Reactions of aquacobalamin and cob(II)alamin with chlorite and chlorine dioxide

Article abstract of DOI:10.1007/s00775-016-1417-0

Reactions of aquacobalamin (H₂O–Cbl(III)) and its one-electron reduced form (cob(II)alamin, Cbl(II)) with chlorite (ClO₂ ^?) and chlorine dioxide (ClO₂ ^?) were studied by conventional and stopped-flow UV–Vis spectroscopies and matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS). ClO₂ ^? does not react with H₂O–Cbl(III), but oxidizes Cbl(II) to H₂O–Cbl(III) as a major product and corrin-modified species as minor products. The proposed mechanism of chlorite reduction involves formation of OCl^? that modifies the corrin ring during the course of reaction with Cbl(II). H₂O–Cbl(III) undergoes relatively slow destruction by ClO₂ ^? via transient formation of oxygenated species, whereas reaction between Cbl(II) and ClO₂ ^? proceeds extremely rapidly and leads to the oxidation of the Co(II)-center.

Full text of DOI:10.1007/s00775-016-1417-0

J Biol Inorg Chem
DOI 10.1007/s00775-016-1417-0
ORIGINAL PAPER
Reactions of aquacobalamin and cob(II)alamin with chlorite
and chlorine dioxide
Ilia A. Dereven’kov1 · Nikita I. Shpagilev1 · László Valkai2 · Denis S. Salnikov1 ·
Attila K. Horváth2,3 · Sergei V. Makarov1
Received: 28 September 2016 / Accepted: 14 November 2016
© SBIC 2016
Abstract Reactions of aquacobalamin (H2O–Cbl(III)) and
its one-electron reduced form (cob(II)alamin, Cbl(II)) with
chlorite (ClO2−) and chlorine dioxide (ClO•2) were studied
by conventional and stopped-flow UV–Vis spectroscopies
and matrix-assisted laser deso−rption/ionization-mass spec-
trometry (MALDI-MS). ClO2 does not react with H2O–
Cbl(III), but oxidizes Cbl(II) to H2O–Cbl(III) as a major
product and corrin-modified species as minor products. The
proposed mechanism of chlorite reduction involves forma-
tion of OCl− that modifies the corrin ring during the course
of reaction with Cbl(II). H2O–Cbl(III) undergoes rela-
tively slow destruction by ClO•2 via transient formation of
oxygenated species, whereas reaction between Cbl(II) and
ClO•2 proceeds extremely rapidly and leads to the oxidation
of the Co(II)-center.
Abbreviations
Cbl
DMBI
MALDI-MS Matrix-assisted laser desorption/ionization-
mass spectrometry
Cobalamin
5,6-Dimethylbenzimidazole
Introduction
Cobalamins (Cbl) are the most ubiquitous biocomplexes
of cobalt. Their structure includes a corrin ring equatori-
ally ligated to cobalt ion, nucleotide loop attached to lower
axial (α) site and numerous groups R bound to the upper
(β) site [1] (Fig. 1). In the course of redox events, cobalt
ion adopts 3+, 2+ and 1+ oxidation states [2–4].
Cobalamins play a crucial role in the metabolism of
homocysteine and l-methylmalonyl-CoA in mammals [5].
Impaired homocysteine metabolism is associated with an
increased risk of cardiovascular disease [6], neural tube
defects [7], and neurodegenerative diseases [8]. A defi-
ciency of l-methylmalonyl-CoA mutase is responsible for
an inherited disorder of metabolism which is one of the
causes of methylmalonic aciduria [9].
Keywords Vitamin B12 · Chlorite · Chlorine dioxide ·
Redox reactions · Kinetics
Electronic supplementary material The online version of this
article (doi:10.1007/s00775-016-1417-0) contains supplementary
material, which is available to authorized users.
Upon entering the cells, Cbl(III) can be reduced to Cbl(II)
prior to binding to the Cbl-dependent enzymes [10]. Reduced
Cbls are also involved in the methionine synthase (reversible
Co3+↔Co1+ conversion [11]) and l-methylmalonyl-CoA
mutase enzyme (Co3+↔Co2+ conversion [12]) cycles and
are sensitive to oxidation. Both B12-dependent enzymes are
inactivated under oxidative stress conditions [13].
