scholarly journals Kinetic characterization of enzyme forms involved in metal ion activation and inhibition of myo-inositol monophosphatase

1995 ◽  
Vol 307 (2) ◽  
pp. 585-593 ◽  
Author(s):  
F Strasser ◽  
P D Pelton ◽  
A J Ganzhorn
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Catalytic Mechanism ◽  
Inositol Monophosphatase ◽  
Inositol 1 ◽  
Enzyme Substrate ◽  
Nitrophenyl Phosphate ◽  
Preferential Binding ◽  
Sugar Phosphates ◽  
High Concentrations

Activation and inhibition of recombinant bovine myo-inositol monophosphatase by metal ions was studied with two substrates, D,L-inositol 1-phosphate and 4-nitrophenyl phosphate. Mg2+ and Co2+ are essential activators of both reactions. At high concentrations, they inhibit hydrolysis of inositol 1-phosphate, but not 4-nitrophenyl phosphate. Mg2+ is highly selective for inositol 1-phosphate (kcat. = 26 s-1) compared with the aromatic substrate (kcat. = 1 s-1), and follows sigmoid activation kinetics in both cases. Co2+ catalyses the two reactions at similar rates (kcat. = 4 s-1), but shows sigmoid activation only with the natural substrate. Li+ and Ca2+ are uncompetitive inhibitors with respect to inositol 1-phosphate, but non-competitive with respect to 4-nitrophenyl phosphate. Both metal ions are competitive inhibitors with respect to Mg2+ with 4-nitrophenyl phosphate as the substrate. With inositol 1-phosphate, Ca2+ is competitive and Li+ non-competitive with respect to Mg2+. Multiple inhibition studies indicate that Li+ and Pi can bind simultaneously, whereas no such complex was detected with Ca2+ and Pi. Several sugar phosphates were also characterized as substrates of myo-inositol monophosphatase. D-Ribose 5-phosphate is slowly hydrolysed (kcat. = 3 s-1), but inhibition by Li+ is very efficient (Ki = 0.15 mM), non-competitive with respect to the substrate and competitive with respect to Mg2+. Depending on the nature of the substrate, Li+ inhibits by preferential binding to free enzyme (E), the enzyme-substrate (E.S) or the enzyme-phosphate (E.Pi) complex. Ca2+, on the other hand, inhibits by binding to E and E.S, in competition with Mg2+. The results are discussed in terms of a catalytic mechanism involving two metal ions.

Efficient Preconcentration of Cu2+, Zn2+ and Fe3+ with an Agarose-Schiff Base Sorbent

2007 ◽  
Vol 72 (7) ◽  
pp. 908-916 ◽  
Author(s):  
Payman Hashemi ◽  
Hatam Hassanvand ◽  
Hossain Naeimi
Keyword(s):  
Schiff Base ◽  
Metal Ions ◽  
Metal Ion ◽  
Good Accuracy ◽  
Kinetic Studies ◽  
Sample Volume ◽  
Effects Of Ph ◽  
Glass Column ◽  
High Concentrations ◽  
Ph Range

Sorption and preconcentration of Cu2+, Zn2+ and Fe3+ on a salen-type Schiff base, 2,2'- [ethane-1,2-diylbis(nitrilomethylidyne)]bis(2-methylphenol), chemically immobilized on a highly crosslinked agarose support, were studied. Kinetic studies showed higher sorption rates of Cu2+ and Fe3+ in comparison with Zn2+. Half-times (t1/2) of 31, 106 and 58 s were obtained for sorption of Cu2+, Zn2+ and Fe3+ by the sorbent, respectively. Effects of pH, eluent concentration and volume, ionic strength, buffer concentration, sample volume and interferences on the recovery of the metal ions were investigated. A 5-ml portion of 0.4 M HCl solution was sufficient for quantitative elution of the metal ions from 0.5 ml of the sorbent packed in a 6.5 mm i.d. glass column. Quantitative recoveries were obtained in a pH range 5.5-6.5 for all the analytes. The volumes to be concentrated exceeding 500 ml, ionic strengths as high as 0.5 mol l-1, and acetate buffer concentrations up to 0.3 mol l-1 for Zn2+ and 0.4 mol l-1 for Cu2+ and Fe3+ did not have any significant effect on the recoveries. The system tolerated relatively high concentrations of diverse ions. Preconcentration factors up to 100 and detection limits of 0.31, 0.16 and 1.73 μg l-1 were obtained for Cu2+, Zn2+ and Fe3+, respectively, for their determination by a flame AAS instrument. The method was successfully applied to the metal ion determinations in several river water samples with good accuracy.

