128–36. http://dx.doi.org/10.1107/s2053230x2300345x.

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Numerous bacteria from different phylae can perform desulfurization reactions of organosulfur compounds. In these degradation or detoxification pathways, two-component flavin-dependent monooxygenases that use flavins (FMN or FAD) as a cofactor play important roles as they catalyse the first steps of these metabolic routes. The TdsC or DszC and MsuC proteins belong to this class of enzymes as they process dibenzothiophene (DBT) and methanesulfinate. Elucidation of their X-ray structures in apo, ligand-bound and cofactor-bound forms has provided important molecular insights into their catalytic reaction. Mycobacterial species have also been shown to possess a DBT degradation pathway, but no structural information is available on these two-component flavin-dependent monooxygenases. In this study, the crystal structure of the uncharacterized MAB_4123 protein from the human pathogen Mycobacterium abscessus is presented. The structure solved at high resolution displays high similarity to homologs from Rhodococcus, Paenibacillus and Pseudomonas species. In silico docking approaches suggest that MAB_4123 binds FMN and may use it as a cofactor. Structural analysis strongly suggests that MAB_4123 is a two-component flavin-dependent monooxygenase that could act as a detoxifying enzyme of organosulfur compounds in mycobacteria.

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Pimviriyakul, Panu, and Pimchai Chaiyen. "A complete bioconversion cascade for dehalogenation and denitration by bacterial flavin–dependent enzymes." Journal of Biological Chemistry 293, no. 48 (October 3, 2018): 18525–39. http://dx.doi.org/10.1074/jbc.ra118.005538.

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Shah, Mihir V., James Antoney, Suk Woo Kang, Andrew C. Warden, Carol J. Hartley, Hadi Nazem-Bokaee, Colin J. Jackson, and Colin Scott. "Cofactor F420-Dependent Enzymes: An Under-Explored Resource for Asymmetric Redox Biocatalysis." Catalysts 9, no. 10 (October 20, 2019): 868. http://dx.doi.org/10.3390/catal9100868.

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The asymmetric reduction of enoates, imines and ketones are among the most important reactions in biocatalysis. These reactions are routinely conducted using enzymes that use nicotinamide cofactors as reductants. The deazaflavin cofactor F420 also has electrochemical properties that make it suitable as an alternative to nicotinamide cofactors for use in asymmetric reduction reactions. However, cofactor F420-dependent enzymes remain under-explored as a resource for biocatalysis. This review considers the cofactor F420-dependent enzyme families with the greatest potential for the discovery of new biocatalysts: the flavin/deazaflavin-dependent oxidoreductases (FDORs) and the luciferase-like hydride transferases (LLHTs). The characterized F420-dependent reductions that have the potential for adaptation for biocatalysis are discussed, and the enzymes best suited for use in the reduction of oxidized cofactor F420 to allow cofactor recycling in situ are considered. Further discussed are the recent advances in the production of cofactor F420 and its functional analog FO-5′-phosphate, which remains an impediment to the adoption of this family of enzymes for industrial biocatalytic processes. Finally, the prospects for the use of this cofactor and dependent enzymes as a resource for industrial biocatalysis are discussed.

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Capeillère-Blandin, C., M. J. Barber, and R. C. Bray. "Comparison of the processes involved in reduction by the substrate for two homologous flavocytochromes b2 from different species of yeast." Biochemical Journal 238, no. 3 (September 15, 1986): 745–56. http://dx.doi.org/10.1042/bj2380745.

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A detailed study of the electron exchanges involved between FMN and haem b2 groups within flavocytochrome b2 of yeast Hansenula anomala (H-enzyme) was performed. The results were compared with those for the homologous enzyme of yeast Saccharomyces cerevisiae (Sx-enzyme) re-investigated at 5 degrees C. The mid-point reduction potentials of FMN and haem were determined by two complementary methods: potentiometric titration with substrate, L-lactate, in the presence of dye mediators with quantification of the reduced species performed by spectrophotometry at suitable wavelengths; anaerobic titration of the enzyme by its substrate by monitoring the e.p.r. signals of the semiquinone and Fe3+ species. Values of Em,7 = -19, -23 and -45 V were determined respectively from the data for the three redox systems Ho/Hr, Fo/Fsq and Fsq/Fr in the H-enzyme instead of +6, -44 and -57 mV respectively in the Sx-enzyme [Capeillère-Blandin, Bray, Iwatsubo & Labeyrie (1975) Eur. J. Biochem. 54, 549-566]. Parallel e.p.r rapid-freezing and absorbance stopped-flow studies allowed determination of the time courses of the various redox species during their reduction by L-lactate. The flavin and the haem reduction time courses were biphasic. In the initial fast phase the reduction of flavin monitored by absorbance measurements is accomplished with a rate constant kF = 360 s-1. The reduction of the haem lags the reduction of flavin with a rate constant kH = 170 s-1. The appearance of flavin free radical is slower than the reduction in flavin absorbance and occurs with a rate constant close to that of the reduction of the haem. At saturating L-lactate concentration the initial rapid phase (up to 15 ms) involved in the overall turnover can be adequately simulated with a two-step reaction scheme. The main difference between the enzymes lies especially at the level of the first step of electron exchange between bound lactate and flavin, which for the H-enzyme is no longer the rate-limiting step in the haem reduction and becomes 8-fold faster than in the Sx-enzyme. Consequently in the H-enzyme for the following step, the intramolecular transfer from flavin hydroquinone to oxidized haem, a reliable evaluation of the rate constants becomes possible. Preliminary values are k+2 = 380 s-1 and k-2 = 120 s-1 at 5 degrees C.(ABSTRACT TRUNCATED AT 400 WORDS)