* Ilia A. Dereven’kov
derevenkov@gmail.com
1
Institute of Macroheterocyclic Compounds, Ivanovo State
University of Chemistry and Technology, Sheremetevskiy
Str. 7, 153000 Ivanovo, Russian Federation
The chlorine oxyanions (ClO−, ClO2−, ClO3 and
−
ClO4−) as well as chlorine dioxide (ClO2•) have found
diverse application in various fields of industry. For a
long time, chlorite (ClO2−) was considered to have only
harmful effects in vivo. However, recent evidence changes
2
Department of Inorganic Chemistry, University of Pécs,
Ifjúság útja 6, 7624 Pécs, Hungary
3
János Szentágothai Research Center, Ifjúság útja 34,
7624 Pécs, Hungary
1 3

J Biol Inorg Chem
chlorite is an active substance in wound healing drugs like
Oxoferin and WF10 [32].
Hypochlorous acid (HOCl) is a potent oxidant gener-
ated by the myeloperoxidase/hydrogen peroxide/chloride
system [33]. HOCl has been associated with the develop-
ment of a variety of disorders such as inflammation, heart
disease, pulmonary fibrosis and cancer through its ability to
modify various biomolecules [34–37].
Chlorine dioxide is a well-known disinfectant [38]
used for water treatment [39] or food preservation [40].
In comparison to HOCl, ClO•2 possesses weaker oxidiz-
ing ability and induces damage of biological compounds
to a lesser extent [40]. However, reactions of ClO•2 with
thiols [41], phenols [42, 43], proteins [44, 45], guanosine
5′-monophosphate [46], dihydronicotinamide adenine
dinucleotide [47], tryptophan [48] and others have been
reported.
In spite of extensive long-term use of oxyhalogens and
their significant in vivo implications, their reactions with
Cbls have not been studied in detail. Hypochlorous acid
destroys cyanocobalamin [49] and dicyanocobinamide, its
analog lacking the nucleotide motif [50]. These reactions
are accompanied by oxidation of CN− and liberation of
cyanogen chloride (CNCl), a volatile toxic asphyxiant [51].
A recent study [52] reports that Cbl(II) is extremely reac-
tive toward HOCl. The interaction results in the formation
of a mixture of H2O/HO−–Cbl(III) and corrin-modified
products. Corrin modification in Cbl(II)/HOCl system was
also indicated earlier by Balasubramanian and Gould [53].
Kinetic studies on reaction between reduced Cbl species
and chlorite, chlorate, bromate and iodate have also been
performed [53]. Nevertheless, no data regarding the modi-
fication of corrin by these compounds were reported in the
latter reference.
Fig. 1 Structure of aquacobalamin. H2O is lost upon one-electron
reduction of H2OCbl to give pentacoordinate Cbl(II)
conventional views regarding its biological role. Chlorite
reacts with a variety of heme-containing enzymes. For
example, it induces the formation of methemoglobin [14]
and can act as a hydroxylating agent in cytochrome P450
[15]. Chlorite dismutases are found in bacteria and archaea
[16, 17] and convert chlorite to chloride (Cl−) and dioxy-
gen (O2) [18]. Several metal complexes mimicking chlo-
rite dismutase have been developed [19, 20], whereas the
reaction of chlorite with other metal complexes induces
the formation of chlorine dioxide, chloride and chlorate
[21–23].
Among heme peroxidases, chlorite can be utilized by
cytochrome c peroxidase [24], chloroperoxidase [25] and
horseradish peroxidase [26]. In contrast to horseradish per-
oxidase, human myeloperoxidase and bovine lactoperoxi-
dase are very susceptible to chlorite resulting in a rapid loss
of activity accompanied by heme bleaching [27]. Moreover,
other possible chlorite effects are modulation and stimula-
tion of immune responses [28], activation of macrophage
functions [29], the stimulation of killer cell cytotoxicity
[30] and methemoglobin formation [31]. In addition to that,
To understand the stability of vitamin B12 toward Cl-
based oxidants, we performed mechanistic studies on the
reaction of Cbl(II) and H2O–Cbl(III) with chlorite and
chlorine dioxide.
