Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: KEGG:D02011 (FAD)
5,530 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

AhpF, the flavoprotein reductase component of the Salmonella typhimurium alkyl hydroperoxide reductase system, catalyzes the reduction of an intersubunit disulfide bond in the peroxidatic active site of the system's other component, AhpC, a member of the peroxiredoxin family. Previous studies have shown that AhpF can be dissected into two functional units, a thioredoxin reductase-like C-terminus (containing FAD and a redox-active disulfide, Cys345-Cys348) and an N-terminal domain containing a second redox-active disulfide center (Cys129-Cys132). The role of the N-terminal domain as the direct reductant of AhpC, mediating electron transfer from the C-terminal redox centers of AhpF, has been firmly established by several approaches. Not known, however, was whether the transfer of electrons between the C-terminal and N-terminal disulfide centers occurred as an inter- or intrasubunit process in dimeric AhpF. Two heterodimeric AhpF species were therefore created in which one of the two pathways was completely disrupted while the other was left partially intact in each construct. Only the heterodimer containing one monomer of wild type AhpF and a monomer of mutated (and truncated) AhpF exhibited peroxidase activity with AhpC indicating that electron transfer between domains of AhpF is an intrasubunit process.
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PMID:Activity of one of two engineered heterodimers of AhpF, the NADH:peroxiredoxin oxidoreductase from Salmonella typhimurium, reveals intrasubunit electron transfer between domains. 1130 Jul 70

Mammalian thioredoxin reductase [EC 1.6.4.5], a homodimeric flavoprotein, has a marked similarity to glutathione reductase. The two cysteines in the N-terminal FAD domain (-Cys59-x-x-x-x-Cys64-) and histidine (His472) are conserved between them at corresponding positions, but the mammalian thioredoxin reductase contains a C-terminal extension of selenocysteine (Sec or U) at the penultimate position and a preceding cysteine (-Gly-Cys497-Sec498-Gly). Introduction of mutations into the cloned rat thioredoxin reductase gene revealed that residues Cys59, Cys64, His472, Cys497, and Sec498, as well as the sequence of Cys497 and Sec498 were essential for thioredoxin-reducing activity. To analyze the catalytic mechanism of the mammalian thioredoxin reductase, the wild-type, U498C, U498S, C59S, and C64S were overproduced in a baculovirus/insect cell system and purified. The wild-type thioredoxin reductase produced in this system, designated as WT, was found to lack the Sec residue and to terminate at Cys497. A Sec-containing thioredoxin reductase, which was purified from COS-1 cells transfected with the wild-type cDNA, was designated as SecWT and was used as an authentic enzyme. Among mutant enzymes, only U498C retained a slight thioredoxin-reducing activity at about three orders magnitude lower than SecWT. WT, U498C, and U498S showed some 5,5'-dithiobis(2-nitrobenzoic acid)-reducing activity and transhydrogenase activity, and C59S and C64S had substantially no such activities. These data and spectral analyses of these enzymes suggest that Cys59 and Cys64 at the N-terminus, in conjunction with His472, function as primary acceptors for electrons from NADPH via FAD, and that the electrons are then transferred to Cys497-Sec498 at the C-terminus for the reduction of oxidized thioredoxin in the mammalian thioredoxin reductase.
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PMID:Roles of N-terminal active cysteines and C-terminal cysteine-selenocysteine in the catalytic mechanism of mammalian thioredoxin reductase. 1132 5

We have found that the binding of NADP+ (Kd = 0.86+/-0.11 microM) enhanced the FAD fluorescence of Arabidopsis thaliana NADPH:thioredoxin reductase (TR, EC 1.6.4.5) by 2 times, whereas the binding of 3-aminopyridine adenine dinucleotide phosphate (AADP+) (Kd < 0.1 microM) quenched the fluorescence by 20%. Thioredoxin (TRX) also enhanced the FAD fluorescence by 35%. The Kd of TR-NADP+ and TR-AADP+ complexes did not change in the presence of 45 microM TRX. Our findings imply that the binding of NADP+ and AADP+ at the NADP(H)-binding site of A. thaliana TR, and/or the binding of TRX in the vicinity of the catalytic disulfide increase the content of fluorescent FR conformer (NADP(H)-binding site adjacent to flavin). The different effects of NADP+ and AADP+ on FAD fluorescence intensity may be explained by the superposition of two opposite factors: i) increased content of fluorescent FR conformer upon binding of NADP+ or AADP+; ii) quenching of FAD fluorescence by electron-donating 3-aminopyridinium ring of AADP+.
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PMID:Conformational change of Arabidopsis thaliana thioredoxin reductase after binding of pyridine nucleotide and thioredoxin. 1137 Oct 7

