Oxidation of nickel thiolate ligands by dioxygen

Mirza, Shaukat A.; Pressler, Michelle A.; Kumar, Manoj; Day, Roberta O.; Maroney, Michael J.

doi:10.1021/ic00058a038

Cited by 86 publications

(123 citation statements)

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“…The resulting structures showed little effect by addition of the proton, and in fact produced shorter Ni-S bond lengths. This is consistent with model studies that involve protonation [84], alkylation [56,[85][86][87], and oxidation [36,37,53,55,[88][89][90][91] of sulfur in nickel thiolate complexes and reveal that little structural change accompanies the chemical modifi cations. The computational results correlate well with the known model complexes and support the model for coordinated thiols in reduced NiSOD.…”

Section: Model Studiessupporting

confidence: 88%

“…In contrast, the nickel active site in NiSOD incorporates cysteine thiolate S-donors, three different types of nitrogen donors, and lacks an aqua/hydroxo ligand. The strategy of using cysteine-thiolate ligands to access the higher oxidation state (in this case the Ni(III/II) couple), is a very common one in other nickel-redox enzymes [35], but is unprecedented in SODs, and unexpected because of the facile oxidation of thiolates, including metal thiolate ligands, with H 2 O 2 and O 2 [36,37].…”

Section: Superoxide Dismutase Enzymesmentioning

confidence: 99%

“…In addition to disulfi de formation, oxidations of nickel thiolates by H 2 O 2 and O 2 (the products of the SOD reaction) are known to form a variety of S-oxygenates, including sulfenate, sulfi nate and sulfonate complexes [36,37,[53][54][55]. Based on synthetic model studies, the expected consequence of such oxidations in the enzyme would be to increase the redox potential of the Ni site to values that are no longer appropriate for SOD catalysis [53,[56][57][58].…”

Section: Nickel Redox Chemistrymentioning

confidence: 99%

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Nickel Superoxide Dismutase

Bryngelson

Maroney

2007

Nickel and Its Surprising Impact in Nature

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Section: Model Studiessupporting

confidence: 88%

Section: Superoxide Dismutase Enzymesmentioning

confidence: 99%

Section: Nickel Redox Chemistrymentioning

confidence: 99%

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Nickel Superoxide Dismutase

Bryngelson

Maroney

2007

Nickel and Its Surprising Impact in Nature

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“…The position of sulfur in the substrate complex also may allow the His-155-Tyr-157-Cys-93 triad to stabilize cationic intermediates generated during catalysis. Alternatively, nickel thiolate complexes were hypothesized to be oxidized by nucleophilic attack of the coordinated thiol on O 2 , leading to a thiadioxirane intermediate (32). However, related work with iron-thiolate complexes did not support formation of the thiadioxirane intermediate (33).…”

Section: Discussionmentioning

confidence: 99%

Structure and mechanism of mouse cysteine dioxygenase

McCoy

Bailey

Bitto

et al. 2006

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

191

238

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Cysteine dioxygenase (CDO) catalyzes the oxidation of L-cysteine to cysteine sulfinic acid. Deficiencies in this enzyme have been linked to autoimmune diseases and neurological disorders. The x-ray crystal structure of CDO from Mus musculus was solved to a nominal resolution of 1.75 Å. The sequence is 91% identical to that of a human homolog. The structure reveals that CDO adopts the typical ␤-barrel fold of the cupin superfamily. The NE2 atoms of His-86, -88, and -140 provide the metal binding site. The structure further revealed a covalent linkage between the side chains of Cys-93 and Tyr-157, the cysteine of which is conserved only in eukaryotic proteins. Metal analysis showed that the recombinant enzyme contained a mixture of iron, nickel, and zinc, with increased iron content associated with increased catalytic activity. Details of the predicted active site are used to present and discuss a plausible mechanism of action for the enzyme.cupin ͉ cysteine metabolism ͉ O2-activation M ouse cysteine dioxygenase (CDO) catalyzes the initial step in the biochemical pathway used for oxidation of cysteine to sulfate (1), namely the oxidation of L-cysteine to cysteine sulfinic acid as shown in Fig. 1. The enzyme activity has important medical implications because elevated cysteine levels have been associated with Parkinson's and Alzheimer's diseases (2). High cysteine-to-sulfate ratios have been observed in patients suffering from systemic lupus erthematosus and rheumatoid arthritis (3, 4). Moreover, the Hallervorden-Spatz syndrome, a neurological disorder associated with iron accumulation, has been linked to a decline in CDO activity (5).CDO displays significant sequence identity with some members of the cupin superfamily (6), which have a conserved ␤-barrel fold and share two conserved sequence motifs: G(X) 5 HXH(X) 3,4 E(X) 6 G and G(X) 5 PXG(X) 2 H(X) 3 N (6-8).The two His and Glu residues from the first motif and the His from the second motif coordinate the metal ion in germin, the superfamily archetype (9). The Mus musculus CDO sequence contains the first motif with the exception of the glutamate, which is replaced by cysteine. This substitution is conserved in other eukaryotic CDOs. The second motif is less conserved, and only the His and Asn residues are present in the mouse CDO.CDO does not require an external reductant ( Fig. 1) and incorporates both oxygen atoms from O 2 (10), which justifies the dioxygenase classification, but relatively little else is known about the reaction mechanism. The recombinant enzyme from Rattus norvegicus has been purified and characterized by steadystate kinetics (11); the mouse enzyme investigated here has an identical sequence. Reconstitution of the rat apoenzyme with various transition metals confirmed that iron was required for activity, in accord with the earlier conclusions (1). Moreover, the recombinant rat enzyme was active without a second interacting factor, despite previous reports suggesting that additional components were required (12, 13).Here, we describe the x-ra...

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“…More recently, Maroney and coworkers reported monosulfonate formation occurs when (N,N 0 -dimethyl-N,N 0 -bis(2-mecaptoethyl)-1,3-propane diaminato)nickel(II) (b, Scheme 3) subjected to oxidants [60]. The slow O 2 reaction with a monosulfinate precursor (initially formed) to the product sulfonate complex was proposed to occur as a monoxygenase type oxygen atom transfer reaction, rather than as a dioxygenase-like reaction, as previously described for sulfinate formation using O 2 from a thiolate complex [61][62][63][64]. Prior to this work, Maroney's many studies on oxidation of nickel thiolate compounds only resulted in sulfinate and sulfenate (and not sulfonate) products [64][65][66].…”

Section: Low-temperature Reactions Of Copper(i) Complexes With O 2 Anmentioning

confidence: 88%