Inhibitory Effect Of Metal Ions Research Articles

Synergistic bimetallic nanozymes of Ni/ZIF-8 and Cu/ZIF-8 as carbonic anhydrase mimics

The remarkable diversity of metal nodes and ligands, coupled with the extensive array of connection modes, enables the precise design and assembly of metal-organic frameworks (MOFs), which have garnered significant attention in the field of nanozyme. In this study, the synthesis of zeolite imidazole framework materials (ZIFs) with varying Zn2+ and Ni2+ or Cu2+ concentrations were investigated and regulated by methanol, aiming to mimic the CO2 hydration activity of carbonic anhydrase (CA). The materials were comprehensively characterized using TEM, XRD, FTIR, UV-Vis DRS, XPS, and subsequently the catalytic performance of the materials was assessed. The results demonstrated that the structural characteristics of bimetallic Ni/ZIF-8 and Cu/ZIF-8 were influenced by varying concentrations of metal ions. Notably, ZIF-8 doped with lower metal content exhibited enhanced stability, while a precursor containing nickel and copper ions exceeding 50% hindered the formation of the desired ZIFs, resulting in an unstable cluster structure. However, methanol can counteract the inhibitory effect of metal ions on the structure. The bimetallic synergies of doped metals in ZIFs CA mimics can simultaneously expedite both two rate-limiting steps in the CO2 hydration process. The esterase activity of ZIF-8 doped with a small quantity of Ni2+ or Cu2+ can be achieved at a level comparable to that of human carbonic anhydrase (hCA II) at 80 °C, along with remarkable catalytic performance and hydrothermal stability. Specifically, Cu66%/ZIF-8 exhibited an activity of 0.31 U·mg−1 at 25 °C, which was 2.31 times higher than that of ZIF-8, moreover, the esterase activity at 80 °C was approximately 2.21 times greater than that of ZIF-8 under the same condition. While the relative activity of Ni50%/ZIF-8 and Cu50%/ZIF-8 still exceeding 50% even after five repeated utilization cycles. The bimetallic Ni/ZIF-8 and Cu/ZIF-8 can be easily synthesized using a simple method, resulting in enhanced catalytic activity. Therefore, it holds great potential for future applications in CO2 capture.

Immobilization of Camel Liver Catalase on Nanosilver-Coated Cotton Fabric

Nanoparticles have the advantage of a superior surface area to volume ratio, and thus such materials are useful for enzyme immobilization. A silver nanoparticle coated cotton fabric (AgNp-CF) is used to immobilize camel liver catalase in the present work. The effect of loading levels of AgNp inside cotton fabrics on the immobilization of catalase was investigated. The results revealed that a 6 mL loading level of AgNp precursor (silver nitrate, 2 mM) at pH 8 showed the maximum immobilization efficiency (76%). The morphological properties of the cotton fabric (CF), AgNp-CF and AgNp-CF-catalase were characterized by SEM. The reusability of the immobilized enzyme was tested over ten reuses to show a 67% retained function of its initial activity. Compared with the soluble enzyme’s working pH (6.5), a rather broader working pH (6.5–7.0) was observed for the immobilized catalase. Additionally, the optimum working temperature increased from 30 for the soluble enzyme to 40 °C for the immobilized one, indicating thermal stability. The free and immobilized catalase enzyme’s Km values were 22.5 and 25 mM H2O2, respectively, reflecting the enzyme’s effective properties. The inhibitory effect of metal ions on the enzyme activity was higher toward soluble catalase than the immobilized catalase. This work has developed a method for immobilizing catalase to be useful for several applications.

Purification of Glutathione Reductase From Some Tissues of Capoeta umbla and the Inhibitory Effects of Some Metal Ions on Enzyme Activity