Cytosolic thioredoxin reductase (TR) is an FAD-containing homodimeric selenoenzyme which, together with thioredoxin (Trx) and NADPH, forms a powerful oxidoreductase system. Cytoplasmic glutathione peroxidase (GPX-1) is a selenoprotein with antioxidant activity. The TR/Trx system has been associated with cellular processes including regulation of cell growth, and modification of activity of transcription factors. TR may also act as an antioxidant. We have measured TR activity, TR concentration, and GPX-1 activity in human hepatic cytosols from foetuses and neonates. The concentration of TR was significantly greater (P<0.05) in foetal (43.6, 37.9-50.8 microg/g protein, median, interquartile range) than in neonatal liver (11.6, 8.70-15.0 microg/g). This was also true of TR activity which was 2.1, 1.8-2.5 U/g protein in foetal, and 0.65, 0.44-0.74 U/g protein in neonatal liver (P<0.0005). Similarly, GPX-1 activity was significantly higher (P<0.005) in the foetal (199.7, 144.0-227.9 U/g protein) than in neonatal (77.0, 58.4-110.3 U/g protein) hepatic cytosol. Overall, foetal liver expressed approx. 3-fold higher activities of TR and GPX-1 than neonatal liver.
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PMID:Thioredoxin reductase and cytoplasmic glutathione peroxidase activity in human foetal and neonatal liver. 1141 Mar 32

The antitrypanosomal and antitumour activities of (2,2':6',2"-terpyridine)platinum(II) complexes have been postulated to be due to their ability to inhibit irreversibly the NADPH/FAD redox enzymes trypanothione reductase and human thioredoxin reductase respectively. Here we show that these platinum(II) complexes metallate recombinant human albumin (rHA) at the single free thiol group (Cys-34). Moreover, the (2,2':6',2"-terpyridine)platinum(II) complex can be transferred from rHA to other thiols, such as 2-hydroxyethanethiol or glutathione. Human serum albumin could therefore provide a natural transport mechanism for the selective delivery of these agents to tumor cells by the enhanced permeability and retention (EPR) mechanism.
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PMID:Transfer of 4'-chloro-2,2':6',2"-terpyridine platinum(II) between human serum albumin, glutathione and other thiolate ligands. A possible selective natural transport mechanism for the delivery of platinum(II) drugs to tumour cells. 1171 36

Many eubacterial genomes including those of Salmonella typhimurium, Streptococcus mutans, and Thermus aquaticus encode a dedicated flavoprotein reductase (AhpF, Nox1, or PrxR) just downstream of the structural gene for their peroxiredoxin (Prx, AhpC) homologue to reduce the latter protein during turnover. In contrast, the obligate anaerobe Clostridium pasteurianum codes for a two-component reducing system upstream of the ahpC homologue. These three structural genes, herein designated cp34, cp9, and cp20, were previously identified upstream of the rubredoxin gene in C. pasteurianum, but were not linked to expression of the latter gene [Mathieu, I., and Meyer, J. (1993) FEMS Microbiol. Lett. 112, 223-227]. cp34, cp9, and cp20 have been expressed in Escherichia coli, and their products have been purified and characterized. Cp34 and Cp9 together catalyze the NADH-dependent reduction of Cp20 to effect the reduction of various hydroperoxide substrates. Cp34, containing noncovalently bound FAD and a redox-active disulfide center, is an unusual member of the low-M(r) thioredoxin reductase (TrxR) family. Like Escherichia coli TrxR, Cp34 lacks the 200-residue N-terminal AhpC-reducing domain present in S. typhimurium AhpF. Although Cp34 is more similar to TrxR than to AhpF in sequence comparisons of the nucleotide-binding domains, experiments demonstrated that NADH was the preferred reductant (Km = 2.65 microM). Cp9 (a distant relative of bacterial glutaredoxins) is a direct electron acceptor for Cp34, possesses a redox-active CXXC active site, and mediates the transfer of electrons from Cp34 to several disulfide-containing substrates including 5,5'-dithiobis(2-nitrobenzoic acid), insulin, and Cp20. These three proteins are proposed to play a vital role in the defense of C. pasteurianum against oxidative damage and may help compensate for the putative lack of catalase activity in this organism.
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PMID:An NADH-dependent bacterial thioredoxin reductase-like protein in conjunction with a glutaredoxin homologue form a unique peroxiredoxin (AhpC) reducing system in Clostridium pasteurianum. 1182 46

The interferon (IFN)-beta and all-trans-retinoic acid combination suppresses tumor growth by inducing apoptosis in several tumor cell lines. A genetic technique permitted the isolation of human thioredoxin reductase (TR) as a critical regulator of IFN/all-trans-retinoic acid-induced cell death. Our recent studies have shown that TR1:thioredoxin 1-regulated cell death is effected in part through the activation of p53-dependent responses. To understand its death regulatory function, we have performed a mutational analysis of TR. Human TR1 has three major structural domains, the FAD binding domain, the NADPH binding domain, and an interface domain (ID). Here, we show that the deletion of the C-terminal interface domain results in a constitutive activation of TR-dependent death responses and promotes p53-dependent gene expression. TR mutant without the ID still retains its dependence on thioredoxin for promoting these responses. Thus, our data suggest that TR-ID acts as a regulatory domain.
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PMID:Mutational analysis of human thioredoxin reductase 1. Effects on p53-mediated gene expression and interferon and retinoic acid-induced cell death. 1195 36

