Reduction of Fe(III) Ions Complexed to Physiological Ligands by Lipoyl Dehydrogenase and Other Flavoenzymes in Vitro

Petrat, Frank; Paluch, Sandra; Dogruöz, Elke; Dörfler, P; Kirsch, Michael; Korth, Hans‐Gert; Sustmann, Reiner; Groot, Herbert de

doi:10.1074/jbc.m305291200

Cited by 69 publications

(62 citation statements)

References 77 publications

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“…In contrast, hydroquinone and N-acetyl-L-cysteine showed little or no effect. Nevertheless, different reducing agents are known to show variable efficiencies for Fe 3+ reduction (30). As such, we preincubated the reaction mixture containing Fe 3+ ions for 30 min in the presence of a reducing agent and subsequently started the reactions by the addition of TET1-CD.…”

Section: Resultsmentioning

confidence: 99%

Retinol and ascorbate drive erasure of epigenetic memory and enhance reprogramming to naïve pluripotency by complementary mechanisms

Hore

Meyenn

Ravichandran

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

151

139

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Epigenetic memory, in particular DNA methylation, is established during development in differentiating cells and must be erased to create naïve (induced) pluripotent stem cells. The ten-eleven translocation (TET) enzymes can catalyze the oxidation of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) and further oxidized derivatives, thereby actively removing this memory. Nevertheless, the mechanism by which the TET enzymes are regulated, and the extent to which they can be manipulated, are poorly understood. Here we report that retinoic acid (RA) or retinol (vitamin A) and ascorbate (vitamin C) act as modulators of TET levels and activity. RA or retinol enhances 5hmC production in naïve embryonic stem cells by activation of TET2 and TET3 transcription, whereas ascorbate potentiates TET activity and 5hmC production through enhanced Fe 2+ recycling, and not as a cofactor as reported previously. We find that both ascorbate and RA or retinol promote the derivation of induced pluripotent stem cells synergistically and enhance the erasure of epigenetic memory. This mechanistic insight has significance for the development of cell treatments for regenenerative medicine, and enhances our understanding of how intrinsic and extrinsic signals shape the epigenome.

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Section: Resultsmentioning

confidence: 99%

Retinol and ascorbate drive erasure of epigenetic memory and enhance reprogramming to naïve pluripotency by complementary mechanisms

Hore

Meyenn

Ravichandran

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

151

139

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“…The purification and characterization of SfrAB as an Fe(III) reductase took place before a genetic system for analysing gene function in G. sulfurreducens was readily available. In the search for Fe(III) reductases, the genetic approach may be superior to a strictly biochemical approach because many enzymes, particularly those with flavin cofactors or flavin-reductase acitivity, may non-specifically reduce Fe(III) in vitro (Filisetti et al, 2005;Fischer et al, 2002;Petrat et al, 2003;Schroder et al, 2003). In light of these results, previous studies describing the purification of membrane-bound complexes that had NADH-dependent Fe(III) reductase activity and contained both cytochromes and flavin cofactors (Gaspard et al, 1998;Magnuson et al, 2000) should be interpreted with caution.…”

Section: Discussionmentioning

confidence: 99%

Involvement of Geobacter sulfurreducens SfrAB in acetate metabolism rather than intracellular, respiration-linked Fe(III) citrate reduction

et al. 2007

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A soluble ferric reductase, SfrAB, which catalysed the NADPH-dependent reduction of chelated Fe(III), was previously purified from the dissimilatory Fe(III)-reducing micro-organism Geobacter sulfurreducens, suggesting that reduction of chelated forms of Fe(III) might be cytoplasmic. However, metabolically active spheroplast suspensions could not catalyse acetate-dependent Fe(III) citrate reduction, indicating that periplasmic and/or outer-membrane components were required for Fe(III) citrate reduction. Furthermore, phenotypic analysis of an SfrAB knockout mutant suggested that SfrAB was involved in acetate metabolism rather than respiration-linked Fe(III) reduction. The mutant could not grow via the reduction of either Fe(III) citrate or fumarate when acetate was the electron donor but could grow with either acceptor if either hydrogen or formate served as the electron donor. Following prolonged incubation in acetate : fumarate medium in the absence of hydrogen and formate, an 'acetate-adapted' SfrAB-null strain was isolated that was capable of growth on acetate : fumarate medium but not acetate : Fe(III) citrate medium. Comparison of gene expression in this strain with that of the wild-type revealed upregulation of a potential NADPH-dependent ferredoxin oxidoreductase as well as genes involved in energy generation and amino acid uptake, suggesting that NADPH homeostasis and the tricarboxylic acid (TCA) cycle were perturbed in the 'acetate-adapted' SfrAB-null strain. Membrane and soluble fractions prepared from the 'acetate-adapted' strain were depleted of NADPH-dependent Fe(III), viologen and quinone reductase activities. These results indicate that cytoplasmic, respiration-linked reduction of Fe(III) by SfrAB in vivo is unlikely and suggest that deleting SfrAB may interfere with growth via acetate oxidation by interfering with NADP regeneration.

