scholarly journals Metal ion effects on Polyphenol Oxidase Covalently immobilized on a Bio-Composite

2021 ◽  
Vol 67 (2) ◽  
pp. 50-55
Author(s):  
Serap Beyaztaş Uzunoğlu ◽  
Tayfun Uzunoğlu ◽  
Samet Koçsuz ◽  
Murat Evyapan ◽  
Oktay Arslan
Keyword(s):  
Metal Ions ◽  
Polyphenol Oxidase ◽  
Metal Ion ◽  
Immobilized Enzyme ◽  
Competitive Inhibition ◽  
Enzyme Concentration ◽  
Free Enzyme ◽  
Ic50 Values ◽  
Metal Ion Effects

Biosensors can be developed using different immobilization methods. Interest in immobilization methods have increased because biosensors have been important for science. Polyphenol oxidase (PPO) was used generally in biosensor applications. For this purpose, Polyphenol oxidase from banana was purified and covalently immobilized on chitosan-gelatin bio-composite. The properties of immobilized enzyme were investigated and compared to free enzyme. Various parameters were studied such as pH, temperature and storage stability on immobilized and free enzyme. Kinetic parameters were also evaluated by different substrates on immobilized and free enzyme. Catechol was determined the best substrate for immobilized enzyme with optimum condition. In vitro effects of metal ions were studied on immobilized enzyme. Concentration range of metal ions is 1.0-10.0 x10-6 mol/L. The activity of immobilized PPO was increased by Fe+2 and Ag+1 ion. Co+3 and Cu+1 had very strong inhibitory effects with IC50 values of 19.69x10-3 mol/L and 23.49 x10-3 mol/L, respectively. Inhibition constants (Ki) and inhibition types of metal ions were determined with immobilized enzyme. Zn+2 and Cr+3 ions were showed competitive inhibition and Pb+2 ions were determined non-competitive inhibition with immobilized enzyme. Mixed type inhibition was obtained with Co+3 ion using catechol as substrate with 3.33x10-5 mol/L Ki value on immobilized PPO. Immobilized PPO can be evaluated for biosensor for the purpose of measurements of metal ions.

scholarly journals In vitro effects of some metal ions on glutathione reductase in the gills and liver of Capoeta trutta

2017 ◽  
Vol 8 (1) ◽  
pp. 66-70 ◽  
Author(s):  
M. Kirici ◽  
M. Atamanalp ◽  
M. Kirici ◽  
Ş. Beydemir
Keyword(s):  
Metal Ions ◽  
Glutathione Reductase ◽  
Metal Ion ◽  
Specific Activity ◽  
Sodium Dodecyl ◽  
Inhibitory Effects ◽  
Fish Liver ◽  
Fish Gill ◽  
Ic50 Values

Many aquatic environmental problems have arisen in consequence of contamination of water by toxic metals and organic pollutants in the present age of technology. Metals play vital roles in enzyme activities and other metabolic events due to their bioaccumulative and nonbiodegradable properties among aquatic pollutants. The aim of this study was to evaluate the inhibitory effects of some metal ions (Ag+, Cu2+, Co2+, Ni2+, Pb2+ and Zn2+) on Capoeta trutta gill and liver glutathione reductase (EC: 1.8.1.7; GR). For this purpose, initially, GR was purified from C. trutta gill and liver. Purification procedure consisted of three steps; preparation of hemolysate, ammonium sulphate precipitation and 2’, 5’-ADP Sepharose 4B affinity chromatography. Using this procedure, C. turtta gill GR, having the specific activity of 19.111 EU/mg proteins, was purified with a yield of 38.8% and 910.05-fold; C. trutta liver GR, having the specific activity of 16.167 EU/mg proteins, was purified with a yield of 21.1% and 734.86-fold. The purity of the enzymes was checked on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and each purified enzyme showed a single band on the gel. In addition, inhibitory effects of some metal ions (Ag+, Cu2+, Co2+, Ni2+, Pb2+ and Zn2+) on GR from gill and liver were investigated in vitro. Ki constants and IC50 values for metal ions which showed inhibition effects were determined by Lineweaver-Burk graps and plotting activity % vs. [I]. In conclusion, IC50 values for fish gill GR were 0.000625, 0.153, 0.220, 0.247 and 0.216 mM and Ki constants for fish gill GR were 0.00045 ± 0.00008, 0.128 ± 0.036, 0.182 ± 0.138, 0.482 ± 0.219 and 0.112 ± 0.047 mM for Ag+, Cu2+, Co2+, Ni2+, Pb2+ and Zn2+, respectively. IC50 values for fish liver GR were 0.000437, 0.217, 0.185, 0.355 and 0.349 mM and Ki constants for fish liver GR were 0.00025 ± 0.00013, 0.532 ± 0.146, 0.123 ± 0.066, 0.093 ± 0.020 and 0.151 ± 0.084 mM for Ag+, Cu2+, Co2+, Ni2+, Pb2+ and Zn2+, respectively. In vitro inhibition rank order was determined as Ag+ > Co2+ > Zn2+ > Ni2+ > Pb2+ for fish gill GR; Ag+ > Cu2+ > Co2+ > Pb2+ > Ni2+ for fish liver GR. From these results, we showed that Ag+ metal ion is the most potent inhibitor of GR enzyme on gill and liver tissues. 