Thioredoxins h are ubiquitous proteins reduced by NADPH- thioredoxin reductase (NTR). They are able to reduce disulphides in target proteins. In monocots, thioredoxins h accumulate at high level in seeds and show a predominant localization in the nucleus of seed cells. These results suggest that the NTR-thioredoxin h system probably plays an important role in seed physiology. To date, the study of this system in monocots is limited by the lack of information about NTR. In the present study, we describe the cloning of a full-length cDNA encoding NTR from wheat ( Triticum aestivum ). The polypeptide deduced from this cDNA shows close similarity to NTRs from Arabidopsis, contains FAD- and NADPH-binding domains and a disulphide probably interacting with the disulphide at the active site of thioredoxin h. Wheat NTR was expressed in Escherichia coli as a His-tagged protein. The absorption spectrum of the purified recombinant protein is typical of flavoenzymes. Furthermore, it showed NADPH-dependent thioredoxin h reduction activity, thus confirming that the cDNA clone reported in the present study encodes wheat NTR. Using the His-tagged NTR and TRXhA (wheat thioredoxin h ), we successfully reconstituted the wheat NTR-thioredoxin h system in vitro, as shown by the insulin reduction assay. A polyclonal antibody was raised against wheat NTR after immunization of rabbits with the purified His-tagged protein. This antibody efficiently detected a single polypeptide of the corresponding molecular mass in seed extracts and it allowed the analysis of the pattern of accumulation of NTR in different wheat organs and developmental stages. NTR shows a wide distribution in wheat, but, surprisingly, its accumulation in seeds is low, in contrast with the level of thioredoxins h.
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PMID:Cloning of thioredoxin h reductase and characterization of the thioredoxin reductase-thioredoxin h system from wheat. 1210 17

The NADPH:2-ketopropyl-coenzyme M oxidoreductase/carboxylase (2-KPCC) is the terminal enzyme in a metabolic pathway that results in the conversion of propylene to the central metabolite acetoacetate in Xanthobacter autotrophicus Py2. This enzyme is an FAD-containing enzyme that is a member of the NADPH:disulfide oxidoreductase (DSOR) family of enzymes that include glutathione reductase, dihydrolipoamide dehydrogenase, trypanothione reductase, thioredoxin reductase, and mercuric reductase. In contrast to the prototypical reactions catalyzed by members of the DSOR family, the NADPH:2-ketopropyl-coenzyme M oxidoreductase/carboxylase catalyzes the reductive cleavage of the thioether linkage of 2-ketopropyl-coenzyme M, and the subsequent carboxylation of the ketopropyl cleavage product, yielding the products acetoacetate and free coenzyme M. The structure of 2-KPCC reveals a unique active site in comparison to those of other members of the DSOR family of enzymes and demonstrates how the enzyme architecture has been adapted for the more sophisticated biochemical reaction. In addition, comparison of the structures in the native state and in the presence of bound substrate indicates the binding of the substrate 2-ketopropyl-coenzyme M induces a conformational change resulting in the collapse of the substrate access channel. The encapsulation of the substrate in this manner is reminiscent of the conformational changes observed in the well-characterized CO2-fixing enzyme ribulose 1,5-bisphosphate carboxylase/oxidase (Rubisco).
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PMID:Structural basis for CO2 fixation by a novel member of the disulfide oxidoreductase family of enzymes, 2-ketopropyl-coenzyme M oxidoreductase/carboxylase. 1239 15

We have identified and characterized a thermostable thioredoxin system in the aerobic hyperthermophilic archaeon Aeropyrum pernix K1. The gene (Accession no. APE0641) of A. pernix encoding a 37 kDa protein contains a redox active site motif (CPHC) but its N-terminal extension region (about 200 residues) shows no homology within the genome database. A second gene (Accession no. APE1061) has high homology to thioredoxin reductase and encodes a 37 kDa protein with the active site motif (CSVC), and binding sites for FAD and NADPH. We cloned the two genes and expressed both proteins in E. coli. It was observed that the recombinant proteins could act as an NADPH-dependent protein disulfide reductase system in the insulin reduction. In addition, the APE0641 protein and thioredoxin reductase from E. coli could also catalyze the disulfide reduction. These indicated that APE1061 and APE0641 express thioredoxin (ApTrx) and thioredoxin reductase (ApTR) of A. pernix, respectively. ApTR is expressed as an active homodimeric flavoprotein in the E. coli system. The optimum temperature was above 90 degrees C, and the half-life of heat inactivation was about 4 min at 110 degrees C. The heat stability of ApTR was enhanced in the presence of excess FAD. ApTR could reduce both thioredoxins from A. pernix and E. coli and showed a similar molar specific activity for both proteins. The standard state redox potential of ApTrx was about -262 mV, which was slightly higher than that of Trx from E. coli (-270 mV). These results indicate that a lower redox potential of thioredoxin is not necessary for keeping catalytic disulfide bonds reduced and thereby coping with oxidative stress in an aerobic hyperthermophilic archaea. Furthermore, the thioredoxin system of aerobic hyperthermophilic archaea is biochemically close to that of the bacteria.
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PMID:Identification and characterization of thioredoxin and thioredoxin reductase from Aeropyrum pernix K1. 1242 40


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