Experimental section
Reagents
Hydroxocobalamin hydrochloride (HOCbl; ≥96%) and cya-
nocobalamin (CNCbl; ≥98%) were received from Sigma
and used without further purification. Oxygen-free argon
was used to deoxygenate solutions. Cob(II)alamin was pre-
pared by reduction of HOCbl by sodium borohydride. An
excess of borohydride was quenched by adding acetone [54].
Trifluoroacetate-Cbl was prepared from CNCbl through the
decyanation step [55] and further purification by column
1 3

J Biol Inorg Chem
chromatography. Trifluoroacetato-Cbl was eluted from silica
using ethanol:water = 1:1 mixture containing CF3COOH
(1 mM). The product was characterized by UV–Vis spectro-
photometry and MALDI-MS. Absence of Cl− in the product
was checked by using chloride-selective electrode.
Results and discussion
Reaction of aquacobalamin and cob(II)alamin
with hypochlorite
Buffer solutions (phosphate, acetate, carbonate or
tetraborate) or sodium hydroxide were used to maintain a
constant pH during the course of the experiments. Stock
reagent solutions were prepared and handled in gastight
glassware. Ionic strength was adjusted to 0.1 M using
NaNO3 in all kinetic measurements.
Sodium chlorite (NaClO2; Sigma-Aldrich) was purified
according to the procedure reported previously [56]. The
chlorite content was determined spectrophotometrically
using extinction coefficient at 260 nm of 154 M−1 cm−1
[57]. Chlorine dioxide was prepared by the reaction of
NaClO2 with H2SO4 [58] and stored at 4 °C in the absence
of light. ClO•2 concentrations were standardized using an
extinction coefficient of 1250 M−1 cm−1 at 359 nm [59].
HOCl stock solutions were prepared as reported [60] and
standardized by iodometric titration.
During the preparation of this paper initially devoted to
the reactions of aquacobalamin and cob(II)alamin with
hypochlorite, chlorite and chlorine dioxide, the study
of the reaction between Cbl(II) and HOCl has been pub-
lished [52]. Dassanayake et al. performed their experiments
using phosphate buffer to determine the rate coefficient of
this reaction. It is, however, well known that in the case
of oxyhalogen species buffer assistance may contribute to
the overall kinetics; thus, the value of the rate coefficient
of the given reaction may depend on the type of buffer
applied [61]. Since our measurements have been carried
out in carbonate and tetraborate buffers as well it seemed
to be worthwhile to present the results of our independent
investigation.
Our data show that OCl− destroys HO−–Cbl(III), which
is in a good agreement with paper [52] (Figs. S1–S5). We
studied the kinetics of the reaction and found the presence
of two consecutive steps involving OCl− species in HO−–
Cbl(III) destruction mechanism (Figs. S2, S3). The origin
of these steps is discussed in SI. The value of rate constant
for the reaction between HOCl and H2O–Cbl(III) is found
Instrumentation
UV–Vis spectra were recorded on a cryothermostated
( 0.1 °C) Cary 50 UV–Vis spectrophotometer in sealed
quartz cells. Rapid reactions were studied on Applied Pho-
tophysics SX-20 diode array stopped-flow apparatus with a
single wavelength detection option. Kinetics of the oxida-
tion of Cbl(II) by chlorite and hypochlorite, and aquacobal-
amin (H2OCbl) by ClO•2 and HOCl was monitored at 475,
525 or 535 nm. Experimental data were analyzed using
Origin 7.5 software.
to be k1 (HOCl) = (37 2) M−1
s
−1, and that of the rate
constant for reaction between OCl− and HO−–Cbl(III) is
indistinguishable from zero. For the second step of the reac-
tion between corrin-modified species and HOCl and OCl−,
the values of rate constants are k2 (HOCl) = (4.3
−1 s−1 and k2(OCl−)–(0.4 0.1) M−1 s−1, respectively.
Our data on the reaction between Cbl(II) and OCl−
0.3)
M
Matrix assisted laser desorption/ionization-mass spec-
trometry (MALDI-MS) measurements were performed on
Shimadzu AXIMA Confidence mass spectrometer with
α-cyano-4-hydroxycinnamic acid (CHCA) as the matrix.
The pH values of solutions were determined using Mul-
titest IPL-103 pH-meter (SEMICO) equipped with ESK-
10601/7 electrode (Izmeritelnaya tekhnika) filled by 3.0 M
KCl solution. The electrode was preliminarily calibrated
using standard buffer solutions (pH 1.65–12.45).