scholarly journals Elucidating the role of metal ions in carbonic anhydrase catalysis

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Jin Kyun Kim ◽  
Cheol Lee ◽  
Seon Woo Lim ◽  
Aniruddha Adhikari ◽  
Jacob T. Andring ◽  
...  
Keyword(s):  
Carbonic Anhydrase ◽  
Metal Ions ◽  
Metal Ion ◽  
Catalytic Mechanism ◽  
Chemical Properties ◽  
Water Network ◽  
Native Metal ◽  
Trigonal Bipyramidal ◽  
Electrostatic Effect

Abstract Why metalloenzymes often show dramatic changes in their catalytic activity when subjected to chemically similar but non-native metal substitutions is a long-standing puzzle. Here, we report on the catalytic roles of metal ions in a model metalloenzyme system, human carbonic anhydrase II (CA II). Through a comparative study on the intermediate states of the zinc-bound native CA II and non-native metal-substituted CA IIs, we demonstrate that the characteristic metal ion coordination geometries (tetrahedral for Zn2+, tetrahedral to octahedral conversion for Co2+, octahedral for Ni2+, and trigonal bipyramidal for Cu2+) directly modulate the catalytic efficacy. In addition, we reveal that the metal ions have a long-range (~10 Å) electrostatic effect on restructuring water network in the active site. Our study provides evidence that the metal ions in metalloenzymes have a crucial impact on the catalytic mechanism beyond their primary chemical properties.

scholarly journals Trace Metal Detection in Aqueous Reservoirs Using Stilbene Intercalated Layered Rare-Earth Hydroxide Tablets

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Solomon Omwoma
Keyword(s):  
Trace Metal ◽  
Metal Ions ◽  
Metal Ion ◽  
Aqueous Media ◽  
Mitigation Measures ◽  
Metal Ion Analysis ◽  
Gradual Process ◽  
Metal Detection ◽  
Trace Metal Detection ◽  
High Concentrations

Contamination of aquatic reservoirs with metal ions is a slow gradual process that is not easy to detect. Consequences of the metal ions, especially the ones with high atomic numbers (heavy metals) at high concentrations, are severe and irreversible in aquatic reservoirs. As such, early detection mechanisms, especially at trace concentration, are essential for mitigation measures. In this work, a new, robust, and effective tool for trace metal detection and monitoring in aqueous solutions has been developed. Tablets (1 mm thick and similar to medicinal tablets) were manufactured from a powder comprising stilbene intercalated into gallery spaces of lanthanide-containing layered double hydroxides. The tablets were placed in a water column having different concentrations of Pb2+ and Cu2+ ions, and the water was allowed to flow for 45 minutes at a flow rate of 100 ml/s. Thereafter, the tablets were dried and made to powder, and their phosphorescence was measured. The gradual stilbene phosphorescence turnoff in the tablets from various concentrations of metal ions was correlated with sorption amounts. The tablets were able to detect effectively metal ions (up to Pb2+ 1.0 mmol/L and Cu2+ 5.0 mmol/L) in the aqueous media. As such, the concentrations of Pb2+ and Cu2+ ions at trace levels were determined in the test solutions. This method provides a real-time metal ion analysis and does not involve sampling of water samples for analysis in the laboratory.

Structural elucidation of a dual-activity PAP phosphatase-1 fromEntamoeba histolyticacapable of hydrolysing both 3′-phosphoadenosine 5′-phosphate and inositol 1,4-bisphosphate

2014 ◽  
Vol 70 (7) ◽  
pp. 2019-2031 ◽  
Author(s):  
Khaja Faisal Tarique ◽  
Syed Arif Abdul Rehman ◽  
S. Gourinath
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Genomic Analysis ◽  
Inositol Polyphosphate ◽  
Inositol Monophosphatase ◽  
Native Form ◽  
Catalytic Loop ◽  
Important Regulator ◽  
Living Organisms ◽  
Toxic Byproduct