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Ferreira, Maria Isabel M., Toshiya Iida, Syed A. Hasan, Kaoru Nakamura, Marco W. Fraaije, Dick B. Janssen, and Toshiaki Kudo. "Analysis of Two Gene Clusters Involved in the Degradation of 4-Fluorophenol by Arthrobacter sp. Strain IF1." Applied and Environmental Microbiology 75, no. 24 (October 16, 2009): 7767–73. http://dx.doi.org/10.1128/aem.00171-09.

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ABSTRACT Arthrobacter sp. strain IF1 is able to grow on 4-fluorophenol (4-FP) as a sole source of carbon and energy. To clone the 4-FP degradation genes, DNA libraries were constructed and screened with a probe obtained by PCR using primers designed on the basis of conserved regions of aromatic two-component monooxygenases. Sequencing of positive clones yielded two gene clusters, each harboring a gene encoding a monooxygenase with high sequence similarity to the oxygenase component of 4-nitrophenol and 4-chlorophenol monooxygenase systems. Both these monooxygenase genes were differentially expressed during growth on 4-FP, as revealed by Northern blotting and reverse transcription-PCR. One cluster also contained a gene for a flavin reductase. The monooxygenase and reductase were purified from Escherichia coli cells expressing the corresponding genes, and together they catalyzed NADH-dependent hydroxylation and dehalogenation of 4-halophenols. The results indicate that strain IF1 transforms 4-FP to hydroquinone by a two-component monooxygenase system of which one component provides reduced flavin adenine dinucleotide at the expense of NADH and the other catalyzes para-hydroxylation of 4-FP and other 4-substituted phenols.

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Deng, Yaming, Quan Zhou, Yuzhou Wu, Xi Chen, and Fangrui Zhong. "Properties and Mechanisms of Flavin-Dependent Monooxygenases and Their Applications in Natural Product Synthesis." International Journal of Molecular Sciences 23, no. 5 (February 27, 2022): 2622. http://dx.doi.org/10.3390/ijms23052622.

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Natural products are usually highly complicated organic molecules with special scaffolds, and they are an important resource in medicine. Natural products with complicated structures are produced by enzymes, and this is still a challenging research field, its mechanisms requiring detailed methods for elucidation. Flavin adenine dinucleotide (FAD)-dependent monooxygenases (FMOs) catalyze many oxidation reactions with chemo-, regio-, and stereo-selectivity, and they are involved in the synthesis of many natural products. In this review, we introduce the mechanisms for different FMOs, with the classical FAD (C4a)-hydroperoxide as the major oxidant. We also summarize the difference between FMOs and cytochrome P450 (CYP450) monooxygenases emphasizing the advantages of FMOs and their specificity for substrates. Finally, we present examples of FMO-catalyzed synthesis of natural products. Based on these explanations, this review will expand our knowledge of FMOs as powerful enzymes, as well as implementation of the FMOs as effective tools for biosynthesis.

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Chanda, Kakoli, Atifa Begum Mozumder, Ringhoilal Chorei, Ridip Kumar Gogoi, and Himanshu Kishore Prasad. "A Lignocellulolytic Colletotrichum sp. OH with Broad-Spectrum Tolerance to Lignocellulosic Pretreatment Compounds and Derivatives and the Efficiency to Produce Hydrogen Peroxide and 5-Hydroxymethylfurfural Tolerant Cellulases." Journal of Fungi 7, no. 10 (September 22, 2021): 785. http://dx.doi.org/10.3390/jof7100785.

