Redox chemistry of cobalamin and its derivatives

Dereven’kov, Ilia А.; Salnikov, Denis S.; Silaghi-Dumitrescu, Radu; Макаров, С. В.; Койфман, О. И.

doi:10.1016/j.ccr.2015.11.001

Cited by 94 publications

(63 citation statements)

References 202 publications

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“…The complex can exist in three oxidations states of cobalt: Co(III), Co(II) and Co(I). This fact and the large number of possible ligands which can bind in the β‐position give the cobalamins a varied and rich coordination and redox chemistry which has recently been reviewed . Important β ligands are cyanide (CN ‐ ) in cyanocobalamin (CNCbl(III)), water (H 2 O) in aquocobalamin (H 2 OCbl(III), alkyl groups such as (CH 3 ‐) in methylcobalamin (MeCbl(III)) and 5′‐deoxyadenosyl‐ in adenosylcobalamin (AdoCbl(III)) which are cofactors for B12‐dependent human enzymes, and glutathionylcobalamin (GSCbl(III)) which is the subject of this report.…”

Section: Introductionsupporting

confidence: 79%

The Reductive Cleavage Mechanism and Complex Stability of Glutathionyl‐Cobalamin in Acidic Media

Sajan

Birke

2016

Electroanalysis

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The mechanisms of the electrode reduction of vitamin B12a and the reductive cleavage of glutathionyl cobalamin (GSCbl) were investigated with digital simulations in acid media at pH 3.78 and 2.78. Even though the pH is quite acidic, the 1‐electron reduction of B12a goes through the base‐on form in a step‐wise sequence forming base‐on vitamin B12r which then is protonated to the base‐off form, and finally reduced in another 1‐electron step to vitamin B12s Unlike the case of B12a, the GSCbl is found to go by a 1‐electron overall mechanism. In this case, electronic structure calculations at the B3LYP/6‐311G(d,p) level for a model GSCbl complex show that the one‐electron adduct is a radical anion with the unpaired electron in a corrin ring π* orbital. When the axial 5,6‐dimethylbenzimidazole dissociates, the Co(III)‐S bond will break forming Vitamin B12s and the GS• radical. This reductive cleavage mechanism is the same as in the case of alkylcobalmins and is relevant to the biological mechanism of the B12 trafficking chaperone proteins, CblC, for processing GSCbl in B12 dependent enzyme reactions. Finally, we determined conditional stability constants for the formation of the GSCbl complex, Kobs, which are 4.4±0.5×103 M−1 and 9.9±0.1×102 M−1 at pH 3.78 and 2.78, respectively.

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Section: Introductionsupporting

confidence: 79%

The Reductive Cleavage Mechanism and Complex Stability of Glutathionyl‐Cobalamin in Acidic Media

Sajan

Birke

2016

Electroanalysis

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“…A more plausible source of NO 2 -cobalamin in AOA is the rapid reaction between reduced cobalamin and intracellular NO (Sharma et al, 2003;Dereven'kov et al, 2016). Gaseous NO is an intermediate of ammonia oxidation in both AOA and anammox bacteria (Kartal et al, 2011;Martens-Habbena et al, 2015;Kozlowski et al, 2016) and may diffuse into the cell to react with the reduced cobalamin that forms during cellular processing, forming nitrosylcobalamin (NO-cobalamin).…”

Section: Resultsmentioning

confidence: 99%

Accumulation of NO₂‐cobalamin in nutrient‐stressed ammonia‐oxidizing archaea and in the oxygen deficient zone of the eastern tropical North Pacific

Qin

Amin

Devol

et al. 2018

Environ Microbiol Rep

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Cobalamin (vitamin B ) is a precious resource in natural systems that is produced by select prokaryotes and required by a broad range of organisms. In this way, the production of cobalamin reinforces numerous microbial interdependencies. Here we report the accumulation of an unusual form of cobalamin, nitrocobalamin (NO -cobalamin), in a marine oxygen deficient zone (ODZ), isolates of ammonia-oxidizing archaea (AOA), and an anaerobic ammonium-oxidizing (anammox) bacteria enriched bioreactor. Low oxygen waters were enriched in NO -cobalamin, and AOA isolates experiencing ammonia or copper stress produced more NO -cobalamin, though there is wide strain-to-strain and batch-to-batch variability. NO -cobalamin has no known biochemical role. We hypothesize that AOA and anammox bacteria are a source of marine NO -cobalamin in the environment via a reactive nitrogen intermediate. These findings suggest connections between cobalamin forms and nitrogen transformations, physiological stress and ocean deoxygenation.