(Figs. S6–S11) agree with that reported in [52]. The mech-
anism of the reaction is discussed in SI. We found the val-
ues of rate constants for oxidation of Cbl(II) by HOCl and
OCl−: k3(HOCl) = (1.7 0.1) 107 M−1 s−1 and k3 (OCl−)–
(8 2) 103 M−1 s−1 (25 °C). These values reported in [52]
are 2.6 × 107 and 2.3 × 103 M−1 s−1 (25 °C) for HOCl and
OCl−, respectively.
Determination of chloride concentrations was performed
using a Cl−-selective electrode (ELIT; NICO ANALIT).
Saturated silver chloride electrode (ESr-10101; Izmeritel-
naya tekhnika) was used as a reference. To avoid contam-
ination of sample by Cl−, a reference electrode was con-
nected with the solution examined through a salt bridge
containing concentrated KNO3 solution. The Cl−-selective
electrode was calibrated immediately before measurements
by standard KCl solutions.
Reaction of cob(II)alamin with chlorite
Addition of ClO2− to H2O/HO−–Cbl(III) does not result in
changes in the UV–Vis spectrum at pH 4–13 within sev-
eral hours. The reaction between Cbl(II) and ClO2 has
been studied earlier in acidic medium in a quite narrow
pH range (2.4–3.7) [53]. In this work, this interaction was
investigated in weakly acidic, neutral and alkaline medium.
Changes in UV–Vis spectrum after mixing chlorite with
−
1 3

J Biol Inorg Chem
Fig. 3 UV–Vis spectra recorded during titration of Cbl(II)
(9.0 × 10−5 M) by ClO2− at pH 5.6 and 25 °C. Inset: plot of absorb-
ance at 525 nm vs. ratio of initial concentrations ClO2−/Cbl(II)
Fig. 2 UV–Vis spectra of the reaction between Cbl(II) (5 × 10−5 M)
and chlorite (5 × 10−4 M) at pH 7.6, 25 °C
Cbl(II) are shown in Fig. 2, i.e., increase of absorbance at
352 and 530 nm is observed. The spectrum of the product
is slightly different from that of H2O/HO−–Cbl(III) at the
same pH (Fig. S12). The separation of the reaction mixture
on a silica column indicates that H2O–Cbl(III) (ca. 90%
yield) is a major reaction product and the minor fraction
is represented by a product of which the UV–Vis spectrum
includes an absorption peak at 460 nm (Fig. S13), typical
for so-called “stable yellow corrinoids” (corrin-modified
complexes) [62]. The formation of corrin-modified prod-
ucts is also supported by MALDI-MS measurements: peaks
at 1345 and 1383, corresponding to [Cbl(III) + O]+ and
[Cbl(III) + O – H+ + K+]+ ions are observed (Fig. S14).
It is important to note that these peaks are completely the
same as those for the reaction taking place between Cbl(II)
and ClO−. Formation of corrin-modified products was not
indicated in an earlier study [53].
same reaction order with respect to Cbl(II) is observed at
higher pH values. The addition of chloride ion has a neg-
ligible effect on the shape of the kinetic curves (Fig. S16);
thus, the reaction between Cbl(II) and HOCl (which rap-
idly reacts with Cl−) does not contribute to the kinet-
ics. Dependence of the observed rate constants (kobs.4) on
[ClO2−] is linear and indicates a formal kinetic order of one
with respect to chlorite (Fig. 4b).
A plot of k′4 (k′4 corresponds to the slope of dependence
of kobs.4 on ClO2− concentration) is shown in Fig. 5, i.e., the
reaction rate decreases upon alkalinization of the medium,
but does not tend to zero. To explain this pH dependence,
a kinetically active species of the oxidant can be suggested,
viz., ClO2− and HClO2 (reaction 1; pKa = 1.74, 25 °C [60]).
Using Eq. (2), the following values for the corresponding
rate constants were found: k4 (ClO2−) = (21 2) M−1 s−1
(for the reaction with ClO2−) and k4(HClO2) = (5.3 0.3)·
106 M−1 s−1 (for the reaction with HClO2). Both ClO2− and
HClO2 as oxidants of Cbl(II) were suggested in [53], but th−e
reported value for the reaction between Cbl(II) and ClO2
of ca. 2 × 104 M−1 s−1 (25 °C; I = 0.52 M (LiClO4)) [53]
is substantially higher than our data. This discrepancy can
result from very narrow pH range or low purity of sodium
chlorite used by the authors [53].