scholarly journals In vitro Antioxidant Potentials of Ethanol Extract of Unripe and Ripe Dennetia tripetala Fruits

2019 ◽  
pp. 1-8
Author(s):  
E. I. Akpakpan ◽  
E. N. Onyeike ◽  
C. U. Ogunka-Nnoka
Keyword(s):  
Vitamin C ◽  
Competitive Inhibition ◽  
Reducing Power ◽  
Ethanol Extract ◽  
Natural Antioxidants ◽  
In Vitro Models ◽  
Scavenging Activity ◽  
Fruit Extract ◽  
Ic50 Values

Dennettia tripetala fruit is a popular Nigerian fruit from the family of plant known as Annonaceae. The whole fruit (flesh and seed) is usually consumed as snacks and it is oftentimes consumed with local gin (ufofop in Ibibio or kaikai in Igbo) or added to dishes as spice due to its peculiar strong pepperish taste and sweet aroma. The present study is aimed at evaluating the antioxidant potentials of ethanol extract of ripe and unripe D. tripetala (DT) fruit in vitro. The antioxidant activity of the ethanol extract of DT was evaluated spectrophotometrically using various in vitro models like 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) and hydrogen peroxide scavenging activity; metal chelating activity and reducing power. Vitamin C was used as the standard antioxidant.Unripe and ripe DT fruits, as well as vitamin C showed a competitive inhibition of DPPH and H2O2 free radicals. As concentration of the extracts increased from 20 to100 µg/mL, the % scavenging activity for vitamin C increased from 87.86 ± 0.11 to 90.66 ± 0.07 and for ripe DT fruits from 15.15 ± 0.24 to 25.52 ± 0.23, while for unripe, fruits values increased from 12.09 ± 0.35 to 23.06 ± 0.12. The IC50 values was highest in unripe (549.23) followed by ripe (276.63) and lowest in vitamin C (12.92) indicating that vitamin C was the best scavenger of DPPH radical. Similar trend was obtained for H2O2 scavenging activity as well as reducing power. Unripe DT fruit extract was more potent at chelating metal ions (IC50 was 95.38), followed by the standard ascorbic acid with IC50 of 97.03 and was lowest in ripe DT fruit extract with IC50 value of 124.66. Unripe and ripe DT are potent antioxidants in nature and may be used to supplement our diets as rich sources of natural antioxidants for health protection.

scholarly journals A trapped human PPM1A–phosphopeptide complex reveals structural features critical for regulation of PPM protein phosphatase activity

2018 ◽  
Vol 293 (21) ◽  
pp. 7993-8008 ◽  
Author(s):  
Subrata Debnath ◽  
Dalibor Kosek ◽  
Harichandra D. Tagad ◽  
Stewart R. Durell ◽  
Daniel H. Appella ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Metal Ions ◽  
Active Site ◽  
Metal Binding ◽  
Metal Ion ◽  
Catalytic Domain ◽  
Protein Phosphatases ◽  
Random Order ◽  
Structural Features