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Fungal endophytes are an emerging source of novel traits and biomolecules suitable for lignocellulosic biomass treatment. This work documents the toxicity tolerance of Colletotrichum sp. OH toward various lignocellulosic pretreatment-derived inhibitors. The effects of aldehydes (vanillin, p-hydroxybenzaldehyde, furfural, 5-hydroxymethylfurfural; HMF), acids (gallic, formic, levulinic, and p-hydroxybenzoic acid), phenolics (hydroquinone, p-coumaric acid), and two pretreatment chemicals (hydrogen peroxide and ionic liquid), on the mycelium growth, biomass accumulation, and lignocellulolytic enzyme activities, were tested. The reported Colletotrichum sp. OH was naturally tolerant to high concentrations of single inhibitors like HMF (IC50; 17.5 mM), levulinic acid (IC50; 29.7 mM), hydroquinone (IC50; 10.76 mM), and H2O2 (IC50; 50 mM). The lignocellulolytic enzymes displayed a wide range of single and mixed inhibitor tolerance profiles. The enzymes β-glucosidase and endoglucanase showed H2O2- and HMF-dependent activity enhancements. The enzyme β-glucosidase activity was 34% higher in 75 mM and retained 20% activity in 125 mM H2O2. Further, β-glucosidase activity increased to 24 and 32% in the presence of 17.76 and 8.8 mM HMF. This research suggests that the Colletotrichum sp. OH, or its enzymes, can be used to pretreat plant biomass, hydrolyze it, and remove inhibitory by-products.

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Manenda, Mahder S., Marie-Ève Picard, Liping Zhang, Normand Cyr, Xiaojun Zhu, Julie Barma, John M. Pascal, Manon Couture, Changsheng Zhang, and Rong Shi. "Structural analyses of the Group A flavin-dependent monooxygenase PieE reveal a sliding FAD cofactor conformation bridging OUT and IN conformations." Journal of Biological Chemistry 295, no. 14 (February 28, 2020): 4709–22. http://dx.doi.org/10.1074/jbc.ra119.011212.

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Group A flavin-dependent monooxygenases catalyze the cleavage of the oxygen–oxygen bond of dioxygen, followed by the incorporation of one oxygen atom into the substrate molecule with the aid of NADPH and FAD. These flavoenzymes play an important role in many biological processes, and their most distinct structural feature is the choreographed motions of flavin, which typically adopts two distinct conformations (OUT and IN) to fulfill its function. Notably, these enzymes seem to have evolved a delicate control system to avoid the futile cycle of NADPH oxidation and FAD reduction in the absence of substrate, but the molecular basis of this system remains elusive. Using protein crystallography, size-exclusion chromatography coupled to multi-angle light scattering (SEC-MALS), and small-angle X-ray scattering (SEC-SAXS) and activity assay, we report here a structural and biochemical characterization of PieE, a member of the Group A flavin-dependent monooxygenases involved in the biosynthesis of the antibiotic piericidin A1. This analysis revealed that PieE forms a unique hexamer. Moreover, we found, to the best of our knowledge for the first time, that in addition to the classical OUT and IN conformations, FAD possesses a “sliding” conformation that exists in between the OUT and IN conformations. This observation sheds light on the underlying mechanism of how the signal of substrate binding is transmitted to the FAD-binding site to efficiently initiate NADPH binding and FAD reduction. Our findings bridge a gap currently missing in the orchestrated order of chemical events catalyzed by this important class of enzymes.

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Ogawa, Aoba, Gen-ichi Sampei, and Gota Kawai. "Crystal structure of the flavin-dependent thymidylate synthase Thy1 from Thermus thermophilus with an extra C-terminal domain." Acta Crystallographica Section F Structural Biology Communications 75, no. 6 (June 1, 2019): 450–54. http://dx.doi.org/10.1107/s2053230x19007192.

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The thymidylate synthases ThyA and Thy1 are enzymes that catalyse the formation of thymidine monophosphate from 2′-deoxyuridine monophosphate. Thy1 (or ThyX) requires flavin for catalytic reactions, while ThyA does not. In the present study, the crystal structure of the flavin-dependent thymidylate synthase Thy1 from Thermus thermophilus HB8 (TtThy1, TTHA1096) was determined in complex with FAD and phosphate at 2.5 Å resolution. TtThy1 is a tetrameric molecule like other Thy1 proteins, to which four FAD molecules are bound. In the crystal of TtThy1, two phosphate ions were bound to each dUMP-binding site. The characteristic feature of TtThy1 is the existence of an extra C-terminal domain (CTD) consisting of three α-helices and a β-strand. The function of the CTD is unknown and database analysis showed that this CTD is only shared by part of the Deinococcus–Thermus phylum.

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Mączka, Wanda, Katarzyna Wińska, and Małgorzata Grabarczyk. "Biotechnological Methods of Sulfoxidation: Yesterday, Today, Tomorrow." Catalysts 8, no. 12 (December 5, 2018): 624. http://dx.doi.org/10.3390/catal8120624.