To determine the stoi−chiometry of the reaction, titra-
tion of Cbl(II) by ClO2 was performed under weakly
acidic (pH 5.6; Fig. 3) and weakly alkaline (pH 9.2; Fig.
S15) conditions. In both cases, the ratio of initial concen-
−
trations Cbl(II): ClO2 = 3: 1 was established. Measure-
ments with chloride ion-selective electrode showed that
ClO2− was completely reduced to Cl− during the course of
the reaction. It should also be mentioned that the reduction
ClO−2 + H+ ↔ HClO2,
(1)
−
of ClO2 to Cl− requires four electrons. Therefore, it can
be concluded that during the course of the reaction with
cob(II)alamin, ClO2 receives three electrons from Co(II)
k4(HClO2) · 10−pH
−
k4′ =
+ k4(ClO−2 ).
2
(2)
10−pH + 10−pK (HClO )
a
ions and one from corrin. The interaction of chlorite reduc-
tion products with corrin is supported by the formation of a
minor fraction of “stable yellow corrinoids”.
Next, the kinetic−s of the reaction between Cbl(II) and
an excess of ClO2 was investigated. A typical kinetic
curve (Fig. 4a) is described by a first-order equation. The
On the basis of the experimental and published [60]
data, the following mechanism of reduction of chlorite by
cob(II)alamin can be proposed. In the first step, one elec-
tron reduction of ClO2− or HClO2 proceeds (reaction 3). A
probable product of this reaction is the highly reactive ClO•
1 3

J Biol Inorg Chem
Fig. 4 Typical kinetic curve of the reaction between Cbl(II) (4 × 10−5 M) and ClO2− (5 × 10−4 M) at pH 7.5, 25 °C (a) and a plot of kobs.4 vs.
ClO2− concentration for the reaction (b)
−
Fig. 5 Plot of k’4 vs. pH for the reaction between Cbl(II) and ClO2
at 25 °C
Fig. 6 UV–Vis spectra of the reaction between H2O–Cbl(III)
(6 × 10−5 M) with ClO•2 (1 × 10−3 M) at pH 4.5 and 25 °C. Inset:
typical kinetic curve of the reaction
−
radical capable of readily oxidizing ClO2 to give OCl−
and ClO•2 (reaction 4; rate constant is 109 M−1 s−1 [63, 64]).
A rapid reduction of ClO• (reaction 5) by Cbl(II) can also
lead to the formation of hypochlorite. The following reac-
tions (6, 7) of Cbl(II) with hypochlorite result in partial
modification of corrin and explain the formation of a minor
fraction of “stable yellow corrinoids”. Chlorine dioxide is
also capable of oxidizing Cbl(II) (reaction 8) that is stud-
ied in “Reaction of aquacobalamin and Cob(II)alamin with
chlorine dioxide” of “Results and discussion”. Reactions
(6, 7) explain the deviation of experimentally found stoi-
ClO• + ClO2− → OCl− + ClO•2,
(4)
Cbl(II) + ClO• → H2O−Cbl(III)/HO−−Cbl(III) + ClO−,
(5)
Cbl(II) + HOCl/OCl−(+H+) → H2O−Cbl(III)/
HO−−Cbl(III) + Cl−(or Cl•) + HO•(or HO−),
(6)
H2O−Cbl(III)/HO−−Cbl(III) + Cl•(or HO•)
−
chiometry Cbl(II): ClO2 = 3: 1 from expected 4: 1 one,
(7)
→ modified products,
since Cbl(II) reacts with ClO− in 1: 1 ratio ([52], Fig. S8).
Cbl(II) + ClO•2 → H2O−Cbl(III)/HO−−Cbl(III) + ClO−2 .