Metal-dependent protein phosphatases (PPM) are evolutionarily unrelated to other serine/threonine protein phosphatases and are characterized by their requirement for supplementation with millimolar concentrations of Mg2+ or Mn2+ ions for activity in vitro. The crystal structure of human PPM1A (also known as PP2Cα), the first PPM structure determined, displays two tightly bound Mn2+ ions in the active site and a small subdomain, termed the Flap, located adjacent to the active site. Some recent crystal structures of bacterial or plant PPM phosphatases have disclosed two tightly bound metal ions and an additional third metal ion in the active site. Here, the crystal structure of the catalytic domain of human PPM1A, PPM1Acat, complexed with a cyclic phosphopeptide, c(MpSIpYVA), a cyclized variant of the activation loop of p38 MAPK (a physiological substrate of PPM1A), revealed three metal ions in the active site. The PPM1Acat D146E–c(MpSIpYVA) complex confirmed the presence of the anticipated third metal ion in the active site of metazoan PPM phosphatases. Biophysical and computational methods suggested that complex formation results in a slightly more compact solution conformation through reduced conformational flexibility of the Flap subdomain. We also observed that the position of the substrate in the active site allows solvent access to the labile third metal-binding site. Enzyme kinetics of PPM1Acat toward a phosphopeptide substrate supported a random-order, bi-substrate mechanism, with substantial interaction between the bound substrate and the labile metal ion. This work illuminates the structural and thermodynamic basis of an innate mechanism regulating the activity of PPM phosphatases.

Comparative inhibition of hepatic hydroxymethylbilane synthase by both hard and soft metal cations

1984 ◽  
Vol 62 (1) ◽  
pp. 49-54 ◽  
Author(s):  
D. J. Farmer ◽  
B. R. Hollebone
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Ph Dependence ◽  
Sprague Dawley ◽  
Sprague Dawley Rats ◽  
Wide Range ◽  
Chemical Behaviour ◽  
Soft Metal ◽  
Hardness Values

The in vitro inhibition of hydroxymethylbilane synthase (EC 4.3.1.8, uroporphyrinogen I synthetase) obtained from livers of Sprague–Dawley rats has been studied with a wide range of di- and tri-valent metal ions. After purification by cell lysis, heat treatment, and centrifugation, the stable, soluble enzyme yielded sigmoidal inhibition curves with increasing concentrations of each of the 16 test ions. Using the negative logarithm of metal concentration for 50% inhibition (the pM50 value), the metal ions could be classified according to their Klopman hardness values. Very soft ions including Hg2+, intermediate ions including Cr3+, and very hard ions including Al3+ all yielded large pM50 values indicating strong inhibition. In comparison to known metal-ion chemical behaviour, these three ions could indicate three different types of inhibitory binding sites at or near the active site: Hg2+ corresponding to sulfur in cysteine, Cr3+ corresponding to nitrogen in histidine, and Al3+ corresponding to oxygen in carboxyl groups. The presence of the first two sites is also indicated by the pH dependence of activity.

scholarly journals Chemical profiling, in vitro antioxidant and antidiabetic assessment of flavonoids from the ethanol extract of Hermannia geniculata root

2021 ◽  
Vol 19 (1) ◽  
pp. 1-13
Author(s):  
L.A. Adeniran ◽  
C.P. Palanisamy ◽  
A.O.T. Ashafa
Keyword(s):  
Competitive Inhibition ◽  
Antioxidant Properties ◽  
Reactive Oxygen ◽  
Ethanol Extract ◽  
Kinetic Studies ◽  
Retention Factor ◽  
Chemical Profiling ◽  
Ic50 Values ◽  
Inhibitory Potential

Determination of the in vitro antioxidant and the inhibitory potential of flavonoids from Hermannia geniculata (FHG) roots on diabetes-linked enzymes was carried out. The chemical profiling of FHG roots extract was investigated using High Pressure Thin Layer Chromatography (HPTLC) fingerprint analysis. The reactive oxygen scavenging potential of the extract was analyzed. Starch solution (1%) was reacted with different concentrations of FHG extract to determine the α-amylase inhibitory potential of the extract while α- glucosidase inhibition assay was carried out through incubation of different concentrations of the extract followed by addition of p-ntrophenyl-α-Dglucopyranoside solution. HPTLC results indicated the presence of flavonoids/ phenolcarboxylic acid, and Kaemferol (Rf 0.80) were detected in the extract with retention factor Rf. ranging from 0.08 to 0.95. FHG extract showed commendable antioxidant properties with IC50 values (3.07± 0.12, 2.13± 0.67) µg/mL for 1, 1-diphenyl-2- picrylhydrazyl (DPPH) and 2, 2-azino-bis (3- ethylbenzothiazoline-6-sulphonic) acid (ABTS) radicals which were lower and significantly different (p<0.05) compared to standard silymarin with IC50: (3.55± 0.10, 2.77± 0.75) µg/mL for DPPH and ABTS respectively. The results indicated mild inhibition of α-amylase with IC50: (5.55± 0.37) µg/mL which was higher and significantly different (p<0.05) from acarbose with IC50: (3.81± 0.29) µg/mL. Moreover, the extract showed 73% inhibition of α-glucosidase. Kinetic studies of FHG extract revealed competitive and mixed non-competitive inhibition of α- amylase and α-glucosidase respectively. This study indicated FHG capabilities of scavenging reactive oxygen species and reducing hydrolysis of starch responsible for post-prandial hyperglyceamia seen in type 2 diabetes mellitus. Keywords: Antidiabetic, Antioxidant, Flavonoids, Hermannia geniculate, HPTLC

