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Ecotoxicology and Environmental Safety Dec 2022Chromium (Cr) is a harmful heavy metal that poses a serious threat to plants and animals. Selenium (Se) and molybdenum (Mo) are two beneficial elements for plant growth...
Chromium (Cr) is a harmful heavy metal that poses a serious threat to plants and animals. Selenium (Se) and molybdenum (Mo) are two beneficial elements for plant growth and resistance. However, their interactive effects on Cr uptake and distribution are poorly understood. Therefore, a hydroponics experiment was conducted to explore the effects of the use of Se and Mo alone and simultaneously on mitigating Cr toxicity. In this study, Nicotiana tabacum L. seedlings were exposed to control, 50 µM Cr, 50 μM Cr + 2 μM Se, 50 μM Cr + 1 μM Mo, or 50 μM Cr + 2 μM Se + 1 μM Mo in Hoagland solution. After 2 weeks, the plant biomass, Cr, Se and Mo contents, photosynthesis, leaf ultrastructure, antioxidant system, subcellular distribution and associated gene expression in Nicotiana tabacum L. were determined. The results showed that simultaneous use of Se and Mo promoted tobacco growth under Cr stress, as evidenced by reducing reactive oxygen species (ROS) content and reducing Cr translocation factor (TF) and inducing a 51.3% reduction in Cr content in shoots. Additionally, Se-Mo interactions increased the levels of glutathione (GSH) and phytochelatin (PC) and the distribution of Cr in the cell walls and organelles. Furthermore, the relative expression of PCS1 was upregulated, while those of NtST1 and MSN1 were downregulated. The results concluded that the simultaneous use of Se and Mo effectively alleviated Cr toxicity in Nicotiana tabacum L., which not only offers an efficient way for crops to resist Cr toxicity but also provides evidence for the benefit of Se combined with Mo.
Topics: Animals; Selenium; Molybdenum; Nicotiana; Chromium; Biological Transport; Glutathione
PubMed: 36455352
DOI: 10.1016/j.ecoenv.2022.114312 -
Molecules (Basel, Switzerland) Jul 2022A concise review is provided of the contributions that various spectroscopic methods have made to our understanding of the physical and electronic structures of... (Review)
Review
A concise review is provided of the contributions that various spectroscopic methods have made to our understanding of the physical and electronic structures of mononuclear molybdenum enzymes. Contributions to our understanding of the structure and function of each of the major families of these enzymes is considered, providing a perspective on how spectroscopy has impacted the field.
Topics: Electron Spin Resonance Spectroscopy; Molybdenum
PubMed: 35956757
DOI: 10.3390/molecules27154802 -
Molecules (Basel, Switzerland) Sep 2022Formate dehydrogenases (FDH) reversibly catalyze the interconversion of CO to formate. They belong to the family of molybdenum and tungsten-dependent oxidoreductases.... (Review)
Review
Formate dehydrogenases (FDH) reversibly catalyze the interconversion of CO to formate. They belong to the family of molybdenum and tungsten-dependent oxidoreductases. For several decades, scientists have been synthesizing structural and functional model complexes inspired by these enzymes. These studies not only allow for finding certain efficient catalysts but also in some cases to better understand the functioning of the enzymes. However, FDH models for catalytic CO reduction are less studied compared to the oxygen atom transfer (OAT) reaction. Herein, we present recent results of structural and functional models of FDH.
Topics: Carbon Dioxide; Formate Dehydrogenases; Formates; Molybdenum; Oxidation-Reduction; Oxygen; Tungsten
PubMed: 36144724
DOI: 10.3390/molecules27185989 -
Environmental Health and Preventive... May 2019Melanin is detectable in various sense organs including the skin in animals. It has been reported that melanin adsorbs toxic elements such as mercury, cadmium, and lead....
BACKGROUND
Melanin is detectable in various sense organs including the skin in animals. It has been reported that melanin adsorbs toxic elements such as mercury, cadmium, and lead. In this study, we investigated the adsorption of molybdenum, which is widely recognized as a toxic element, by melanin.
METHODS
Molybdenum level of the mouse skin was measured by inductively coupled plasma mass spectrometry. The pigmentation level of murine skin was digitalized as the L* value by using a reflectance spectrophotometer. An in vitro adsorption assay was performed to confirm the interaction between molybdenum and melanin.