Cbl(II) + ClO−2 (or HClO2)( + H+)
(8)
→ H2O−Cbl(III)/HO−−Cbl(III) + ClO•,
(3)
1 3

J Biol Inorg Chem
Reaction of aquacobalamin and cob(II)alamin
with chlorine dioxide
The reaction of H2O–Cbl(III) with ClO•2 is accompanied
by changes in the UV–Vis spectrum shown in Fig. 6. The
presence of two consecutive steps is observed: the UV–Vis
spectrum of a product of a first step includes the maxima
at 537 and 560 nm and within a second step bleaching of
the solution occurs. MALDI-MS spectrum of the reaction
mixture shows the presence of peaks at 1361 and 1394
(Fig. S17), which can be attributed to [Cbl(III) + 2O]+ and
[Cbl(III) + 4O + H]+. Thus, within the reaction between
H2O–Cbl(III) and ClO•2 multiple incorporation of oxygen
atoms takes place.
The typical kinetic curve of the reaction is described by
two-exponential function (Fig. 6) that suggests presence of
two consecutive reactions in the system. The dependencies
of the observed rate constants for the first (kobs.5) and sec-
ond (kobs.6) steps on ClO•2 concentration are linear (Fig. 7)
and indicate intercepts indistinguishable from zero that
shows a formal kinetic order of one with respect to ClO•2 for
both steps. The values of the rate constants for the first and
second steps are k′5(ClO•2) = (3.0 0.1) 10−1 M−1 s−1 and
k′6 (ClO•2) = (2.9 0.1) 10−2 M−1 s−1 (25 °C), respectively.
In contrast to a relatively slow reaction of ClO•2 with
H2O–Cbl(III), an interaction of ClO•2 with Cbl(II) proceeds
extremely rapidly and cannot be studied by stopped-flow
spectroscopy. A final product of the reaction at pH 8 is HO−–
Cbl(III)/H2O–Cbl(III) (Fig. 8). Stoichiometry of the rapid
reaction was found to be Cbl(II): ClO•2 = 1:1 (a next slower
step was not taken into account, since it involves interaction
of Cbl(II) with a reduction product of chlorine dioxide). It
straightforwardly indicates that one-electron reduction of
ClO•2 takes place and ClO2− is formed (reaction 8).
Fig. 7 Plots of kobs.5 (filled square) and kobs.6 (filled circle) vs. ClO2•
concentration for the reaction between Cbl(II) (6 × 10−4 M) with
ClO•2 at pH 4.5 and 25 °C
Fig. 8 UV–Vis spectra recorded during titration of Cbl(II) by ClO•2.
Inset: plot of absorbance at 535 nm vs. ratio of initial concentrations
of ClO•2/Cbl(II), pH 8.0, 4.0 × 10−5 M Cbl(II) and 25 °C
Conclusions
This study demonstrated that aquacobalamin and its one-
electron reduced form (cob(II)alamin) possess stability
toward chlorite and chlorine dioxide, different from that
toward hypochlorite. H2O–Cbl(III) undergoes destruc-
tion by hypochlorite via formation of chlorinated species
and their further decomposition, whereas Cbl(II) is rap-
idly oxidized by hypochlorite to a mixture of H2O–Cbl(III)
and modified products [52]. These reactions can be impor-
tant for the in vivo effects accompanied by the formation
of OCl− as well as for the use of OCl− as disinfectant.
Thus, large amounts of OCl− and a simultaneous presence
of reductants being capable of reducing Co(III) to Co(II)
can potentially induce a significant loss of vitamin B12.
H2O–Cbl(III) was shown to be resistant toward reactions
the formation of H2O–Cbl(III) as a major reaction product
and corrin-modified species as a b−y-product. The proposed
mechanism of reduction of ClO2 involves formation of
chlorine species (e.g., OCl−) being much more reactive
than the initial compound and capable of modifying cor-
rin. Therefore, decomposition of vitamin B12 by chlorite is
almost negligible and can be relevant only for the condi-
tions when cobalamin exists in reduced form. Decomposi-
tion of H2O–Cbl(III) by ClO•2 proceeds at a relatively low
rate, whereas ClO•2 oxidizes Cbl(II) readily to H2O–Cbl(III)
with no modifications of the macrocycle. Thus, destruction
of vitamin B12 by ClO•2 should be taken into account only
during a prolonged exposure of a large concentration of
this disinfectant and preservative.