scholarly journals Release of metal ions from fixed orthodontic appliance: An in vitro study in continuous flow system

2013 ◽  
Vol 84 (1) ◽  
pp. 140-148 ◽  
Author(s):  
Marcin Mikulewicz ◽  
Katarzyna Chojnacka ◽  
Paulina Wołowiec
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Ion Concentration ◽  
Emission Spectrometry ◽  
Orthodontic Appliances ◽  
Orthodontic Appliance ◽  
Toxic Dose ◽  
Fixed Orthodontic Appliances ◽  
Fixed Orthodontic Appliance

ABSTRACT Objective: To evaluate the release of metal ions from fixed orthodontic appliances. Materials and Methods: A new system for in vitro testing of dental materials was constructed and consisted of a thermostatic glass reactor that enabled immersion of the studied material. Experimental conditions reflected the human oral cavity, with a temperature of 37°C and a saliva flow rate of 0.5mL/min. The simulated fixed orthodontic appliance made of stainless steel was evaluated. Sampling was performed at several time points during the 28-day study, and the metal ion concentration was determined by inductively coupled plasma optical emission spectrometry. Results: The total mass of released metal ions from the appliance during 4 weeks of the experiment was as follows nickel 18.7 μg, chromium 5.47 μg, copper 31.3 μg. Conclusions: The estimated doses of nickel, chromium, and copper determined by extrapolation of experimental data released during the treatment period were far below the toxic dose to humans. This shows that orthodontic treatment might not be a significant source of exposure to these metal ions.

Activation and inactivation of acetylcholinesterase by metal ions

1981 ◽  
Vol 59 (9) ◽  
pp. 728-735 ◽  
Author(s):  
George Tomlinson ◽  
Bulent Mutus ◽  
Ian McLennan
Keyword(s):  
Ionic Strength ◽  
Metal Ions ◽  
Metal Ion ◽  
Prolonged Exposure ◽  
Chelating Agent ◽  
High Ionic Strength ◽  
Metal Ion Binding ◽  
Peripheral Site ◽  
Metal Ion Effects ◽  
Low Ionic Strength

The kinetic consequences of acetylcholinesterase peripheral site occupation by metal ions were examined using three substrates; acetylthiocholine, p-nitrophenylacetate, and 7-(dimethylcarbamoyloxy)-N-methylquinolinium iodide. Two classes of metal ion effects were noted: activation by a group including Mg2+, Ca2+, Mn2+, and Na+, and inactivation by a second group which to date includes Zn2+, Cd2+, Hg2+, Ni2+, Cu2+, and Pb2+. Activation is demonstrable only in solutions of low ionic strength whereas inactivation can be readily observed in solutions of both low and high ionic strength. Activation appears to be due to a combination of metal ion binding and ionic strength effects and involves binding to peripheral sites which are distinct from those which bind organic cationic activators such as gallamine, propidium, and 7-(dimethylcarbamoyloxy)-N-methylquinolinium. The principal activating effect is on the deacylation phase of the enzyme–substrate reaction. Inactivators effect a slow conversion of the enzyme to an unreactive form. The kinetics of inactivation are biphasic at low ionic strength but become essentially monophasic at high ionic strength. More than 80% of the enzyme activity can be recovered upon addition of EDTA provided the chelating agent is added immediately following completion of the inactivation process. Prolonged exposure to inactivators results in a progressive decrease in the amount of recoverable activity. Although peripheral ligand interactions may result in a variety of catalytic site conformations, the macroscopic properties can be accounted for in terms of three ligand-dependent states of the enzyme in which catalytic ability (actual or potential) is retained, and a fourth denatured state.