RESULTS
Our analysis of hairless mice with different levels of skin pigmentation showed that the level of molybdenum increased with an increase in the level of skin pigmentation (L* value). Moreover, our analysis by Spearman's correlation coefficient test showed a strong correlation (r = - 0.9441, p < 0.0001) between L* value and molybdenum level. Our cell-free experiment using the Langmuir isotherm provided evidence for the adsorption of molybdenum by melanin. The maximum adsorption capacity of 1 mg of synthetic melanin for molybdenum was 131 μg in theory.
CONCLUSION
Our in vivo and in vitro results showed a new aspect of melanin as an adsorbent of molybdenum.
Topics: Adsorption; Animals; Melanins; Mice; Mice, Hairless; Mice, Transgenic; Molybdenum; Skin; Skin Pigmentation; Water Pollutants, Chemical
PubMed: 31101002
DOI: 10.1186/s12199-019-0791-y -
Chemical Reviews Jun 2020Biological nitrogen fixation is catalyzed by the enzyme nitrogenase, which facilitates the cleavage of the relatively inert triple bond of N. Nitrogenase is most... (Review)
Review
Biological nitrogen fixation is catalyzed by the enzyme nitrogenase, which facilitates the cleavage of the relatively inert triple bond of N. Nitrogenase is most commonly associated with the molybdenum-iron cofactor called FeMoco or the M-cluster, and it has been the subject of extensive structural and spectroscopic characterization over the past 60 years. In the late 1980s and early 1990s, two "alternative nitrogenase" systems were discovered, isolated, and found to incorporate V or Fe in place of Mo. These systems are regulated by separate gene clusters; however, there is a high degree of structural and functional similarity between each nitrogenase. Limited studies with the V- and Fe-nitrogenases initially demonstrated that these enzymes were analogously active as the Mo-nitrogenase, but more recent investigations have found capabilities that are unique to the alternative systems. In this review, we will discuss the reactivity, biosynthetic, and mechanistic proposals for the alternative nitrogenases as well as their electronic and structural properties in comparison to the well-characterized Mo-dependent system. Studies over the past 10 years have been particularly fruitful, though key aspects about V- and Fe-nitrogenases remain unexplored.
Topics: Models, Molecular; Molybdenum; Nitrogen; Nitrogen Fixation; Nitrogenase
PubMed: 32129988
DOI: 10.1021/acs.chemrev.9b00704 -
Redox Report : Communications in Free... Jan 2017This review summarizes the spectroscopic results, which will provide useful suggestions for future research. In addition, the fields that urgently need more information... (Review)
Review
OBJECTIVES
This review summarizes the spectroscopic results, which will provide useful suggestions for future research. In addition, the fields that urgently need more information are also advised.
BACKGROUND
Nitrite-NO-cGMP has been considered as an important signaling pathway of NO in human cells. To date, all the four known human molybdenum-containing enzymes, xanthine oxidase, aldehyde oxidase, sulfite oxidase, and mitochondrial amidoxime-reducing component, have been shown to function as nitrite reductases under hypoxia by biochemical, cellular, or animal studies. Various spectroscopic techniques have been applied to investigate the structure and catalytic mechanism of these enzymes for more than 20 years.
METHODS
We summarize the published data on the applications of UV-vis and EPR spectroscopies, and X-ray crystallography in studying nitrite reductase activity of the four human molybdenum-containing enzymes.
RESULTS
UV-vis has provided useful information on the redox active centers of these enzymes. The utilization of EPR spectroscopy has been critical in determining the coordination and redox status of the Mo center during catalysis. Despite the lack of substrate-bound crystal structures of these nitrite reductases, valuable structural information has been obtained by X-ray crystallography.
CONCLUSIONS
To fully understand the catalytic mechanisms of these physiologically/pathologically important nitrite reductases, structural studies on substrate-redox center interaction are needed.
Topics: Animals; Humans; Molybdenum; Nitric Oxide; Nitrite Reductases; Oxidation-Reduction
PubMed: 27686142
DOI: 10.1080/13510002.2016.1206175 -
Inorganic Chemistry Sep 2022The complex [TEA][Tp*Mo(O)(SBMOPP)] () [TEA = tetraethylammonium, Tp* = tris(3,5-dimethylpyrazolyl)hydroborate, and BMOPP = 6-(3-butynyl-2-methyl-2-ol)-2-pivaloyl...