−
with ClO2−. Interaction of Cbl(II) with ClO2 results in
1 3

J Biol Inorg Chem
30. Kühne L, Konstandin M, Samstag Y, Meuer S, Giese T, Watzl C
(2011) J Biomed Biotechnol. doi:10.1155/2011/436587
31. Habermann E, Muller B (1989) Klin Wochenschr 67:20–25
32. McGrath MS, Kahn JO, Herndier BG (2002) Curr Opin Investig
Drugs 3:365–373
Acknowledgements This work was supported by the Russian Sci-
ence Foundation, Agreement no. 14-23-00204. The financial sup-
port of the Hungarian Research Fund (NKFIH-OTKA) Grant No.
K116591 is gratefully acknowledged.
33. Malech HL, Gallin JI (1987) N Engl J Med 317:687–694
34. Pullar JM, Vissers MC, Winterbourn CC (2000) IUBMB Life
50:259–266
References
35. Pennathur S, Heinecke JW (2007) Antioxid Redox Signal
9:955–969
36. Davies MJ, Hawkins CL, Pattison DI, Rees MD (2008) Antioxid
Redox Signal 10:1199–1234
37. Goud AP, Goud PT, Diamond MP, Gonik B, Abu-Soud HM
(2008) Free Radic Biol Med 44:1295–1304
38. Noszticzius Z, Wittmann M, Kály-Kullai K, Beregvári Z, Kiss I,
Rosivall L, Szegedi J (2013) PLOS One 8. doi:10.1371/journal.
pone.0079157
1. Banerjee R, Ragsdale SW (2003) Annu Rev Biochem 72:209–247
2. Kräutler B (2005) Biochem Soc Trans 33:806–810
3. Dereven’kov IA, Salnikov DS, Silaghi-Dumitrescu R, Makarov
SV, Koifman OI (2016) Coord Chem Rev 309:68–83
4. Giedyk M, Goliszewska K, Gryko D (2015) Chem Soc Rev
44:3391–3404
5. Randaccio L, Geremia S, Demitri N, Wuerges J (2010) Mol-
ecules 15:3228–3259
39. Tzanavaras PD, Themelis DG, Kika FS (2007) Cent Eur J Chem
5:1–12
6. Nygard O, Vollset SE, Refsum H, Brattstrom L, Ueland PM
(1999) J Intern Med 246:425–454
40. Gómez-López VM, Rajkovic A, Ragaert P, Smigic N, Dev-
lieghere F (2009) Trends Food Sci Tech 20:17–26
41. Ison A, Odeh IN, Margerum DW (2006) Inorg Chem
45:8768–8775
42. Napolitano MJ, Green BJ, Nicoson JS, Margerum DW (2005)
Chem Res Toxicol 18:501–508
43. Aguilar CAH, Narayanan J, Manoharan M, Singh N, Thangarasu
P (2013) Aust J Chem 66:814–824
44. Ogata N (2007) Biochemistry 46:4898–4911
45. Sharma VK, Sohn M (2012) Environ Chem Lett 10:255–264
46. Napolitano MJ, Stewart DJ, Margerum DW (2006) Chem Res
Toxicol 19:1451–1458
7. Varela-Moreiras G, Murphy MM, Scott JM (2009) Nut Rev
67:S69–S72
8. Seshadri S, Beiser A, Selhub J, Jacques PF, Rosenberg IH,
D’Agostino RB, Wilson PW, Wolf PA (2002) N Engl J Med
346:476–483
9. Takahashi-Iniguez T, Garcia-Arellano H, Trujillo-Roldan MA,
Flores ME (2011) Biophys Res Commun 404:443–447
10. Banerjee R, Gherasim C, Padovani D (2009) Curr Opin Chem
Biol 13:484–491
11. Gruber K, Kratky C (2011) Cobalamin-Dependent Methio-
nine Synthase. In: Encyclopedia of Inorganic and Bioinorganic
Chemistry. Wiley
47. Bakhmutova-Albert EV, Margerum DW, Auer JG, Applegate BM
(2008) Inorg Chem 47:2205–2211
48. Stewart DJ, Napolitano MJ, Bakhmutova-Albert EV, Margerum
DW (2008) Inorg Chem 47:1639–1647
49. Abu-Soud HM, Maitra D, Byun J, Eduardo C, Souza A, Baner-