The aim of this study was to determine the in vitro inhibitory effects of some metal ions (silver ion (Ag+), cadmium ion (Cd2+), cobalt ion (Co2+), copper ion (Cu2+), nickel ion (Ni2+), lead ion (Pb2+) and zinc ion (Zn2+)) on glutathione reductase (GR) enzyme activities that purified from the gill, kidney and liver tissues of Capoeta umbla. For this purpose, the enzyme was purified from the gill, kidney and liver of C. umbla freshwater fish using ammonium sulfate precipitation and affinity column chromatography methods using 2′,5′-ADP Sepharose 4B. Within this study, the GR enzyme was purified for the first time from the tissues of C. umbla. Enzyme purity and molecular weight were determined using the sodium dodecyl sulfate polyacrylamide gel electrophoresis method. In addition, the inhibitory effects of different metal ions (Ag+, Cd2+, Co2+, Cu2+, Ni2+, Pb2+ and Zn2+) on GR enzyme activities of the gill, kidney and liver tissue of C. umbla were investigated under in vitro conditions. The metal ion concentrations inhibiting 50% of enzyme activity (IC50) were obtained by plotting activity percentage versus [I] figures. Finally, the dissociation constants of the enzyme inhibitor complex (Ki), and the inhibition types, were calculated from Lineweaver–Burk plots. In vitro inhibition rank order was determined as Ag+>Co2+>Pb2+>Zn2+>Cu2+ for C. umbla gill GR; Ag+>Pb2+>Co2+> Ni2+>Zn2+ for C. umbla liver GR; Ag+>Cu2+>Co2+>Pb2+>Ni2+ for C. umbla kidney GR. From these results, we showed that Ag+ metal ion is the most potent inhibitor of GR enzyme on gill, liver and kidney tissues. Our results also demonstrate that these metals might be dangerous at low micromolar concentrations for C. umbla GR enzyme.

Effect of Cu2+ and Cd2+ on the growth and sulfidogenic activity of sulfate-reducing bacteria under using aromatic hydrocarbons

Purification of the aquatic environment from substances of organic and inorganic matter is an urgent problem nowadays. Falling into the water of insufficiently treated effluents significantly impairs water quality and the condition of water bodies in general. Aromatic compounds, in particular toluene and xylene, are quite common pollutants in the aquatic environment. In addition to compounds of organic nature, wastewater contains many inorganic substances and heavy metal ions. Among the common methods of detoxification of the environment, biological ones play a leading role, as they are cost-effective and environmentally safe. One of the promising methods of purification is the usage of microorganisms, in particular sulfate-reducing bacteria. The influence of heavy metal ions on the accumulation of biomass and hydrogen sulfide by Desulfotomaculum sp. AR1 and D. desulfuricans Ya-11 bacteria during the growth in a medium with toluene and xylene is studied. The ability of sulfate-reducing bacteria Desulfotomaculum sp. AR1 and D. desulfuricans Ya-11 to grow with the simultaneous presence of aromatic compounds and heavy metal ions into the environment indicates their high potential in the usage to purify the aquatic environment from these contaminants. The inhibitory effect of metal ions on the process of reduction of sulfate ions by the studied bacteria, and, as a consequence, the accumulation of less toxic hydrogen sulfide, is shown. The influence of the source of carbon (sodium lactate/xylene/toluene) and heavy metal ions on the growth of bacteria Desulfotomaculum sp. AR1 and D. desulfuricans Ya-11 is analysed. It is shown that the accumulation of biomass by bacteria Desulfotomaculum sp. AR1 and D. desulfuricans Ya-11 are affected by both the nature of the electron donor and the presence of Cu2+ and/or Cd2+ ions in the medium. Penetrating into living cells, heavy metal ions disrupt their vital functions, but heavy metals are toxic only in the form of ions, but if they are translated into a bound form, they lose their toxic properties. The ability of the studied bacteria to precipitate Cu2+ and Cd2+ ions in the form of insoluble metal sulfides was revealed. Thus, the content of hydrogen sulfide in the aqueous medium can be adjusted, and in turn, it can be purified from heavy metal ions. According to the obtained results, sulfate-reducing bacteria Desulfotomaculum sp. AR1 and D. desulfuricans Ya-11 can be considered as promising in the development of methods for purification of the aquatic environment from heavy metal ions, in particular Cu2+ and Cd2+

Inhibitory effects of metal ions on reductive dechlorination of polychlorinated biphenyls and perchloroethene in distinct organohalide-respiring bacteria

