Search Results (85)

Salmonella in gut habitats have traditionally been thought to conserve energy for growth via fermentation. However, recent reports indicate that ingested Salmonella can stimulate host-derived nitrate accumulation in the mucosal microenvironment, thereby enabling growth through nitrate respiration. Sodium tungstate is an effective treatment that inhibits the growth of certain nitrate-respiring bacteria, including Escherichia coli, Paracoccus and Proteus, when cultured under gut simulating conditions or within the gut of experimentally treated mice. This inhibitory effect is hypothesized to occur by inactivation of molybdenum-containing enzymes required for nitrate metabolism. Information is lacking on whether tungstate can inhibit the growth of Salmonella, particularly in the presence of culturable gut microbiota. Therefore, the objectives of this study were to evaluate the effects of sodium tungstate on Salmonella during pure culture or when cultured with freshly collected bovine rumen microbiota and to assess its impact on fermentation as well as nitrate and nitrite metabolism within the rumen microbial cultures. Our results indicate that 50 mM sodium tungstate treatment, whether alone or in combination with 5 mM nitrate, markedly increased the growth of Salmonella serovars Newport, Dublin and Typhimurium during pure culture. Moreover, during in vitro incubation, increased growth of experimentally inoculated S. Newport as well as wildtype E. coli and lactic acid bacteria was observed with ruminal microbiota treated with 100 mM tungstate when compared to non-tungstate-treated controls. Effects of tungstate on nitrate and nitrite metabolism were as expected during pure and mixed culture. When cultured with reduced tungsten rather than tungstate, the latter being bound to four oxygen atoms, an inhibitory effect on the growth of S. Newport was observed and effects on nitrate and nitrite metabolism were consistent with those observed with tungstate. These results suggest that, under conditions used in the present experiments, tungstate may have served as a source of oxygen for respiration above that achieved with nitrate alone. While this hypothesis has yet to be proven, it is supported by an adverse effect of tungstate, whether alone or in combination with 5 mM nitrate, on methane and volatile fatty acid production by the ruminal microbiota when compared to untreated or nitrate-only-treated microbiota. Full article

Anaerobic biodegradation of aromatic contaminants is constrained by unfavorable thermodynamics in the absence of oxygen and high activation energy required for aromatic ring-cleavage. Thus, identifying factors that enhance anaerobic aromatic degradation by microorganisms such as the Geotalea daltonii strain FRC-32 is crucial. Trace elements (TEs) function as rate-limiting cofactors for anaerobic carbon catabolism enzymes. Cobalt, molybdenum, selenite, and tungsten amendments stimulated G. daltonii growth on benzoate and anaerobic benzoate oxidation. To elucidate mechanisms of cobalt amendments in G. daltonii, we characterized a putative cobalt-specific energy-coupling factor (ECF) transporter CbiMNQO. The cbiMNQO genes form an operon and were upregulated under cobalt limitation, indicating a role in cobalt homeostasis. In silico structural predictions of CbiMNQO, ligand binding predictions of CbiMN, and alignment to known cobalt transporters suggested that CbiMNQO facilitates cobalt transport in G. daltonii. Structural and ligand binding predictions of BamB and BamF, and transcript-level analyses indicated that bamB and bamF, encoding molybdenum- and selenite–tungsten-dependent benzoyl-CoA reductase-subunits, modulate TE-dependent anaerobic benzoate degradation. Regulation of bamB and bamF in response to TE amendments corresponded with enhanced anaerobic benzoate oxidation, indicating stimulated benzoate dearomatization. Collectively, our findings demonstrated that TE amendments enhance anaerobic aromatic metabolism in G. daltonii and may contribute to anaerobic bioremediation. Full article

The accumulation of proline, an important osmoprotective and antioxidant compound, is a key defense mechanism induced in plants in response to stress factors, including salinity, and is likely dependent on abscisic acid (ABA). However, in barley grown for 8 days under salinity conditions (125 mM NaCl), proline accumulation was not accompanied by changes in ABA content. Co-application of 0.5 mM molybdenum (Mo) significantly reduced NaCl-induced oxidative stress, as measured by H₂O₂, O₂⁻, MDA, and chlorophyll content, and increased the activity of Mo-containing aldehyde oxidase (AO), an enzyme involved in de novo ABA synthesis. As a result, elevated ABA levels were observed, but proline content under salinity conditions was similar in Mo-treated and non-Mo-treated plants. In contrast, exposing plants to 0.5 mM tungsten (W), an antagonist of Mo, inhibited AO activity without significantly altering ABA content, while proline and oxidative stress marker levels increased dramatically under both non-saline and saline conditions. The observed changes in proline content are mainly due to modulation of the rate of synthesis and, to a lesser extent, the rate of degradation, as revealed by transcript abundance of P5CS1 and PDH, which encode D1-pyrroline-5-carboxylate synthetase and proline dehydrogenase, respectively. The results indicate that in barley grown under salinity conditions, proline accumulation is ABA-independent but depends on the level of oxidative stress modulated by Mo and W ions. Full article