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The production of chiral sulphoxides is an important part of the chemical industry since they have been used not only as pharmaceuticals and pesticides, but also as catalysts or functional materials. The main purpose of this review is to present biotechnological methods for the oxidation of sulfides. The work consists of two parts. In the first part, examples of biosyntransformation of prochiral sulfides using whole cells of bacteria and fungi are discussed. They have more historical significance due to the low predictability of positive results in relation to the workload. In the second part, the main enzymes responsible for sulfoxidation have been characterized such as chloroperoxidase, dioxygenases, cytochrome flavin-dependent monooxygenases, and P450 monooxygenases. Particular emphasis has been placed on the huge variety of cytochrome P450 monooxygenases, and flavin-dependent monooxygenases, which allows for pure sulfoxides enantiomers effectively to be obtained. In the summary, further directions of research on the optimization of enzymatic sulfoxidation are indicated.

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Buss, Maren, Christina Geerds, Thomas Patschkowski, Karsten Niehaus, and Hartmut H. Niemann. "Perfect merohedral twinning combined with noncrystallographic symmetry potentially causes the failure of molecular replacement with low-homology search models for the flavin-dependent halogenase HalX from Xanthomonas campestris." Acta Crystallographica Section F Structural Biology Communications 74, no. 6 (May 18, 2018): 345–50. http://dx.doi.org/10.1107/s2053230x18006933.

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Flavin-dependent halogenases can be used as biocatalysts because they regioselectively halogenate their substrates under mild reaction conditions. New halogenases with novel substrate specificities will add to the toolbox of enzymes available to organic chemists. HalX, the product of the xcc-b100_4193 gene, is a putative flavin-dependent halogenase from Xanthomonas campestris. The enzyme was recombinantly expressed and crystallized in order to aid in identifying its hitherto unknown substrate. Native data collected to a resolution of 2.5 Å showed indications of merohedral twinning in a hexagonal lattice. Attempts to solve the phase problem by molecular replacement failed. Here, a detailed analysis of the suspected twinning is presented. It is most likely that the crystals are trigonal (point group 3) and exhibit perfect hemihedral twinning so that they appear to be hexagonal (point group 6). As there are several molecules in the asymmetric unit, noncrystallographic symmetry may complicate twinning analysis and structure determination.

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Matsubara, Toshiyuki, Takashi Ohshiro, Yoshihiro Nishina, and Yoshikazu Izumi. "Purification, Characterization, and Overexpression of Flavin Reductase Involved in Dibenzothiophene Desulfurization byRhodococcus erythropolis D-1." Applied and Environmental Microbiology 67, no. 3 (March 1, 2001): 1179–84. http://dx.doi.org/10.1128/aem.67.3.1179-1184.

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ABSTRACT The dibenzothiophene (DBT)-desulfurizing bacterium,Rhodococcus erythropolis D-1, removes sulfur from DBT to form 2-hydroxybiphenyl using four enzymes, DszC, DszA, DszB, and flavin reductase. In this study, we purified and characterized the flavin reductase from R. erythropolis D-1 grown in a medium containing DBT as the sole source of sulfur. It is conceivable that the enzyme is essential for two monooxygenase (DszC and DszA) reactions in vivo. The purified flavin reductase contains no chromogenic cofactors and was found to have a molecular mass of 86 kDa and four identical 22-kDa subunits. The enzyme catalyzed NADH-dependent reduction of flavin mononucleotide (FMN), and the Km values for NADH and FMN were 208 and 10.8 μM, respectively. Flavin adenine dinucleotide was a poor substrate, and NADPH was inert. The enzyme did not catalyze reduction of any nitroaromatic compound. The optimal temperature and optimal pH for enzyme activity were 35°C and 6.0, respectively, and the enzyme retained 30% of its activity after heat treatment at 80°C for 30 min. The N-terminal amino acid sequence of the purified flavin reductase was identical to that of DszD of R. erythropolis IGTS8 (K. A. Gray, O. S. Pogrebinsky, G. T. Mrachko, L. Xi, D. J. Monticello, and C. H. Squires, Nat. Biotechnol. 14:1705–1709, 1996). The flavin reductase gene was amplified with primers designed by using dszD ofR. erythropolis IGTS8, and the enzyme was overexpressed inEscherichia coli. The specific activity in crude extracts of the overexpressed strain was about 275-fold that of the wild-type strain.

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Williams, Richard E., Deborah A. Rathbone, Nigel S. Scrutton, and Neil C. Bruce. "Biotransformation of Explosives by the Old Yellow Enzyme Family of Flavoproteins." Applied and Environmental Microbiology 70, no. 6 (June 2004): 3566–74. http://dx.doi.org/10.1128/aem.70.6.3566-3574.2004.