Bioremediation of sites co-contaminated with organohalides and metal pollutants may have unsatisfactory performance, since metal ions can potentially inhibit organohalide respiration. To understand the detailed impact of metals on organohalide respiration, we tested the effects of four metal ions (i.e., Cu2+, Cd2+, Cr3+ and Pb2+), as well as their mixtures, on reductive dechlorination of perchloroethene (PCE) and polychlorinated biphenyls (PCBs) in three different cultures, including a pure culture of Dehalococcoides mccartyi CG1, a Dehalococcoides-containing microcosm and a Dehalococcoides-Geobacter coculture. Results showed that the inhibitive impact on organohalide respiration depended on both the type and concentration of metal ions. Interestingly, the metal ions might indirectly inhibit organohalide respiration through affecting non-dechlorinating populations in the Dehalococcoides-containing microcosm. Nonetheless, compared to the CG1 pure culture, the Dehalococcoides-containing microcosm had higher tolerance to the individual metal ions. In addition, no synergistic inhibition was observed for reductive dechlorination of PCE and PCBs in cultures amended with metal ion mixtures. These results provide insights into the impact of metal ions on organohalide respiration, which may be helpful for future in situ bioremediation of organohalide-metal co-contaminated sites.

Y3 +, La3 +, and some bivalent metals inhibited the opening of the Tl+-induced permeability transition pore in Ca2 +-loaded rat liver mitochondria

We showed earlier that diminution of 2,4-dinitrophenol (DNP)-stimulated respiration and increase of both mitochondrial swelling and electrochemical potential (ΔΨmito) dissipation in medium containing TlNO3 and KNO3 were caused by opening of Tl+-induced mitochondrial permeability transition pore (MPTP) in the inner membrane of Ca2+-loaded rat liver mitochondria. The MPTP opening was studied in the presence of bivalent metal ions (Sr2+, Ba2+, Mn2+, Co2+ and Ni2+), trivalent metal ions (Y3+ and La3+), and ruthenium red. We found that these metal ions (except Ba2+ and Co2+) as well as ruthenium red inhibited to the MPTP opening that manifested in preventing both diminution of the DNP-stimulated respiration and increase of the swelling and of the ΔΨmito dissipation in medium containing TlNO3, KNO3, and Ca2+. Inhibition of the MPTP opening by Sr2+ and Mn2+ is suggested because of their interaction with high affinity Ca2+ sites, facing the matrix side and participating in the MPTP opening. The inhibitory effects of metal ions (Y3+, La3+, and Ni2+), and ruthenium red are accordingly discussed in regard to competitive and noncompetitive inhibition of the mitochondrial Ca2+-uniporter. High concentrations (50μM) of Y3+ and La3+ favored of MPTP opening in the inner membrane of rat liver mitochondria in Ca2+ free medium containing TlNO3. The latter MPTP opening was markedly eliminated by MPTP inhibitors (cyclosporine A and ADP).

Inhibitory effect of metal ions on the poly-phosphate release from sewage sludge during thermal treatment

The purpose of this study was aimed at identifying the influence of metal cations such as Mg2+, Ca2+, Al3+ and Fe3+ on poly-phosphate (poly-P) and total phosphate (T-P) release from sewage sludge collected from wastewater treatment plant during thermal treatment at 70°C for 80 min. With the addition of chelating reagent such as EDTA, release of poly-P and T-P was improved obviously during thermal treatment. Inhibitory effect of metal cations on phosphorus release was apparent by adding metal cations into sludge sample. Most of Ca, Al and Fe inside of cell could be released into the supernatant, but captured in extracellular polymeric substance (EPS); oppositely, large quantity of Mg could be released into the supernatant directly and not concentrated in EPS. Performance of sewage sludge on phosphorus release in summer and winter was different; different precipitation and temperature possibly result in this phenomenon.

Effects of metal ions on THMs and HAAs formation during tannic acid chlorination

The present study was implemented to examine THM and HAA formation from the chlorination of tannic acid (TA) in the presence of common metal ions (e.g., Mg2+, Fe2+, Mn2+, Cu2+, Al3+) typically found in water sources. The inhibition efficiency of THM formation followed the order Mg2+<Cu2+<Fe2+<Mn2+<Al3+ and the effect of HAA enhancement followed the order Mg2+<Mn2+<Cu2+<Al3+<Fe2+. Similar to the case of single metal ion, the presence of multiple metal ions exerted analogous influence on the THM and HAA formation but without synergistic enhancement or inhibition. The investigation of nuclear magnetic resonance (NMR) and Electron Paramagnetic Resonance (EPR) spectroscopy indicated that the inhibitory effect of metal ions on THM formation was proportional to the changes in electron densities of active sites of tannic acid while the promoting effect of metal ions on HAA formation was more related to the generation of hydroxyl radical caused by the presence of metal ions. This study suggests that two different mechanisms could be involved in the effects of metal ions on THM and HAA formation from TA chlorination.