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“…In addition, DLD has diaphorase activity, being able to catalyze the oxidation of NADH to NAD ϩ by using different electron acceptors such as O 2 , labile ferric iron (3), nitric oxide (4), and ubiquinone (5,6). In this capacity, DLD is believed to primarily have a prooxidant role, achieved by reducing O 2 to a superoxide radical or ferric to ferrous iron, which in turn catalyzes production of hydroxyl radical through Fenton chemistry (3). However, the ability to scavenge nitric oxide and to reduce ubiquinone to ubiquinol suggests that the diaphorase activity of DLD may also have an antioxidant role (4-6).…”

mentioning

confidence: 99%

Cryptic proteolytic activity of dihydrolipoamide dehydrogenase

Babady¹,

Pang

Elpeleg

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

111

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The mitochondrial enzyme, dihydrolipoamide dehydrogenase (DLD), is essential for energy metabolism across eukaryotes. Here, conditions known to destabilize the DLD homodimer enabled the mouse, pig, or human enzyme to function as a protease. A catalytic dyad (S456 -E431) buried at the homodimer interface was identified. Serine protease inhibitors and an S456A or an E431A point mutation abolished the proteolytic activity, whereas other point mutations at the homodimer interface domain enhanced the proteolytic activity, causing partial or complete loss of DLD activity. In humans, mutations in the DLD homodimer interface have been linked to an atypical form of DLD deficiency. These findings reveal a previously unrecognized mechanism by which certain DLD mutations can simultaneously induce the loss of a primary metabolic activity and the gain of a moonlighting proteolytic activity. The latter could contribute to the metabolic derangement associated with DLD deficiency and represent a target for therapies of this condition.is a f lavindependent oxidoreductase required for the complete reaction of at least five different multienzyme complexes. In the mitochondrial matrix, the DLD homodimer functions as the E3 component of the pyruvate, ␣-ketoglutarate, and branchedchain amino acid-dehydrogenase complexes and the glycine cleavage system. In the context of these four multienzyme complexes, DLD utilizes dihydrolipoic acid and NAD ϩ to generate lipoic acid and NADH (1). The opposite reaction, from lipoic acid and NADH to dihydrolipoic acid and NAD ϩ , is catalyzed by the DLD homodimer in the context of the NAD ϩ -dependent peroxidase-peroxinitrate reductase of Mycobacterium tuberculosis (2). In addition, DLD has diaphorase activity, being able to catalyze the oxidation of NADH to NAD ϩ by using different electron acceptors such as O 2 , labile ferric iron (3), nitric oxide (4), and ubiquinone (5, 6). In this capacity, DLD is believed to primarily have a prooxidant role, achieved by reducing O 2 to a superoxide radical or ferric to ferrous iron, which in turn catalyzes production of hydroxyl radical through Fenton chemistry (3). However, the ability to scavenge nitric oxide and to reduce ubiquinone to ubiquinol suggests that the diaphorase activity of DLD may also have an antioxidant role (4-6). The oligomeric state of DLD can change from dimeric to monomeric or tetrameric depending on the pH in the mitochondrial matrix, and changes in the oligomeric state of the protein have been shown to correlate with a shift from DDL activity (only present in dimeric and tetrameric DLD) to diaphorase activity (present in both oligomeric and monomeric forms of the protein) (7,8). Thus, DLD represents a highly versatile oxidoreductase with multiple critical roles in energy metabolism and redox balance (2,7,(9)(10)(11)(12).Here, we found that DLD can also function as a moonlighting protease. Moonlighting enzymes are a growing category of molecules that can accomplish multiple functions through a variety of mechanisms including, among other...

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Reduction of Fe(III) Ions Complexed to Physiological Ligands by Lipoyl Dehydrogenase and Other Flavoenzymes in Vitro

Cited by 69 publications

References 77 publications

Retinol and ascorbate drive erasure of epigenetic memory and enhance reprogramming to naïve pluripotency by complementary mechanisms

Retinol and ascorbate drive erasure of epigenetic memory and enhance reprogramming to naïve pluripotency by complementary mechanisms

Involvement of Geobacter sulfurreducens SfrAB in acetate metabolism rather than intracellular, respiration-linked Fe(III) citrate reduction

Cryptic proteolytic activity of dihydrolipoamide dehydrogenase

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