Cancer remains a severe global health threat, with traditional therapies often plagued by limited efficacy and significant side effects. The emergence of nanotechnology, particularly metal-doped nanomaterials, offers a promising avenue for integrating diagnostic and therapeutic functions into a single platform, enabling a theranostic approach to oncology. This article explores the design and application of various metal-doped nanosystems, including gadolinium-doped selenium molybdenum nanosheets for magnetic resonance/photoacoustic dual-mode imaging and photothermal therapy, and metal-doped hollow mesoporous silica nanoparticles that leverage the tumor’s acidic microenvironment to release ions for catalytic generation of reactive oxygen species. Despite their promise, the limited enzyme-like activity of some nanozymes, insufficient endogenous hydrogen peroxide in tumors, and the tumor microenvironment’s defensive mechanisms, such as high glutathione levels, can restrict therapeutic efficacy. Looking forward, the outlook for the field is contingent upon advancing material engineering strategies. Future research should prioritize the development of intelligent, multifunctional nanoplatforms that can dynamically respond to and remodel the tumor microenvironment. Innovations in surface modification for enhanced targeting, alongside rigorous preclinical studies focused on safety and standardized manufacturing, are crucial for bridging the gap between laboratory research and clinical application, ultimately paving the way for personalized cancer medicine. Full article

Melatonin, a key regulator of the circadian rhythm, exerts strong antioxidant effects by scavenging reactive oxygen species (ROS) and modulating enzymatic redox balance. Xanthine oxidoreductase (XOR), a molybdenum- and iron–sulfur-containing enzyme, catalyzes the oxidation of hypoxanthine to xanthine and xanthine to uric acid—the final steps of purine catabolism—serving as an important enzymatic source of ROS under physiological conditions. XOR exists in three interconvertible isoforms: xanthine dehydrogenase (XDH), which uses NAD⁺ as an electron acceptor; xanthine oxidase (XO), which transfers electrons to oxygen, producing superoxide and hydrogen peroxide; and an intermediate form (XDO) that reflects the redox-dependent interconversion between the two. This study aimed to evaluate temporal and sex-dependent variations in XOR isoforms and their relationship with melatonin levels in healthy individuals. Sixty-six volunteers (33 women aged 24–38 and 33 men aged 24–44) were examined. Blood samples were collected at 02:00, 08:00, 14:00, and 20:00. Serum melatonin was measured using ELISA, and XOR isoform activities were determined spectrophotometrically. Melatonin exhibited a precise 24 h rhythm with a nocturnal peak at 02:00 (~98 pg/mL) and a daytime nadir at 14:00 (~9 pg/mL). XO activity varied significantly (p < 0.01), showing an inverse correlation with melatonin in men (ρ = −0.52, p = 0.006), while XDO activity correlated positively with melatonin in women at 14:00 (ρ = 0.48, p = 0.01). These findings indicate sex-specific and time-dependent regulation of XOR isoforms, suggesting that redox homeostasis is modulated differently in men and women throughout the day. Understanding these dynamics may refine the interpretation of oxidative stress biomarkers and help optimize diagnostic and chronotherapeutic approaches in redox-related disorders. Full article