Purification and characterization of glutathione S-transferase from turkey liver and inhibition effects of some metal ions on enzyme activity

The glutathione S-transferases (EC 2.5.1.18) were purified and characterized from turkey liver for the first time. The enzyme was purified 252.7-fold with a yield of 45%, with a specific activity of 164.31U/mg from turkey liver. The purity of the enzyme was determined by SDS-PAGE and showed two bands nearly 26kDa and 24kDa on the gel. The native molecular mass of the enzyme was found to be approximately 53kDa by Sephadex G-100 gel filtration chromatography. Optimal pH, stable pH, optimal temperature, optimum ionic strength, Km and Vmax values for GSH and CDNB were also determined for the enzyme as 7.3, 8.5, 50°C, 600mM, 0.154mM, 0.380mM, 1.803EU/ml, and 2.125EU/ml, respectively. Additionally, inhibitory effects of metal ions (Cu2+, Hg2+, Fe2+, Zn2+, Ag+, Mg2+, Ni2+, and Mn2+) were examined the enzyme's activity in vitro by performing Lineweaver–Burk graphs and plotting activity% vs., respectively.

Purification of glutathione S-transferase isoenzymes from tumour and nontumour human stomach and inhibitory effects of some heavy metals on enzymes activities

In this study, glutathione S-transferase (GST) enzyme was purified from nontumour and tumour human gastric tissue and in vitro effects of heavy metals on the enzyme were examined. GST was purified 3089 fold with a specific activity of 20 U/mg and a yield of 78% from gastric tumour tissue; and 1185 fold with a specific activity of 5.69 U/mg and a yield of 50% from nontumour tissue by using glutathione−agarose affinity column, respectively. Enzyme purity was verified by SDS-PAGE and subunit molecular mass was calculated around 26 kDa. The molecular weight of the enzyme was calculated as 52 kDa by using Sephadex G-75 gel filtration column. Then, inhibitory effects of metal ions on the enzymes were investigated. Mg2+ and Cd2+ had inhibitory effect on the enzymes activities. Other kinetic properties of the enzymes were also determined.

Zn(II)‐ and Cu(II)‐induced non‐fibrillar aggregates of amyloid‐β (1–42) peptide are transformed to amyloid fibrils, both spontaneously and under the influence of metal chelators

Aggregation of amyloid-beta (Abeta) peptides is a central phenomenon in Alzheimer's disease. Zn(II) and Cu(II) have profound effects on Abeta aggregation; however, their impact on amyloidogenesis is unclear. Here we show that Zn(II) and Cu(II) inhibit Abeta(42) fibrillization and initiate formation of non-fibrillar Abeta(42) aggregates, and that the inhibitory effect of Zn(II) (IC(50) = 1.8 micromol/L) is three times stronger than that of Cu(II). Medium and high-affinity metal chelators including metallothioneins prevented metal-induced Abeta(42) aggregation. Moreover, their addition to preformed aggregates initiated fast Abeta(42) fibrillization. Upon prolonged incubation the metal-induced aggregates also transformed spontaneously into fibrils, that appear to represent the most stable state of Abeta(42). H13A and H14A mutations in Abeta(42) reduced the inhibitory effect of metal ions, whereas an H6A mutation had no significant impact. We suggest that metal binding by H13 and H14 prevents the formation of a cross-beta core structure within region 10-23 of the amyloid fibril. Cu(II)-Abeta(42) aggregates were neurotoxic to neurons in vitro only in the presence of ascorbate, whereas monomers and Zn(II)-Abeta(42) aggregates were non-toxic. Disturbed metal homeostasis in the vicinity of zinc-enriched neurons might pre-dispose formation of metal-induced Abeta aggregates, subsequent fibrillization of which can lead to amyloid formation. The molecular background underlying metal-chelating therapies for Alzheimer's disease is discussed in this light.