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ABSTRACT Several independent studies of bacterial degradation of nitrate ester explosives have demonstrated the involvement of flavin-dependent oxidoreductases related to the old yellow enzyme (OYE) of yeast. Some of these enzymes also transform the nitroaromatic explosive 2,4,6-trinitrotoluene (TNT). In this work, catalytic capabilities of five members of the OYE family were compared, with a view to correlating structure and function. The activity profiles of the five enzymes differed substantially; no one compound proved to be a good substrate for all five enzymes. TNT is reduced, albeit slowly, by all five enzymes. The nature of the transformation products differed, with three of the five enzymes yielding products indicative of reduction of the aromatic ring. Our findings suggest two distinct pathways of TNT transformation, with the initial reduction of TNT being the key point of difference between the enzymes. Characterization of an active site mutant of one of the enzymes suggests a structural basis for this difference.

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Messiha, Hanan L., Thanyaporn Wongnate, Pimchai Chaiyen, Alex R. Jones, and Nigel S. Scrutton. "Magnetic field effects as a result of the radical pair mechanism are unlikely in redox enzymes." Journal of The Royal Society Interface 12, no. 103 (February 2015): 20141155. http://dx.doi.org/10.1098/rsif.2014.1155.

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Environmental exposure to electromagnetic fields is potentially carcinogenic. The radical pair mechanism is considered the most feasible mechanism of interaction between weak magnetic fields encountered in our environment and biochemical systems. Radicals are abundant in biology, both as free radicals and reaction intermediates in enzyme mechanisms. The catalytic cycles of some flavin-dependent enzymes are either known or potentially involve radical pairs. Here, we have investigated the magnetic field sensitivity of a number of flavoenzymes with important cellular roles. We also investigated the magnetic field sensitivity of a model system involving stepwise reduction of a flavin analogue by a nicotinamide analogue—a reaction known to proceed via a radical pair. Under the experimental conditions used, magnetic field sensitivity was not observed in the reaction kinetics from stopped-flow measurements in any of the systems studied. Although widely implicated in radical pair chemistry, we conclude that thermally driven, flavoenzyme-catalysed reactions are unlikely to be influenced by exposure to external magnetic fields.

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Kassay, Norbert, Vanda Toldi, József Tőzsér, and András Szabó. "Cigarette smoke toxin hydroquinone and misfolding pancreatic lipase variant cooperatively promote endoplasmic reticulum stress and cell death." PLOS ONE 17, no. 6 (June 15, 2022): e0269936. http://dx.doi.org/10.1371/journal.pone.0269936.

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Mutation-induced protein misfolding of pancreatic secretory enzymes and consequent endoplasmic reticulum stress can cause chronic pancreatitis. A recent study revealed that cigarette smoke also increases the risk of the disease through endoplasmic reticulum stress. Here, we investigated the cumulative cellular effect of the G233E misfolding human pancreatic lipase variant and hydroquinone; a main toxic constituent of cigarette smoke, using mammalian cell lines. We found that hydroquinone reduces cell viability on a dose-dependent manner through programmed cell death, and diminishes lipase secretion without affecting its expression. Interestingly, hydroquinone decreased the viability more markedly in cells expressing the G233E lipase variant, than in cells producing wild-type lipase. The more substantial viability loss was due to increased endoplasmic reticulum stress, as demonstrated by elevated levels of X-box binding protein 1 mRNA splicing and immunoglobulin binding protein, NAD(P)H:quinone oxidoreductase 1 and C/EBP homologous protein expression. Unresolved endoplasmic reticulum stress, and especially up-regulation of the pro-apoptotic transcription factor C/EBP homologous protein were likely responsible for the increased cell death. Our observations demonstrated that the combination of hydroquinone and misfolding pancreatic lipase variant promote increased levels of endoplasmic reticulum stress and cell death, which may predispose to chronic pancreatitis.

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Spohn, Gabriele, Andre Kleinridders, F. Thomas Wunderlich, Matthias Watzka, Frank Zaucke, Katrin Blum-bach, Christof Geisen, et al. "VKORC1 deficiency in mice causes early postnatal lethality due to severe bleeding." Thrombosis and Haemostasis 101, no. 06 (2009): 1044–50. http://dx.doi.org/10.1160/th09-03-0204.