The complex [TEA][Tp*Mo(O)(SBMOPP)] () [TEA = tetraethylammonium, Tp* = tris(3,5-dimethylpyrazolyl)hydroborate, and BMOPP = 6-(3-butynyl-2-methyl-2-ol)-2-pivaloyl pterin] is a structural analogue of the molybdenum cofactor common to all pyranopterin molybdenum enzymes because it possesses a pyranopterin-ene-1,2-dithiolate ligand (SBMOPP) that exists primarily in the ring-closed pyrano structure as a resonance hybrid of ene-dithiolate and thione-thiolate forms. Compound , the protonated [Tp*Mo(O)(SBMOPP-H)] () and one-electron-oxidized [Tp*Mo(O)(SBMOPP)] [] species have been studied using a combination of electrochemistry, electronic absorption, and electron paramagnetic resonance (EPR) spectroscopy. Additional insight into the nature of these molecules has been derived from electronic structure computations. Differences in dithiolene C-S bond lengths correlate with relative contributions from both ene-dithiolate and thione-thiolate resonance structures. Upon protonation of to form , large spectroscopic changes are observed with transitions assigned as Mo(xy) → pyranopterin metal-to-ligand charge transfer and dithiolene → pyranopterin intraligand charge transfer, respectively, and this underscores a dramatic change in electronic structure between and . The changes in electronic structure that occur upon protonation of are also reflected in a large >300 mV increase in the Mo(V/IV) redox potential for , resulting from the greater thione-thiolate resonance contribution and decreased charge donation that stabilize the Mo(IV) state in with respect to one-electron oxidation. EPR spin Hamiltonian parameters for one-electron-oxidized and uncyclized [Tp*Mo(O)(SBDMPP)] [] [BDMPP = 6-(3-butynyl-2,2-dimethyl)-2-pivaloyl pterin] are very similar to each other and to those of [Tp*MoO(bdt)] (bdt = 1,2-ene-dithiolate). This indicates that the dithiolate form of the ligand dominates at the Mo(V) level, consistent with the demand for greater S → Mo charge donation and a corresponding increase in Mo-S covalency as the oxidation state of the metal is increased. Protonation of represents a simple reaction that models how the transfer of a proton from neighboring acidic amino acid residues to the Mo cofactor at a nitrogen atom within the pyranopterin dithiolene (PDT) ligand in pyranopterin molybdenum enzymes can impact the electronic structure of the Mo-PDT unit. This work also illustrates how pyran ring-chain tautomerization drives changes in resonance contributions to the dithiolene chelate and may adjust the reduction potential of the Mo ion.
Topics: Electron Spin Resonance Spectroscopy; Ligands; Molybdenum; Pterins; Thiones
PubMed: 36000991
DOI: 10.1021/acs.inorgchem.2c01234 -
Biochimica Et Biophysica Acta Jun 2015The biosynthesis of the molybdenum cofactor (Moco) has been intensively studied, in addition to its insertion into molybdoenzymes. In particular, a link between the... (Review)
Review
The biosynthesis of the molybdenum cofactor (Moco) has been intensively studied, in addition to its insertion into molybdoenzymes. In particular, a link between the assembly of molybdoenzymes and the biosynthesis of FeS clusters has been identified in the recent years: 1) the synthesis of the first intermediate in Moco biosynthesis requires an FeS-cluster containing protein, 2) the sulfurtransferase for the dithiolene group in Moco is also involved in the synthesis of FeS clusters, thiamin and thiolated tRNAs, 3) the addition of a sulfido-ligand to the molybdenum atom in the active site additionally involves a sulfurtransferase, and 4) most molybdoenzymes in bacteria require FeS clusters as redox active cofactors. In this review we will focus on the biosynthesis of the molybdenum cofactor in bacteria, its modification and insertion into molybdoenzymes, with an emphasis to its link to FeS cluster biosynthesis and sulfur transfer.