Purification and characterization of glutathione reductase from rainbow trout ( Oncorhynchus mykiss) liver and inhibition effects of metal ions on enzyme activity

Glutathione reductase (E C: 1.8.1.7; GR) was purified from rainbow trout ( Oncorhynchus mykiss) liver, and some characteristics of the enzyme were investigated. The purification procedure consisted of four steps: preparation of homogenate, ammonium sulfate fractionation, affinity chromatography on 2′,5′-ADP Sepharose-4B and gel filtration chromatography on Sephadex G-200. The enzyme, with a specific activity of 27.45 U/mg protein, was purified 1,654-fold with a yield of 41%. Optimal pH, stable pH, optimal temperature, optimum ionic strength, molecular mass, K M and V max values for GSSG and NADPH were also determined for the enzyme. In addition, K i values and inhibition types were determined for GSH and NADP +. Additionally, inhibitory effects of metal ions (Cd + 2 , Cu + 2 , Pb + 2 , Hg + 2 , Fe + 3 and Al + 3 ) on glutathione reductase were investigated. K i constants and IC 50 values for metal ions were determined by Lineweaver–Burk graphs and plotting activity % vs. [I], respectively. IC 50 values of Cd + 2 ,Cu + 2 , Pb + 2 , Hg + 2 , Fe + 3 and Al + 3 were 0.0655, 0.082, 0.122, 0.509, 0.797 and 0.804 mM, and the K i constants for Cd + 2 and Cu + 2 were 0.104 ± 0.001, 0.117 ± 0.001, respectively.

Development of a high-throughput purification method and a continuous assay system for chlorophyllase

In the degradation of chlorophyll, chlorophyllase catalyzes the initial hydrolysis of the phytol moiety from the pigment. Since chlorophyll degradation is a defining feature of plant senescence, compounds inhibiting chlorophyllase activity may delay senescence, thereby improving shelf life and appearance of plant products. Here we describe the development of a 96-well plate-based purification and assay system for measuring chlorophyllase activity. Integrated lysis and immobilized metal affinity chromatography plates were used for purifying recombinant hexahistidine-tagged Triticum aestivum (wheat) chlorophyllase from Escherichia coli. Chlorophyllase assays using chlorophyll as a substrate showed that the immobilized fusion protein displayed kinetic parameters similar to those of recombinant enzyme purified by affinity chromatography; however, the need to extract reaction products from a multiwell plate limits the value of this assay for high-throughput screening applications. Replacing chlorophyll with p-nitrophenyl-ester substrates eliminates the extraction step and allows for continuous measurement of chlorophyllase activity in a multiwell plate format. Determination of steady state kinetic constants, pH rate profile, the inhibitory effects of metal ions and esterase inhibitors, and the effect of functional group-modifying reagents validated the utility of the plate-based system. The combined purification and assay system provides a convenient and rapid method for the assessment of chlorophyllase activity.

A Catalytic Method for Determining Cadmium(II), Nickel(II), and Zinc(II) Inhibitor Metals

The inhibitory effect of Cd(II), Ni(II), and Zn(II) on the oxidation of 3,3′,5,5′ -tetramethylbenzidine with periodate was detected. The optimum reaction conditions were found, and the procedures were developed for determining 1 × 10−2 to 10 μg/mL Cd(II), Ni(II), and Zn(II) in solution. The indicator reaction was performed on a number of supports. The maximum inhibitory effect was observed on silica gel-based plates for TLC. Procedures for determining 6 × 10−3 to 0.4 μg of these metals were developed. Silica gel plates with the immobilized reagent for cadmium (bromobenzothiazo) were used to preconcentrate cadmium. A selective test procedure was developed for determining 1 × 10−4 −3 × 10−3 μg/mL cadmium with the visual detection of the process rate. Upon the introduction of dimethylglyoxime into the indicator reaction, the inhibitory effect of nickel changed to its promoting effect and the detection limit for nickel was lowered. A procedure was developed for determining 3 × 10−4 −3 × 10−3 μg/mL nickel in solution and 7 × 10−3−4 × 10−1 μg nickel on the surface of Sorbfil plates. An assumption was made about the reasons for the inhibitory effect of metal ions on the oxidation of aryl diamines with periodate.