The enzyme 3′-phosphoadenosine 5′-phosphatase-1 (PAP phosphatase-1) is a member of the Li+-sensitive Mg2+-dependent phosphatase superfamily, or inositol monophosphatase (IMPase) superfamily, and is an important regulator of the sulfate-activation pathway in all living organisms. Inhibition of this enzyme leads to accumulation of the toxic byproduct 3′-phosphoadenosine 5′-phosphate (PAP), which could be lethal to the organism. Genomic analysis ofEntamoeba histolyticasuggests the presence of two isoforms of PAP phosphatase. The PAP phosphatase-1 isoform of this organism is shown to be active over wide ranges of pH and temperature. Interestingly, this enzyme is inhibited by submillimolar concentrations of Li+, while being insensitive to Na+. Interestingly, the enzyme showed activity towards both PAP and inositol 1,4-bisphosphate and behaved as an inositol polyphosphate 1-phosphatase. Crystal structures of this enzyme in its native form and in complex with adenosine 5′-monophosphate have been determined to 2.1 and 2.6 Å resolution, respectively. The PAP phosphatase-1 structure is divided into two domains, namely α+β and α/β, and the substrate and metal ions bind between them. This is a first structure of any PAP phosphatase to be determined from a human parasitic protozoan. This enzyme appears to function using a mechanism involving three-metal-ion assisted catalysis. Comparison with other structures indicates that the sensitivity to alkali-metal ions may depend on the orientation of a specific catalytic loop.

scholarly journals Kinetics of alkaline phosphatase from pig kidney. Mechanism of activation by magnesium ions

1974 ◽  
Vol 141 (1) ◽  
pp. 257-263 ◽  
Author(s):  
Jan Ahlers
Keyword(s):  
Alkaline Phosphatase ◽  
Metal Ions ◽  
Metal Ion ◽  
Ion Concentration ◽  
British Library ◽  
Kinetic Measurements ◽  
Pig Kidney ◽  
Enzyme Substrate ◽  
Lending Library ◽  
Model Scheme

The mechanism of activation of alkaline phosphatase (EC 3.1.3.1) from pig kidney by Mg2+ ions was investigated with the aid of kinetic measurements. Mg2+ ions are essential for enzyme activity. The following model (Scheme 1 of the text) for the reaction of enzyme, substrate and Mg2+ ions was derived: [Formula: see text] The binding of the substrate to the enzyme is independent of the binding of the activator, and vice versa. Mg2+ must therefore play a part in the substrate decomposition. It is not possible to determine whether the Mg2+ ions are involved directly in the catalytic process, or whether they act as regulatory effectors. Because of the strong affinity existing between the alkaline phosphatase and Mg2+, it is necessary to adjust the metal-ion concentration with the aid of a metal buffer. In the Appendix the necessary equations are derived for calculating the concentration of free metal ions in a system with several different metal ions. A FORTRAN IV program for solving these equations and for graphic presentation of the results has been deposited as Supplementary Publication SUP 50030 at the British Library (Lending Division) (formerly the National Lending Library for Science and Technology), Boston Spa, Yorks. LS 23 7 BQ, U.K., from whom copies may be obtained on the terms indicated in Biochem. J. (1973), 131, 5.

scholarly journals Comparison of Inflammatory Effects in THP-1 Monocytes and Macrophages after Exposure to Metal Ions

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1150
Author(s):  
Henrike Loeffler ◽  
Anika Jonitz-Heincke ◽  
Kirsten Peters ◽  
Brigitte Mueller-Hilke ◽  
Tomas Fiedler ◽  
...  
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Cell Types ◽  
Cell Number ◽  
Corrosion Products ◽  
Proinflammatory Mediators ◽  
Csf Proteins ◽  
Monocytes And Macrophages ◽  
High Concentrations ◽  
Negative Controls

Monocytes and macrophages are the first barrier of the innate immune system, which interact with abrasion and corrosion products, leading to the release of proinflammatory mediators and free reactive molecules. The aim of this study was to understand inflammation-relevant changes in monocytes and macrophages after exposure to corrosion products. To do this, the THP-1 cell line was used to analyze the effects of metal ions simultaneously in monocytes and differentiated macrophages. Cells were stimulated with several concentrations of metal salts (CoCl2, NiCl2, CrCl3 × 6H2O) to analyze viability, gene expression, protein release and ROS production. Untreated cells served as negative controls. While exposure to Cr(3+) did not influence cell viability in both cell types, the highest concentration (500 µM) of Co(2+) and Ni(2+) showed cytotoxic effects mirrored by significantly reduced metabolism, cell number and a concomitant increase of ROS. The release of IL-1β, IL-8, MCP-1 and M-CSF proteins was mainly affected in macrophages after metal ion exposure (100 µM), indicating a higher impact on pro-inflammatory activity. Our results prove that monocytes and macrophages react very sensitively to corrosion products. High concentrations of bivalent ions lead to cell death, while lower concentrations trigger the release of inflammatory mediators, mainly in macrophages.