Synthesis, crystal structure and biological properties of Cd and Zn coordination polymers based on a flexible tripodal ligand

2019 ◽  
Vol 75 (7) ◽  
pp. 1002-1010 ◽  
Author(s):  
Xia Wang ◽  
Ning Ling ◽  
Hanbing Li ◽  
Xiaohe Xiao ◽  
Yawen Zhang
Keyword(s):  
Metal Ions ◽  
Coordination Polymers ◽  
Metal Ion ◽  
Radical Scavenging ◽  
Antidiabetic Activity ◽  
Distorted Octahedral Geometry ◽  
Hydrothermal Conditions ◽  
X Ray ◽  
Methyl Benzene

Two new coordination polymers, namely poly[[hexathiocyanatotetrakis{μ3-2,4,6-trimethyl-1,3,5-tris[(triazol-1-yl)methyl]benzene}tricadmium(II)] 3.5-hydrate], {[Cd3(SCN)6(C18H21N9)4]·3.5H2O} n (1), and poly[[hexathiocyanatotetrakis{μ3-2,4,6-trimethyl-1,3,5-tris[(triazol-1-yl)methyl]benzene}trizinc(II)] 3.5-hydrate], {[Zn3(SCN)6(C18H21N9)4]·3.5H2O} n (2), have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction analysis. From the X-ray analysis, it is noteworthy that polymers 1 and 2 are isostructural, with their three-dimensional structures composed of three kinds of four-connection metal ions and two kinds of three-connection 2,4,6-trimethyl-1,3,5-tris[(triazol-1-yl)methyl]benzene (TTTMB) ligand nodes. Each metal ion is six-coordinated in a slightly distorted octahedral geometry. The antioxidant activity against DPPH (2,2-diphenyl-1-picrylhydrazyl) and the antidiabetic activity against α-amylase of the synthesized compounds were evaluated in vitro. The results of the DPPH free-radical scavenging assay showed that polymers 1 and 2 exhibited strong antioxidant effects, with IC50 values of 3.81 and 2.56 mg ml−1, respectively. The IC50 value in the antidiabetic studies of polymer 1 was 3.94 mg ml−1, while polymer 2 exhibited no antidiabetic activity. Polymers 1 and 2 revealed different inhibitory activities on DPPH and α-amylase, which indicated that the metal ions play important roles in the biological activity of coordination polymers. In addition, the solid-state photoluminescence properties and thermal stability of 1 and 2 have been investigated.

scholarly journals Enzymes of heme metabolism is the kidney. Regulation by trace metals which do not form heme complexes

1977 ◽  
Vol 146 (5) ◽  
pp. 1286-1293 ◽  
Author(s):  
MD Maines ◽  
A Kappas
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Early Period ◽  
Reciprocal Relationship ◽  
Central Metal ◽  
Ion Regulation ◽  
Heme Metabolism ◽  
Rate Limiting

The in vivo regulation by metal ions of the enzymes of heme metabolism in kidney-particularly of ALAS, the rate-limiting enzyme in heine formation- was investigated. Ni(2+) and Pt(4+), metals which do not enzymatically form metalloporphyrins, were found to regulate ALAS in kidney as they do in liver. The pattern of this regulation was generally similar to that observed with heme and metal ions in liver, i.e., a late increase in enzyme activity after an early period in which ALAS activity was unaltered or inhibited. The metals did not interact with the enzyme in vitro to alter its activity. In this study no direct reciprocal relationship between ALAS activity and total cellular heine content was demonstrated. The metal ions, particularly Pt(4+), also altered the activity of other enzymes of heme biosynthesis in kidney. Pt(4+) severely inhibited the activity of ALAD and UROS. Ni(2+) and Pt(4+) were potent inducers of heme oxygenase, the initial and rate-limiting enzyme in heine degradation. It is proposed that the physiological regulation of ALAS is mediated through the action of metal ions, rather than by the cellular content of heine, and that the regulation of ALAS by heine reflects the action of the central metal ion of heme rather than that of the entire metalloporphyrin complex. In this proposed mechanism for metal ion regulation of ALAS, the tetrapyrrole moiety of heine is considered to function principally as an efficient carrier of metal to the regulatory site for ALAS production, inasmuch as the tetrapyrrole ring itself has been shown in earlier studies not to have any effect on ALAS activity. The production of heine oxygenase is believed to be similarly regulated.

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