The nitrogen cycle (N-cycle) is a cornerstone of global biogeochemistry, regulating nitrogen availability and affecting atmospheric chemistry, agricultural productivity, and ecological balance. Central to this cycle is the reversible interplay between nitrate (NO₃⁻) and nitrite (NO₂⁻), mediated by molybdenum-dependent enzymes—Nitrate reductases (NARs) and Nitrite oxidoreductases (NXRs). Despite catalyzing opposite reactions, these enzymes exhibit remarkable structural and mechanistic similarities. This review aims to elucidate the molecular underpinnings of nitrate reduction and nitrite oxidation by dissecting their enzymatic architectures, redox mechanisms, and evolutionary relationships. By focusing on recent structural, spectroscopic, and thermodynamic data, we explore how these two enzyme families represent “two sides of the same coin” in microbial nitrogen metabolism. Special emphasis is placed on the role of oxygen atom transfer (OAT) as a unifying mechanistic principle, the influence of environmental redox conditions, and the emerging evidence of bidirectional catalytic potential. Understanding this dynamic enzymatic interconversion provides insight into the flexibility and resilience of nitrogen-transforming pathways, with implications for environmental management, biotechnology, and synthetic biology. Full article

This short review provides an overview of the bioinorganic chemistry of molybdenum and tungsten, offering insights into current research perspectives and fundamental concepts in the field, as well as gaps in our knowledge. It is designed to highlight areas where future research is needed to fully elucidate the mechanisms of molybdenum- and tungsten-dependent enzymes and their broader significance in biochemistry and bioinorganic chemistry. It also provides an accessible introduction for senior undergraduate students and novice postgraduate researchers who are new to the field of bioinorganic chemistry. Towards this end, illustrative examples are presented, showcasing the essential roles these metals play in biological systems, their coordination chemistry, and their catalytic functions in metalloenzymes. Full article

Molybdenum (Mo) is a vital micronutrient for nearly all living organisms, serving as a cofactor for molybdoenzymes that catalyze essential redox reactions in nitrogen metabolism. Among these enzymes, nitrate reductase plays a crucial role in nitrate assimilation. Maintaining Mo homeostasis—including uptake, storage, and utilization—is critical to avoid both deficiency and toxicity. Our research focuses on uncovering novel molecular components involved in Mo homeostasis, particularly in connection with nitrate assimilation, using Chlamydomonas reinhardtii, a model green microalga. To achieve this, we generated more than 5000 Chlamydomonas transformants through insertional mutagenesis using a paromomycin resistance cassette (AphVIII) and screened them for altered growth on nitrate and under different Mo concentrations. We identified four strains showing altered growth patterns when using nitrate as a nitrogen source or exhibiting increased sensitivity or resistance to Mo. The genomic alterations in these strains were identified. Notably, both a Mo-resistant and a Mo-sensitive transformant had disruptions in the genes that encoded ABC-type transport proteins, indicating a potential role for these proteins in Mo transport. Additionally, two strains were unable to grow on nitrate. One of them had a mutation in the CNX7, a gene involved in Mo cofactor biosynthesis, while the other had a mutation in BAT1, an amino acid transporter. The BAT1 mutant represents an interesting case study, as this gene has not previously been associated with nitrate metabolism. These findings enhance our understanding of Mo and nitrate homeostasis mechanisms and open new paths for engineering microalgae with improved nitrogen assimilation. Full article

The determination of tungsten oxidation states and W–ligand bond lengths for pyranopterin tungsten enzymes can be negatively impacted by Fourier series termination effects and photodamage/photoreduction in the X-ray beam. As a result, a new set of bond valence sum (BVS) parameters have been derived from bond length data on W(+4) and W(+6) model compounds that were obtained from X-ray crystallography. These new W enzyme-specific BVS parameters have been used in the analysis of pyranopterin tungsten enzyme structural data. The results of this analysis indicate that there are potential issues with the enzyme crystal structures, including the number of ligating atoms to the tungsten atom, the W–ligand bond lengths, and the W oxidation state. We conclude that a BVS analysis of crystallographic and EXAFS structural data will help address these issues, and EXAFS should be more routinely employed in the determination of pyranopterin tungsten enzyme active site structures due to the increased accuracy of this technique for the determination of W–ligand bond distances. Full article

