Induced internal redox processes in molybdenum-sulfur chemistry: conversion of tetrathiomolybdate(2-) ion to octathiodimolybdate(2-) ion by organic disulfides

Pan, W.-H.; Harmer, Mark A.; Halbert, Thomas R.; Stiefel, Edward I.

doi:10.1021/ja00314a054

Cited by 99 publications

(45 citation statements)

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“…Inspection of the dihydro pyranopterin structure reveals an additional mechanism by which modulation of the Mo/W reduction potentials can occur. Protonation of N-5 can facilitate an internal redox reaction between the piperazine ring and the dithiolene (27,28), leading to the formation of a monoanionic thiol-thione type chelate (Fig. 5B).…”

Section: Resultsmentioning

confidence: 99%

Pyranopterin conformation defines the function of molybdenum and tungsten enzymes

Rothery

Stein

Solomonson

et al. 2012

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

119

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We have analyzed the conformations of 319 pyranopterins in 102 protein structures of mononuclear molybdenum and tungsten enzymes. These span a continuum between geometries anticipated for quinonoid dihydro, tetrahydro, and dihydro oxidation states. We demonstrate that pyranopterin conformation is correlated with the protein folds defining the three major mononuclear molybdenum and tungsten enzyme families, and that binding-site microtuning controls pyranopterin oxidation state. Enzymes belonging to the bacterial dimethyl sulfoxide reductase (DMSOR) family contain a metal-bis-pyranopterin cofactor, the two pyranopterins of which have distinct conformations, with one similar to the predicted tetrahydro form, and the other similar to the predicted dihydro form. Enzymes containing a single pyranopterin belong to either the xanthine dehydrogenase (XDH) or sulfite oxidase (SUOX) families, and these have pyranopterin conformations similar to those predicted for tetrahydro and dihydro forms, respectively. This work provides keen insight into the roles of pyranopterin conformation and oxidation state in catalysis, redox potential modulation of the metal site, and catalytic function.energetics | molybdoenzymes | redox chemistry T he pyranopterin dithiolene ligand is present in all molybdenum (Mo) and tungsten (W) containing enzymes with the exception of nitrogenase (1). These enzymes, known as mononuclear Mo/W enzymes, play pivotal roles in metabolism, global geochemical cycles, and microbial metabolic diversity (2-5). Their active sites, comprising a Mo or W ion and one or two pyranopterins, catalyze a diversity of redox transformations spanning a reduction potential range of approximately one volt. While the immediate environment of the substrate-binding metal ion is critically important in catalysis (6), little attention has been focused on the impact of variations in pyranopterin structure on enzyme function.Protein-bound pyranopterins are typically interpreted as having the tricyclic structure depicted in Fig. 1A, comprising pyrimidine, piperazine, and pyran-dithiolene rings. The dithiolene chelate binds a single Mo/W atom, which constitutes the catalytic active site. The pyranopterin shown in Fig. 1A is also known as the tetrahydro mononucleotide form due to the oxidation state of its piperazine ring and the presence of a phosphomethyl group attached to its C-2 atom (1). This form is assigned to the xanthine dehydrogenases, and in its cytosine dinucleotide form to the bacterial carbon monoxide dehydrogenases and aldehyde dehydrogenases (these enzymes are referred to collectively as the XDH family). It is also assigned to the sulfite oxidases and plant nitrate reductases [SUOX family (1, 5)].Mononuclear Mo/W enzymes also coordinate metal-bis-pyranopterin cofactors, either as the metal-bis(pyranopterin guanine dinucleotide) form (Fig. 1D) found in the dimethyl sulfoxide reductase family of molybdoenzyme subunits (DMSOR family), or the mononuclear bis-pyranopterin form found in the thermophilic aldehyde oxidoreductases...

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Section: Resultsmentioning

confidence: 99%

Pyranopterin conformation defines the function of molybdenum and tungsten enzymes

Rothery

Stein

Solomonson

et al. 2012

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

119

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“…(4); R = Ph, p-C 6 H 4 NO 2 ) is another early example of induced internal electron transfer from Stiefel's laboratory [77]. Here, the disulfide acts as an oxidant but induces the internal reduction of Mo(VI) to Mo(V) and formation of (NH 4 ) 2 [Mo 2 S 2 (l-S) 2 (S 2 ) 2 ] (isolated as the PPh þ 4 salt).…”

Section: Group 6 Chemistrymentioning

confidence: 99%

“…The dinuclear compound, containing the dianion shown in Fig. 12, is also formed when (NH 4 ) 2 [MoS 4 ] reacts with PhSeSePh [77]. (l-S) 2 (S 2 ) 2 ] 2À (k max = 572 nm).…”

Section: Group 6 Chemistrymentioning

confidence: 99%

“…These reactions are often characterized by the dismemberment of the dithio acid ligand and the combination of its parts with the incoming alkyne; we have coined the term ''melded ligand'' to describe ligands produced in reactions of this type. The first examples, orange (77) and green (78), were produced in the reactions of [Mo 2 (l-S 2 ) 2 -(S 2 CNR 2 ) 4 ]X 2 , MoO(S 2 )(S 2 CNR 2 ) 2 or Mo(S 2 )(S 2 CNR 2 ) 3 (R = Me, Et) with excess DMAC in refluxing chlorinated solvents [105,141]. Complexes (77) were slowly converted to (78) in hot inert solvents or more quickly upon melting; the structures of two derivatives are displayed in Fig.…”

Section: Ligand Melding Reactionsmentioning

confidence: 99%

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Facets of early transition metal–sulfur chemistry: Metal–sulfur ligand redox, induced internal electron transfer, and the reactions of metal–sulfur complexes with alkynes

Young

2007

Journal of Inorganic Biochemistry

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“…These reactions which are often complicated by redox processes concerning metal centres and/or ancillary ligands have been extended to various organic substrates [6][7][8][9]. The rationalization of the behaviour of tetraoxothiometalates is not trivial.…”

Section: Introductionmentioning

confidence: 99%

Reactivity of tetrathiometalates with alkynes. Synthesis and characterisation of dithiolene complexes of Mo, W, and V by ESMS and XRD

Mallard

Simonnet‐Jégat²,

Lavanant³

et al. 2007

Transition Met Chem

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4 ] 5 were isolated in the solid state. The structures of 2a, 3, 4 and 5 were determined by single crystal X-ray diffraction study. The compounds 1 and 2b were characterised in solution by ESMS (Electrospray Mass Spectrometry) and in the solid state by IR spectroscopy. ESMS data also allowed proposal of a reaction scheme which rationalizes the formation of the different species present in solution.

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Induced internal redox processes in molybdenum-sulfur chemistry: conversion of tetrathiomolybdate(2-) ion to octathiodimolybdate(2-) ion by organic disulfides

Cited by 99 publications

References 3 publications

Pyranopterin conformation defines the function of molybdenum and tungsten enzymes

Pyranopterin conformation defines the function of molybdenum and tungsten enzymes

Facets of early transition metal–sulfur chemistry: Metal–sulfur ligand redox, induced internal electron transfer, and the reactions of metal–sulfur complexes with alkynes

Reactivity of tetrathiometalates with alkynes. Synthesis and characterisation of dithiolene complexes of Mo, W, and V by ESMS and XRD

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