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SummaryVitamin K hydroquinone is oxidised to the epoxide form (K>O) during vitamin K-dependent posttranslational γ-glutamyl carboxylation resulting in biological active so called vitamin K-dependent proteins. In turn, K>O is reduced by the enzyme VKORC1 (vitamin K epoxide reductase complex component 1) to complete the vitamin K cycle. To investigate the biological role of VKORC1 in vivo, we generated VKORC1 knockout mice. Homozygous VKORC1-deficient mice developed normally until birth. Within 2–20 days after birth, the knockout mice died due to extensive, predominantly intracerebral haemorrhage. Bleeding resulted from a severe deficiency of γ-carboxylated clotting factors. This lethal phenotype could be rescued by oral administration of vitamin K. Additionally, morphometric analysis of the limbs in VKORC1-deficient animals revealed reduced length of bone calcification relative to wild-type control mice. The observed phenotype of VKORC1 knockout mice excludes the existence of other enzymes with VKOR activity that can substitute to supply vitamin K hydroquinone required for maturation of blood clotting factors. Thus, our study underscores the essential role of VKORC1 in vitamin K-dependent γ-glutamyl carboxylation.

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Roberts, Kenneth M., José R. Tormos, and Paul F. Fitzpatrick. "Characterization of Unstable Products of Flavin- and Pterin-Dependent Enzymes by Continuous-Flow Mass Spectrometry." Biochemistry 53, no. 16 (April 18, 2014): 2672–79. http://dx.doi.org/10.1021/bi500267c.

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Dzeja, Petras P., Peter Bast, Cevher Ozcan, Arturo Valverde, Ekshon L. Holmuhamedov, David G. L. Van Wylen, and Andre Terzic. "Targeting nucleotide-requiring enzymes: implications for diazoxide-induced cardioprotection." American Journal of Physiology-Heart and Circulatory Physiology 284, no. 4 (April 1, 2003): H1048—H1056. http://dx.doi.org/10.1152/ajpheart.00847.2002.

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Modulation of mitochondrial respiratory chain, dehydrogenase, and nucleotide-metabolizing enzyme activities is fundamental to cellular protection. Here, we demonstrate that the potassium channel opener diazoxide, within its cardioprotective concentration range, modulated the activity of flavin adenine dinucleotide-dependent succinate dehydrogenase with an IC50 of 32 μM and reduced the rate of succinate-supported generation of reactive oxygen species (ROS) in heart mitochondria. 5-Hydroxydecanoic fatty acid circumvented diazoxide-inhibited succinate dehydrogenase-driven electron flow, indicating a metabolism-dependent supply of redox equivalents to the respiratory chain. In perfused rat hearts, diazoxide diminished the generation of malondialdehyde, a marker of oxidative stress, which, however, increased on diazoxide washout. This effect of diazoxide mimicked ischemic preconditioning and was associated with reduced oxidative damage on ischemia-reperfusion. Diazoxide reduced cellular and mitochondrial ATPase activities, along with nucleotide degradation, contributing to preservation of myocardial ATP levels during ischemia. Thus, by targeting nucleotide-requiring enzymes, particularly mitochondrial succinate dehydrogenase and cellular ATPases, diazoxide reduces ROS generation and nucleotide degradation, resulting in preservation of myocardial energetics under stress.

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Zografos, Alexandros, and Marina Petsi. "Advances in Catalytic Aerobic Oxidations by Activation of Dioxygen-Monooxygenase Enzymes and Biomimetics." Synthesis 50, no. 24 (October 15, 2018): 4715–45. http://dx.doi.org/10.1055/s-0037-1610297.

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Monooxygenases are not only some of the most versatile machineries in our lives, but also some of the most explored enzymes in modern organic synthesis. They provide knowledge and inspiration on how the most abandoned oxidant, dioxygen, can be activated and utilized to deliver selective oxidations. This review presents an outline in the mechanisms that Nature uses to succeed in these processes and recent indicative examples on how chemists use this knowledge to develop selective oxidation protocols based on dioxygen as the terminal oxidant.1 Introduction2 Monooxygenases2.1 Metal-Based Monooxygenases2.1.1 Cytochromes2.1.2 Copper-Dependent Monooxygenases2.1.3 Heme-Independent Iron Monooxygenases2.1.4 Pterin-Dependent Monooxygenases2.2 Metal-Free Monooxygenases2.2.1 Flavin-Dependent Monooxygenases2.2.2 Systems without Cofactors3 Biomimetic Aerobic Oxidations3.1 Aerobic Oxidations Based on Metal Catalysts3.1.1 Epoxidations and Allylic Oxidations3.1.2 Oxidations of Unactivated Carbon Atoms and Benzylic Oxidations3.1.3 Oxidations of Aryl Groups3.1.4 Heteroatom Oxidations3.2 Aerobic Oxidations Based on Organocatalysts3.2.1 Baeyer–Villiger Oxidations3.2.2 Oxidations of Aryl Groups3.2.3 Heteroatom Oxidations4 Conclusion

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Gorlatova, Natalia, Marek Tchorzewski, Tatsuo Kurihara, Kenji Soda, and Nobuyoshi Esaki. "Purification, Characterization, and Mechanism of a Flavin Mononucleotide-Dependent 2-Nitropropane Dioxygenase fromNeurospora crassa." Applied and Environmental Microbiology 64, no. 3 (March 1, 1998): 1029–33. http://dx.doi.org/10.1128/aem.64.3.1029-1033.1998.