Skin aging is accelerated by inflammation processes generated by oxidative stress and external factors such as UV radiation. Plants belonging to the genus Kalanchoe that are rich sources of antioxidants could potentially strengthen the skin barrier if used as ingredients in cosmetic formulations. However, their use is limited due to the contents of bufadienolides, known cardiotoxins. This study aimed to establish a semi-quantitative profile of bufadienolides in the juices of K. blossfeldiana, K. daigremontiana, and K. pinnata using UHPLC combined with charged aerosol detection (CAD) and high-resolution mass spectrometry (HR-MS). Additionally, the study determined the ability of bufadienolides to penetrate the skin barrier using the Bronaugh Diffusion Cell Apparatus and Strat-M membrane. The study also assessed the ferric and molybdenum-reducing powers, as well as the radical scavenging capabilities of these plants juices using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) methods. The in vitro antihyaluronidase and antityrosinase activities and sun protection factor (SPF) were evaluated spectrophotometrically, indicating moderate capability to inhibit the skin enzymes, but low SPF protection for all analyzed juices. The semi-qualitative analysis demonstrated the presence of bufadienolides occurring in two juices from K. daigremontiana and K. pinnata, with the highest contents of 1,3,5-bersaldegenin-orthoacetate, bryophyllin-A/bryotoxin-C, bersaldegenin-acetate/bryophyllin-C, and diagremontianin. After passing through the skin model, no bufadienolide compounds were present in the subcutaneous filtrate. Antiradical and reduction assays revealed the antioxidant potential of K. blossfeldiana and K. pinnata. These results indicate that Kalanchoe juices have antiaging potential and appear safe for dermal applications. Full article

Molybdenum (Mo) is widely used as a micronutrient fertilizer to improve plant growth and soil quality. However, the interactions between cell wall biosynthesis and molybdenum have not been explored sufficiently. This study thoroughly investigated the regulatory effects of different concentrations of Mo on tobacco cell wall biosynthesis from physiological and metabolomic aspects. The results indicate that Mo treatment increased the Mo content of tobacco variety K326. Moreover, it significantly up-regulated the gene expression levels of molybdases (NR, AO, SO, XDH) and molybdate transporters in tobacco, whereby the gene expression levels of NR were upregulated by 28.48%, 52.51%, 173.05%, and 246.21%, respectively; and MOT1 and MOT2 were upregulated by 21.49/8.67%, 66.05/30.44%, 93.05/93.26%, and 166.11/114.29%, respectively. Additionally, Mo treatment regulated the synthesis of related enzymes, effectively promoted plant growth, and significantly increased biomass and dry matter accumulation, with the biomass in the leaves increasing significantly by 30.73%, 40.72%, 46.34%, and 12.88%, respectively. The FT-NIR spectroscopy results indicate that after Mo was applied to the soil, the quantity of C-O-C, -COOH, C-H, and N-H functional groups increased. Concurrently, the contents of cellulose, hemicellulose, lignin, protopectin, and soluble pectin in the leaves significantly increased, wherein the content of soluble pectin and hemicellulose increased significantly by 31.01/288.82%, 40.69/343.43%, 69.93/241.73%, and 196.88/223.26%, respectively. Furthermore, the cell walls thickened, increasing the ability of the plant to withstand disturbances. The metabolic network diagrams indicate that Mo regulated galactose metabolism, and arginine and proline acid biosynthesis. The contents of carbohydrates, spermidine, proline, quinic acid, IAA, flavonoids, and other substances were increased, increasing the levels of polysaccharides and pectin within the cell wall, controlling lignin production, and successfully enhancing resistance to abiotic stress. These results offer important perspectives for further investigations into the role of trace elements. Full article

Plant biotechnology creates opportunities for the cultivation of plants regardless of their natural habitats, which are often protected or difficult to access. Maintaining suspension cell cultures in bioreactors is an advanced part of biotechnological research that provides possibilities for obtaining plant tissue on a large scale. In this study, the suspension culture cultivation of a Chinese endemic plant, Schisandra henryi, in a stirred tank bioreactor was elaborated for the first time. The phytochemical profile of the tissue extracts was determined with UHPLC-MS/MS for the lignans (fifteen dibenzocyclooctadiene lignans, one aryltetralin lignan, and two neolignans) and UHPLC-DAD-ESI-MS³ for the phenolic compounds (procyanidins and their derivatives and catechin). The maximum total lignan content of 1289 µg/100 g DW was detected for the extracts from suspensions cultured in a bioreactor for over 10 days. For the phenolic compounds, catechin was the dominant compound (390.44 mg/100 g DW). The biological activity of the extracts was tested too. To determine antioxidant potential we used DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), Molybdenum reduction, and β-carotene bleaching tests. The inhibition activity of the S. henryi extract on the enzymes responsible for skin aging, hyaluronidase and tyrosinase, was assessed with spectrophotometry. The cytotoxic activity of the extracts was estimated on human ovarian SKOV-3, cervical HeLa, and gastric AGS cancer cells and non-cancer, normal fibroblasts by an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. The results showed the great potential of the obtained cell biomass extracts. The results of the antioxidant tests indicated their strong ability to reduce the level of free radicals, similarly to that of ascorbic acid, as well as the weak capacity to protect lipids from oxidation. Moreover, anticancer potential, particularly on the cervical and gastric cancer cells, was confirmed too. Full article