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“…Eu(II)–DTPA was identified as suitable electron donor for titration experiments of low‐potential redox centers. It extends the small number of reductants known to be applicable for the generation of [Co I ] corrinoids . By the application of Eu(II)–DTPA, we identified the redox potential differences, which occur during the reduction of protein‐bound corrinoid cofactors involved in O ‐demethylation.…”

Section: Discussionmentioning

confidence: 99%

“…It extends the small number of reductants known to be applicable for the generation of [Co I ] corrinoids. 31 By the application of Eu(II)-DTPA, we identified the redox potential differences, which occur during the reduction of protein-bound corrinoid cofactors involved in O-demethylation. In contrast to other thermodynamically unfavorable electron transfer processes, in which the potential of the electron is lowered to allow its transfer to the active site, 9 in O-demethylases the potential of the electronaccepting site is increased to enable a spontaneous flow of electrons ( Figure 2).…”

Section: Discussionmentioning

confidence: 99%

Redox potential changes during ATP‐dependent corrinoid reduction determined by redox titrations with europium(II)–DTPA

2019

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Corrinoids are essential cofactors of enzymes involved in the C1 metabolism of anaerobes. The active, super‐reduced [CoI] state of the corrinoid cofactor is highly sensitive to autoxidation. In O‐demethylases, the oxidation to inactive [CoII] is reversed by an ATP‐dependent electron transfer catalyzed by the activating enzyme (AE). The redox potential changes of the corrinoid cofactor, which occur during this reaction, were studied by potentiometric titration coupled to UV/visible spectroscopy. By applying europium(II)–diethylenetriaminepentaacetic acid (DTPA) as a reductant, we were able to determine the midpoint potential of the [CoII]/[CoI] couple of the protein‐bound corrinoid cofactor in the absence and presence of AE and/or ATP. The data revealed that the transfer of electrons from a physiological donor to the corrinoid as the electron‐accepting site is achieved by increasing the potential of the corrinoid cofactor from −530 ± 15 mV to −250 ± 10 mV (ESHE, pH 7.5). The first 50 to 100 mV of the shift of the redox potential seem to be caused by the interaction of nucleotide‐bound AE with the corrinoid protein or its cofactor. The remaining 150–200 mV had to be overcome by the chemical energy of ATP hydrolysis. The experiments revealed that Eu(II)–DTPA, which was already known as a powerful reducing agent, is a suitable electron donor for titration experiments of low‐potential redox centers. Furthermore, the results of this study will contribute to the understanding of thermodynamically unfavorable electron transfer processes driven by the power of ATP hydrolysis.

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Redox chemistry of cobalamin and its derivatives

Cited by 94 publications

References 202 publications

The Reductive Cleavage Mechanism and Complex Stability of Glutathionyl‐Cobalamin in Acidic Media

The Reductive Cleavage Mechanism and Complex Stability of Glutathionyl‐Cobalamin in Acidic Media

Accumulation of NO₂‐cobalamin in nutrient‐stressed ammonia‐oxidizing archaea and in the oxygen deficient zone of the eastern tropical North Pacific

Redox potential changes during ATP‐dependent corrinoid reduction determined by redox titrations with europium(II)–DTPA

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Redox chemistry of cobalamin and its derivatives

Cited by 94 publications

References 202 publications

The Reductive Cleavage Mechanism and Complex Stability of Glutathionyl‐Cobalamin in Acidic Media

The Reductive Cleavage Mechanism and Complex Stability of Glutathionyl‐Cobalamin in Acidic Media

Accumulation of NO2‐cobalamin in nutrient‐stressed ammonia‐oxidizing archaea and in the oxygen deficient zone of the eastern tropical North Pacific

Redox potential changes during ATP‐dependent corrinoid reduction determined by redox titrations with europium(II)–DTPA

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Accumulation of NO₂‐cobalamin in nutrient‐stressed ammonia‐oxidizing archaea and in the oxygen deficient zone of the eastern tropical North Pacific