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ABSTRACT A nitroalkane-oxidizing enzyme was purified to homogeneity fromNeurospora crassa. The enzyme is composed of two subunits; the molecular weight of each subunit is approximately 40,000. The enzyme catalyzes the oxidation of nitroalkanes to produce the corresponding carbonyl compounds. It acts on 2-nitropropane better than on nitroethane and 1-nitropropane, and anionic forms of nitroalkanes are much better substrates than are neutral forms. The enzyme does not act on aromatic compounds. When the enzyme reaction was conducted in an18O2 atmosphere with the anionic form of 2-nitropropane as the substrate, acetone (with a molecular mass of 60 Da) was produced. This indicates that the oxygen atom of acetone was derived from molecular oxygen, not from water; hence, the enzyme is an oxygenase. The reaction stoichiometry was 2CH3CH(NO2)-CH3 + O2→2CH3COCH3 + 2HNO2, which is identical to that of the reaction of 2-nitropropane dioxygenase from Hansenula mrakii. The reaction of theNeurospora enzyme was inhibited by superoxide anion scavengers in the same manner as that of the Hansenulaenzyme. Both of these enzymes are flavoenzymes; however, theNeurospora enzyme contains flavin mononucleotide as a prosthetic group, whereas the Hansenula enzyme contains flavin adenine dinucleotide.

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Gao, Jinmin, Liyuan Li, Shijie Shen, Guomin Ai, Bin Wang, Fang Guo, Tongjian Yang, et al. "Cofactor-independent C–C bond cleavage reactions catalyzed by the AlpJ family of oxygenases in atypical angucycline biosynthesis." Beilstein Journal of Organic Chemistry 20 (May 23, 2024): 1198–206. http://dx.doi.org/10.3762/bjoc.20.102.

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Biosynthesis of atypical angucyclines involves unique oxidative B-ring cleavage and rearrangement reactions, which are catalyzed by AlpJ-family oxygenases, including AlpJ, JadG, and GilOII. Prior investigations established the essential requirement for FADH2/FMNH2 as cofactors when utilizing the quinone intermediate dehydrorabelomycin as a substrate. In this study, we unveil a previously unrecognized facet of these enzymes as cofactor-independent oxygenases when employing the hydroquinone intermediate CR1 as a substrate. The enzymes autonomously drive oxidative ring cleavage and rearrangement reactions of CR1, yielding products identical to those observed in cofactor-dependent reactions of AlpJ-family oxygenases. Furthermore, the AlpJ- and JadG-catalyzed reactions of CR1 could be quenched by superoxide dismutase, supporting a catalytic mechanism wherein the substrate CR1 reductively activates molecular oxygen, generating a substrate radical and the superoxide anion O2•−. Our findings illuminate a substrate-controlled catalytic mechanism of AlpJ-family oxygenases, expanding the realm of cofactor-independent oxygenases. Notably, AlpJ-family oxygenases stand as a pioneering example of enzymes capable of catalyzing oxidative reactions in either an FADH2/FMNH2-dependent or cofactor-independent manner.

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Chamizo-Ampudia, Alejandro, Aurora Galvan, Emilio Fernandez, and Angel Llamas. "The Chlamydomonas reinhardtii Molybdenum Cofactor Enzyme crARC Has a Zn-Dependent Activity and Protein Partners Similar to Those of Its Human Homologue." Eukaryotic Cell 10, no. 10 (July 29, 2011): 1270–82. http://dx.doi.org/10.1128/ec.05096-11.

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ABSTRACT The ARC (amidoxime reducing component) proteins are molybdenum cofactor (Moco) enzymes named hmARC1 and hmARC2 (human ARCs [hmARCs]) in humans and YcbX in Escherichia coli. They catalyze the reduction of a broad range of N-hydroxylated compounds (NHC) using reducing power supplied by other proteins. Some NHC are prodrugs or toxic compounds. YcbX contains a ferredoxin (Fd) domain and requires the NADPH flavin reductase CysJ to reduce NHC. In contrast, hmARCs lack the Fd domain and require a human cytochrome b5 (hCyt b5 ) and a human NADH Cyt b5 reductase (hCyt b5- R) to reduce NHC. The ARC proteins in the plant kingdom are uncharacterized. We demonstrate that Chlamydomonas reinhardtii mutants defective in Moco biosynthesis genes are sensitive to the NHC N 6 -hydroxylaminopurine (HAP). The Chlamydomonas reinhardtii ARC protein crARC has been purified and characterized. The six Chlamydomonas Fds were isolated, but none of them are required by crARC to reduce HAP. We have also purified and characterized five C. reinhardtii Cyt b5 (crCyt b5 ) and two flavin reductases, one that is NADPH dependent (crCysJ) and one that is NADH dependent (crCyt b5 -R). The data show that crARC uses crCyt b5 - 1 and crCyt b5 -R to reduce HAP. The crARC has a Zn-dependent activity, and the presence of Zn increases its V max more than 14-fold. In addition, all five cysteines of crARC were substituted by alanine, and we demonstrate that the fully conserved cysteine 252 is essential for both Moco binding and catalysis. Therefore, it is proposed that crARC belongs to the sulfite oxidase family of Moco enzymes.