scholarly journals An unusual metal ion configuration in a viral DNA-packaging nuclease active site

2014 ◽  
Vol 70 (a1) ◽  
pp. C489-C489
Author(s):  
Haiyan Zhao ◽  
Theodore Christensen ◽  
Zihan Lin ◽  
Annie Lynn ◽  
Liang Tang
Keyword(s):  
Nucleic Acid ◽  
Metal Ions ◽  
Active Site ◽  
Short Distance ◽  
Metal Ion ◽  
Catalytic Mechanism ◽  
Dna Packaging ◽  
Viral Dna ◽  
Viral Dna Packaging ◽  
Ion Cluster

Nucleic acid metabolism is fundamental to many biological processes. A large class of enzymes such as RNase H, reverse transcriptase, retroviral integrase, topoisomerase, DNA and RNA polymerase, transposase, Holliday-junction resolvase, RNAi slicer Argonaute, and viral DNA-packaging terminase, utilize a common two-metal-ion catalytic mechanism for cleavage or synthesis of nucleic acid chains. Here we report an unusual metal-ion cluster in the active site of the nuclease domain of a viral DNA-packaging terminase unveiled by X-ray structures up to 1.38 Angstrom resolution. Two Mg2+ ions are situated in a coupled octahedral coordination system with liganding oxygen atoms from aspartic acid residues as well as water molecules. The two Mg2+ ions are located within a strikingly short distance of ~2.5 Å, which is unusual given the 1.6 Å atomic radius of Mg2+ and is shorter than previously observed metal-metal distances in metallocluster-containing enzymes or other biological systems. This provides the structural basis for distinguishing Mg2+ from other metal ions such as Ca2+ which are well known to support binding of the nucleic acid substrate but not support catalysis. Such an ultra-short distance between two metal-ions may be essential for generation of a highly positive niche, leading to nucleophilic attack at the phosphodiester bond of DNA. These results have defined the precise chemical configuration of the active site in nucleases using two-metal-ion catalytic mechanism. Moreover, assembly of this two-metal-ion cluster in the viral DNA-packaging terminase is mediated by an adjacent Lys residue, likely serving as a regulatory mechanism for activation of the nuclease activity of the terminase during packaging of viral genome.

scholarly journals Cyclophospholipids Increase Protocellular Stability to Metal Ions

2019 ◽  
Author(s):  
Ö. Duhan Toparlak ◽  
Megha Karki ◽  
Veronica Egas Ortuno ◽  
Ramanarayanan Krishnamurthy ◽  
Sheref Mansy
Keyword(s):  
Fatty Acids ◽  
Life Cycle ◽  
Metal Ions ◽  
Metal Ion ◽  
Narrow Range ◽  
Ion Concentration ◽  
Darwinian Evolution ◽  
Early Earth ◽  
Biological Polymers ◽  
High Concentrations

<p>Model protocells have long been constructed with fatty acids, because these lipids are prebiotically plausible and can, at least theoretically, support a protocell life cycle. However, fatty acid protocells are stable only within a narrow range of pH and metal ion concentration. This instability is particularly problematic as the early Earth would have had a range of conditions, and life as we know it is completely reliant on metal ions for catalysis and the folding and activity of biological polymers. Here we show that prebiotically plausible monoacyl cyclophospholipids form robust vesicles that survive a broad range of pH and high concentrations of Mg2+, Ca2+, and Na+. Importantly, stability to Mg2+ and Ca2+ is improved by the presence of environmental concentrations of Na+. These results suggest that cyclophospholipids, or lipids with similar characteristics, may have played a central role during the emergence of Darwinian evolution.</p>

scholarly journals Mechanistic and In silico Characterization of Metal ion Requirements of Escherichia coli Zinc Phosphodiesterase Activity