Topics: Bacteria; Bacterial Proteins; Coenzymes; Iron-Sulfur Proteins; Metalloproteins; Models, Biological; Models, Chemical; Molecular Structure; Molybdenum; Molybdenum Cofactors; Oxidoreductases; Pteridines
PubMed: 25268953
DOI: 10.1016/j.bbamcr.2014.09.021 -
Annals of Botany Oct 2005The importance of molybdenum for plant growth is disproportionate with respect to the absolute amounts required by most plants. Apart from Cu, Mo is the least abundant... (Review)
Review
BACKGROUND
The importance of molybdenum for plant growth is disproportionate with respect to the absolute amounts required by most plants. Apart from Cu, Mo is the least abundant essential micronutrient found in most plant tissues and is often set as the base from which all other nutrients are compared and measured. Molybdenum is utilized by selected enzymes to carry out redox reactions. Enzymes that require molybdenum for activity include nitrate reductase, xanthine dehydrogenase, aldehyde oxidase and sulfite oxidase.
SCOPE
Loss of Mo-dependent enzyme activity (directly or indirectly through low internal molybdenum levels) impacts upon plant development, in particular, those processes involving nitrogen metabolism and the synthesis of the phytohormones abscisic acid and indole-3 butyric acid. Currently, there is little information on how plants access molybdate from the soil solution and redistribute it within the plant. In this review, the role of molybdenum in plants is discussed, focusing on its current constraints in some agricultural situations and where increased molybdenum nutrition may aid in agricultural plant development and yields.
CONCLUSIONS
Molybdenum deficiencies are considered rare in most agricultural cropping areas; however, the phenotype is often misdiagnosed and attributed to other downstream effects associated with its role in various enzymatic redox reactions. Molybdenum fertilization through foliar sprays can effectively supplement internal molybdenum deficiencies and rescue the activity of molybdoenzymes. The current understanding on how plants access molybdate from the soil solution or later redistribute it once in the plant is still unclear; however, plants have similar physiological molybdenum transport phenotypes to those found in prokaryotic systems. Thus, careful analysis of existing prokaryotic molybdate transport mechanisms, as well as a re-examination of know anion transport mechanisms present in plants, will help to resolve how this important trace element is accumulated.
Topics: Agriculture; Biological Transport; Carrier Proteins; Crops, Agricultural; Molybdenum
PubMed: 16033776
DOI: 10.1093/aob/mci226 -
The Journal of Biological Chemistry Mar 2022Sulfite oxidase (SOX) is a homodimeric molybdoheme enzyme that oxidizes sulfite to sulfate at the molybdenum center. Following substrate oxidation, molybdenum is reduced...
Sulfite oxidase (SOX) is a homodimeric molybdoheme enzyme that oxidizes sulfite to sulfate at the molybdenum center. Following substrate oxidation, molybdenum is reduced and subsequently regenerated by two sequential electron transfers (ETs) via heme to cytochrome c. SOX harbors both metals in spatially separated domains within each subunit, suggesting that domain movement is necessary to allow intramolecular ET. To address whether one subunit in a SOX dimer is sufficient for catalysis, we produced heterodimeric SOX variants with abolished sulfite oxidation by replacing the molybdenum-coordinating and essential cysteine in the active site. To further elucidate whether electrons can bifurcate between subunits, we truncated one or both subunits by deleting the heme domain. We generated three SOX heterodimers: (i) SOX/Mo with two active molybdenum centers but one deleted heme domain, (ii) SOX/Mo_C264S with one unmodified and one inactive subunit, and (iii) SOX_C264S/Mo harboring a functional molybdenum center on one subunit and a heme domain on the other subunit. Steady-state kinetics showed 50% SOX activity for the SOX/Mo and SOX/Mo_C264S heterodimers, whereas SOX_C264S/Mo activity was reduced by two orders of magnitude. Rapid reaction kinetics monitoring revealed comparable ET rates in SOX/Mo, SOX/Mo_C264S, and SOX/SOX, whereas in SOX_C264S/Mo, ET was strongly compromised. We also combined a functional SOX Mo domain with an inactive full-length SOX R217W variant and demonstrated interdimer ET that resembled SOX_C264S/Mo activity. Collectively, our results indicate that one functional subunit in SOX is sufficient for catalysis and that electrons derived from either Mo or Mo follow this path.
Topics: Electrons; Heme; Molybdenum; Protein Domains; Sulfite Oxidase; Sulfites
PubMed: 35120924
DOI: 10.1016/j.jbc.2022.101668