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Yanase, Takumi, Junko Okuda-Shimazaki, Ryutaro Asano, Kazunori Ikebukuro, Koji Sode, and Wakako Tsugawa. "Development of a Versatile Method to Construct Direct Electron Transfer-Type Enzyme Complexes Employing SpyCatcher/SpyTag System." International Journal of Molecular Sciences 24, no. 3 (January 17, 2023): 1837. http://dx.doi.org/10.3390/ijms24031837.

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The electrochemical enzyme sensors based on direct electron transfer (DET)-type oxidoreductase-based enzymes are ideal for continuous and in vivo monitoring. However, the number and types of DET-type oxidoreductases are limited. The aim of this research is the development of a versatile method to create a DET-type oxidoreductase complex based on the SpyCatcher/SpyTag technique by preparing SpyCatcher-fused heme c and SpyTag-fused non-DET-type oxidoreductases, and by the in vitro formation of DET-type oxidoreductase complexes. A heme c containing an electron transfer protein derived from Rhizobium radiobacter (CYTc) was selected to prepare SpyCatcher-fused heme c. Three non-DET-type oxidoreductases were selected as candidates for the SpyTag-fused enzyme: fungi-derived flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenase (GDH), an engineered FAD-dependent d-amino acid oxidase (DAAOx), and an engineered FMN-dependent l-lactate oxidase (LOx). CYTc-SpyCatcher (CYTc-SC) and SpyTag-Enzymes (ST-GDH, ST-DAAOx, ST-LOx) were prepared as soluble molecules while maintaining their redox properties and catalytic activities, respectively. CYTc-SC/ST-Enzyme complexes were formed by mixing CYTc-SpyCatcher and SpyTag-Enzymes, and the complexes retained their original enzymatic activity. Remarkably, the heme domain served as an electron acceptor from complexed enzymes by intramolecular electron transfer; consequently, all constructed CYTc-SC/ST-Enzyme complexes showed DET ability to the electrode, demonstrating the versatility of this method.

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Buey, Rubén, Ruth Schmitz, Bob Buchanan, and Monica Balsera. "Crystal Structure of the Apo-Form of NADPH-Dependent Thioredoxin Reductase from a Methane-Producing Archaeon." Antioxidants 7, no. 11 (November 17, 2018): 166. http://dx.doi.org/10.3390/antiox7110166.

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The redox regulation of proteins via reversible dithiol/disulfide exchange reactions involves the thioredoxin system, which is composed of a reductant, a thioredoxin reductase (TR), and thioredoxin (Trx). In the pyridine nucleotide-dependent Trx reduction pathway, reducing equivalents, typically from reduced nicotinamide adenine dinucleotide phosphate (NADPH), are transferred from NADPH-TR (NTR) to Trx and, in turn, to target proteins, thus resulting in the reversible modification of the structural and functional properties of the targets. NTR enzymes contain three functional sites: an NADPH binding pocket, a non-covalently bound flavin cofactor, and a redox-active disulfide in the form of CxxC. With the aim of increasing our knowledge of the thioredoxin system in archaea, we here report the high-resolution crystal structure of NTR from the methane-generating organism Methanosarcina mazei strain Gö1 (MmNTR) at 2.6 Å resolution. Based on the crystals presently described, MmNTR assumes an overall fold that is nearly identical to the archetypal fold of authentic NTRs; however, surprisingly, we observed no electron density for flavin adenine dinucleotide (FAD) despite the well-defined and conserved FAD-binding cavity in the folded module. Remarkably, the dimers of the apo-protein within the crystal were different from those observed by small angle X-ray scattering (SAXS) for the holo-protein, suggesting that the binding of the flavin cofactor does not require major protein structural rearrangements. Rather, binding results in the stabilization of essential parts of the structure, such as those involved in dimer stabilization. Altogether, this structure represents the example of an apo-form of an NTR that yields important insight into the effects of the cofactor on protein folding.

Journal articles on the topic 'Flavin hydroquinone dependent Enzymes'

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