2020 ◽  
Vol 5 (1) ◽  
pp. 56-65
Author(s):  
Adedoyin Igunnu ◽  
Micheal F. Dada ◽  
Tamonokorite AbelJack-Soala ◽  
Ireoluwa Y. Joel ◽  
Oluwafunmibi O. Lanre-Ogun ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Metal Ions ◽  
Binding Affinity ◽  
Metal Ion ◽  
Phosphoryl Transfer ◽  
Phosphodiesterase Activity ◽  
Divalent Metal Ions ◽  
Nitrophenyl Phosphate ◽  
In Silico Characterization ◽  
Affinity Score

AbstractZinc phosphodiesterase (ZiPD) participates in the maturation of tRNA precursors. The roles of metal ions in promoting phosphoryl transfer reaction on zinc phosphodiesterase (ZiPD) activity have not been fully characterized. Therefore, this study investigated the effects of some metal ions on phosphodiesterase activity of Escherichia coli ZiPD as well as the binding site and binding affinity of the metal ions. ZiPD activity was measured by monitoring the rate of hydrolysis of bis-para-nitrophenyl phosphate (bis-pNPP) in the presence of some selected divalent metal ions (Mn2+, Co2+, Mg2+ and Zn2+). The results obtained revealed that Mn2+ at 1 mM activated ZiPD activity by 4-fold with binding affinity score of 1.795. Co2+ at 0.5 mM activated ZiPD activity by 2-fold with binding affinity score of 1.773. Mg2+ at 0.5 mM enhanced the binding affinity of ZiPD for bis-pNPP but did not increase the turnover rate of ZiPD. Zn2+ at 1.5 mM activated ZiPD activity by 2-fold via increased affinity of ZiPD for bis-pNPP. In conclusion, the findings from this study showed that Mn2+ and Zn2+ are the most effective stimulatory ions of ZiPD for bis-pNPP while Zn2+ exerted the highest binding affinity of ZiPD for bis-pNPP.

Nanopore analysis of the interaction of metal ions with prion proteins and peptidesThis paper is one of a selection of papers published in this special issue entitled “Canadian Society of Biochemistry, Molecular & Cellular Biology 52nd Annual Meeting — Protein Folding: Principles and Diseases” and has undergone the Journal's usual peer review process.

2010 ◽  
Vol 88 (2) ◽  
pp. 347-358 ◽  
Author(s):  
Radu I. Stefureac ◽  
Claudia Avis Madampage ◽  
Olga Andrievskaia ◽  
Jeremy S. Lee
Keyword(s):  
Metal Ions ◽  
Conformational Changes ◽  
Metal Ion ◽  
Prion Proteins ◽  
Peer Review Process ◽  
Cellular Biology ◽  
Divalent Metal Ions ◽  
High Concentrations ◽  
Individual Peptide ◽  
Selection Of

Nanopore analysis can be used to study conformational changes in individual peptide or protein molecules. Under an applied voltage there is a change in the event parameters of blockade current or time when a molecule bumps into or translocates through the pore. If a molecule undergoes a conformational change upon binding a ligand or metal ion the event parameters will be altered. The objective of this research was to demonstrate that the conformation of the prion protein (PrP) and prion peptides can be modulated by binding divalent metal ions. Peptides from the octarepeat region (Octa2, (PHGGGWGQ)2 and Octa 4, (PHGGGWGQ)4), residues 106–126 (PrP106–126), and the full-length Bovine recombinant prion (BrecPrP) were studied with an α-hemolysin pore. Octa2 readily translocated the pore but significant bumping events occurred on addition of Cu(II) and to a lesser extent Zn(II), demonstrating that complex formation was occurring with concomitant conformational changes. The binding of Cu(II) to Octa4 was more pronounced and at high concentrations only a small proportion of the complex could translocate. Addition of Zn(II) also caused significant changes to the event parameters but Mg(II) and Mn(II) were inert. Addition of Cu(II) to PrP106–126 caused the formation of a very tight complex, which could not translocate the pore. Small changes were observed with Zn(II), but not with Mg(II) or Mn(II). Analysis of BrecPrP showed that about 37% were translocation events, but on addition of Cu(II) or Zn(II) these disappeared and only bumping events were recorded. Suprisingly, addition of Mn(II) caused an increase in translocation events to about 64%. Thus, conformational changes to prions upon binding metal ions are readily observed by nanopore analysis.

Sign in / Sign up

Export Citation Format

Share Document