jee J, Saed GM, Diamond MP, Andreana PR, Pennathur S (2012)
Free Radic Biol Med 52:616–625
12. Gruber K, Kratky C (2011) Methylmalonyl CoA Mutase. In:
Encyclopedia of Inorganic and Bioinorganic Chemistry. Wiley
13. Padovani D, Banerjee R (2006) Biochemistry 45:9300–9306
14. French CL, Yaun SS, Baldwin LA, Leonard DA, Zhao XQ, Cala-
brese EJ (1995) J Appl Toxicol 15:167–174
15. Hrycay EG, Gustafsson JA, Ingelman-Sundberg M, Ernster L
(1975) FEBS Lett 56:161–165
50. Maitra D, Ali I, Abdulridha RM, Shaeib F, Khan SN, Saed GM,
Pennathur S, Abu-Soud HM (2014) PLOS One 9. doi:10.1371/
journal.pone.0110595
51. Szinicz L (2005) Toxicology 214:167–181
52. Dassanayake RS, Farhath MM, Shelley JT, Basu S, Brasch NE
(2016) J Inorg Biochem 163:81–87
53. Balasubramanian PN, Gould ES (1984) Inorg Chem
23:3689–3693
54. Brown KL, Hakimi JM, Nuss DM, MontejanoYD, Jacobsen DW
(1984) Inorg Chem 23:1463–1471
16. van Ginkel CG, Rikken GB, Kroon AG, Kengen SW (1996)
Arch Microbiol 166:321–326
17. Mlynek G, Sjoblom B, Kostan J, Fureder S, Maixner F, Gysel
K, Furtmüller PG, Obinger C, Wagner M, Daims H, Djinovic-
Carugo K (2011) J Bacteriol 193:2408–2417
18. Lee AQ, Streit BR, Zdilla MJ, Abu-Omar MM, DuBois JL
(2008) Proc Natl Acad Sci USA 105:15654–15659
19. Zdilla MJ, Lee AQ, Abu-Omar MM (2008) Angew Chem Int Ed
47:7697–7700
20. Zdilla MJ, Lee AQ, Abu-Omar MM (2009) Inorg Chem
48:2260–2268
55. Ivlev PA, Salnikov DS (2014) Dereven’kov IA. Acta Metal-
lomica 11:39–51
56. Peintler G, Nagypál I, Epstein IR (1990) J Phys Chem
94:2954–2958
21. Umile TP, Wang D, Groves JT (2011) Inorg Chem 50:10353–10362
22. Hu Z, Du H, Man W-L, Leung C-F, Liang H, Lau T-C (2012)
Chem Commun 48:1102–1104
57. Furman CS, Margerum DW (1998) Inorg Chem 37:4321–4327
58. Jakopitsch C, Spalteholz H, Furtmüller PG, Arnhold J, Obinger
C (2008) J Inorg Biochem 102:293–302
59. Chen T (1967) Anal Chem 39:804–813
60. Kormányos B, Nagypál I, Peintler G, Horváth AK (2008) Inorg
Chem 47:7914–7920
23. Hicks SD, Xiong S, Bougher CJ, Medvedev GA, Caruthers J,
Abu-Omar MM (2015) J Porphyr Phthalocyanines 19:492–499
24. George P (1953) J Biol Chem 201:413–426
25. Shahangian S, Hager LP (1981) J Biol Chem 256:6034–6040
26. Hollenberg PF, Rand-Meir T, Hager LP (1974) J Biol Chem
249:5816–5825
61. Jia Z, Margerum DW, Francisco JS (2000) Inorg Chem
39:2614–2620
62. Pratt JM (1972) Inorganic Chemistry of Vitamin B
12. Academic
27. Jakopitsch C, Pirker KF, Flemmig J, Hofbauer S, Schlorke D,
Furtmüller PG, Arnhold J, Obinger C (2014) J Inorg Biochem
135:10–19
28. Giese T, McGrath MS, Stumm S, Schempp H, Elstner E, Meuer
SC (2004) Cell Immunol 229:149–158
29. Veerasarn V, Boonnuch W, Kakanaporn C (2006) Gynecol Oncol
100:179–184
Press, London
63. Horváth AK, Nagypál I, Peintler G, Epstein IR, Kustin K (2003)
J Phys Chem A 107:6966–6973
64. Kläning UK, Sehested K (1991) J Phys Chem 95:740–743
1 3