Physical activity induces modifications in the concentrations of trace mineral elements. However, studies exploring sex-related differences in manganese (Mn) and molybdenum (Mo) levels among athletes are scarce. Mn and Mo are essentials metals required for a variety of metabolic functions, including those involved in normal human development, the activation of certain metalloenzymes, energy metabolism, and immune system function. They are important cofactors for a variety of enzymes, including those involved in neurotransmitter synthesis and metabolism. The presence of molybdenum (Mo) is essential for several enzymes, including xanthine oxidase (XO), aldehyde oxidase, sulfite oxidase (SO), and the mitochondrial amidoxime reductase component (mARC). This study aimed to: (a) analyse changes in plasma, urine, erythrocyte, and platelet Mn and Mo concentrations throughout a competitive season in men’s and women’s football players, and (b) investigate sex-based discrepancies. A total of 46 football players (22 men: age; 20.62 ± 2.66 years; height; 1.76 ± 0.061 m; weight; 71.50 ± 5.93 kg, and 24 women: age; 23.21 ± 4.11 years; height; 1.65 ± 0.06 m; weight; 59.58 ± 7.17 kg) participated in this study. Three assessments were conducted throughout the competitive season. Data were collected on anthropometry, body composition, nutritional intake, physical fitness, female hormones, haematology, and the determination of Mn and Mo in different biological compartments. Regarding Mn, significant sex differences were observed in plasma, urine, and erythrocyte concentrations (p < 0.05). Moreover, significant variations were observed throughout the season in all analysed biological compartments (p < 0.05). Regarding Mo, significant sex differences were reported in plasma concentrations (p < 0.05). Similarly, there were variations throughout the season in all analysed biological compartments (p < 0.05). Plasma, urine, erythrocyte, and platelet Mn and Mo concentrations could change during a competitive season in football players. On the other hand, sex differences could exist in plasma, urine, and erythrocyte Mn concentrations in football players. Full article

Molybdenum (Mo) is an essential micronutrient across all kingdoms of life, where it functions as a key component of the active centers of molybdenum-dependent enzymes. For these enzymes to gain catalytic activity, Mo must be complexed with a pterin scaffold to form the molybdenum cofactor (Moco). The final step of Moco biosynthesis is catalyzed by the enzyme Mo-insertase. This review focuses on eukaryotic Mo-insertases, with an emphasis on those found in plants and mammals, which have been instrumental in advancing the understanding of Mo biochemistry. Additionally, a historical perspective is provided, tracing the discovery of Mo-insertase from the early 1960s to the detailed characterization of its reaction mechanism in 2021. This review also highlights key milestones in the study of Mo-insertase, including mutant characterization, gene cloning, structural elucidation at the atomic level, functional domain assignment, and the spatial organization of the enzyme within cellular protein networks. Full article

The arsRBC operon encodes a three-protein arsenic resistance system. ArsR regulates the transcription of the operon, while ArsB and ArsC are involved in exporting trivalent arsenic and reducing pentavalent arsenic, respectively. Previous research into Agrobacterium tumefaciens 5A has demonstrated that ArsR has regulatory control over a wide range of metal-related proteins and metabolic pathways. We hypothesized that ArsR has broad regulatory control in other Gram-negative bacteria and set out to test this. Here, we use differential proteomics to investigate changes caused by the presence of the arsR gene in human microbiome-relevant Escherichia coli during arsenite (As^III) exposure. We show that ArsR has broad-ranging impacts such as the expression of TCA cycle enzymes during As^III stress. Additionally, we found that the Isc [Fe-S] cluster and molybdenum cofactor assembly proteins are upregulated regardless of the presence of ArsR under these same conditions. An important finding from this differential proteomics analysis was the identification of response mechanisms that were strain-, ArsR-, and arsenic-specific, providing new clarity to this complex regulon. Given the widespread occurrence of the arsRBC operon, these findings should have broad applicability across microbial genera, including sensitive environments such as the human gastrointestinal tract. Full article