Synergetic inhibition of metal ions and genistein on α-glucosidase

Inhibition of metal ions and synergetic inhibition of metal ions/genistein on α-glucosidase activity has been investigated. We have examined the inhibitory effect of Cu 2+, Ni 2+, Mg 2+, Fe 2+, Hg 2+, Zn 2+, Ca 2+, Pb 2+, Ag +, V 5+, V 4+ and Mn 2+ ions. The results show that the nature of the inhibition was reversible, slow-binding, non-competitive, and the K i values of some ions such as Cu 2+, Ni 2+ and Zn 2+ range from 10 −5 to 10 −6 M. Moreover, synergetic inhibitory effect of metal ions and genistein on α-glucosidase were studied with kinetics method. It is concluded that the inhibitory effect was much greater when both of them were added to the reactant solution simultaneously than that they were added, respectively, which suggests that the inhibitors seem to bind to the different sites of α-glucosidase at the same time. Furthermore, the mechanism of the synergetic inhibition was examined by spectrophotometry.

Utilisation of fruits waste for citric acid production by solid state fermentation

A solid state fermentation method was used to utilise pineapple, mixed fruit and maosmi waste as substrates for citric acid production using Aspergillus niger DS 1. Experiments were carried out in the presence and absence of methanol at different moisture levels. In the absence of methanol the maximum citric acid was obtained at 60% moisture level whereas in the presence of methanol the maximum citric acid was obtained at 70% moisture level. The stimulating effect of methanol was less at lower moisture level. The inhibitory effect of metal ions was also not observed and maximum citric acid yield of 51.4, 46.5 and 50% (based on sugar consumed) was obtained from pineapple, mixed fruit and maosmi residues, respectively.

Comparison of Characteristics of Acid Phosphatases Secreted from Roots of Lupin and Tomato

Abstract In this study we purified both acid phosphatases (Apase) secreted from tomato and lupin roots, and compared the properties of these two enzymes. The secretory Apases from tomato and lupin showed the following similar properties. 1) Both enzymes were homodimers consisting of two identical subunits, each with a molecular weight of approximately 68 kilodaltons (kD) in tomato and 72 kD in lupin. 2) The enzymes were stable in the pH range of 4–9. 3) The enzymes showed an optimum temperature of 37–40°C for their activity and were stable at temperatures below 60°C. 4) The enzymes exhibited a comparable affinity for p-nitrophenyl phosphate (the apparent K m values were 2.7–3.0 × 10-5 M). On the other hand, there were some slight differences in the isoelectric point, optimum pH, specific activity, substrate specificity, and inhibitory effect of metal ions between the two enzymes. Therefore, it was considered that the most important difference in the root ability of the two plants to hydrolyze organic phos...

Mechanism of inhibitory effect of metal ions on induction of the adaptive response. II

Mechanism of inhibitory effect of metal ions on induction of the adaptive response. II

Influence of trace metal ions on matrix vesicle calcification

Since the proposal by Roivison that alkaline phosphatase (ALP) has a role in calcification [ 11, and the later demonstration that its activity was dependent on the presence of Zn2” [2], a role for trace metals in biological mineralization has been indicated. Nutritional studies in poultry in the 1950’s and 60’s showed that dietary deficiencies of Mn2+, Cu2+, or Zn*+ resulted in severe skeletal disorders [3]. Subsequently, it was found that excessive amounts of these metal ions could a!so be harmful to the skeletal system. In vitro studies indicated an inhibitory effect of metal ions on endochondral mineralization [4]. In more recent years, toxic metal ions such as Cd2+ and A13+ have been identified as etiological agents in a number of bone diseases [S-6]. Prior to the discovery of matrix vesicles (MV) by Anderson [7] and Bonucci [8], histochemical studies showed a colocalization of Zn2+ and Sudanophilic material in the hypertrophic region of the epiphyseal growth plate [9]. The discovery of MV readily explained the Sudanophilic reaction, however, it has been only recently that these structures were found to contain substantial amounts of Zn2+ [lo]. Since our discovery of the importance of Zn*+ in MV mineralization, we have investigated a number of aspects of MV function which may be affected by the presence of trace metal ions, including: 1) MV enzyme activities; 2) mineral ion transport; and 3) mineral nucleation, maturation, and growth.

Mechanism for inhibitory effect of metal ions on induction of the adaptive response

Mechanism for inhibitory effect of metal ions on induction of the adaptive response