scholarly journals Plausible molecular mechanism for activation by fumarate and electron transfer of the dopamine β-mono-oxygenase reaction

2002 ◽  
Vol 367 (1) ◽  
pp. 77-85 ◽  
Author(s):  
D. Shyamali WIMALASENA ◽  
Samantha P. JAYATILLAKE ◽  
Donovan C. HAINES ◽  
Kandatege WIMALASENA
Keyword(s):  
Electron Transfer ◽  
Molecular Mechanism ◽  
Geometric Isomer ◽  
Enzyme Activation ◽  
Reduced Form ◽  
Electrostatic Model ◽  
Steady State Kinetic ◽  
Low Concentrations ◽  
Substrate Inhibitor ◽  
Inhibition Potency

A series of fumarate analogues has been used to explore the molecular mechanism of the activation of dopamine β-mono-oxygenase by fumarate. Mesaconic acid (MA) and trans-glutaconic acid (TGA) both activate the enzyme at low concentrations, similar to fumarate. However, unlike fumarate, TGA and MA interact effectively with the oxidized enzyme to inhibit it at concentrations of 1—5mM. Monoethylfumarate (EFum) does not activate the enzyme, but inhibits it. In contrast with TGA and MA, however, EFum inhibits the enzyme by interacting with the reduced form. The saturated dicarboxylic acid analogues, the geometric isomer and the diamide of fumaric acid do not either activate or inhibit the enzyme. The phenylethylamine—fumarate conjugate, N-(2-phenylethyl)fumaramide (PEA-Fum), is an 600-fold more potent inhibitor than EFum and behaves as a bi-substrate inhibitor for the reduced enzyme. The amide of PEA-Fum behaves similarly, but with an inhibition potency 20-fold less than that of PEA-Fum. The phenylethylamine conjugates of saturated or geometric isomers of fumarate do not inhibit the enzyme. Based on these findings and on steady-state kinetic analysis, an electrostatic model involving an interaction between the amine group of the enzyme-bound substrate and a carboxylate group of fumarate is proposed to account for enzyme activation by fumarate. Furthermore, in light of the recently proposed model for the similar copper enzyme, peptidylglycine α-hydroxylating mono-oxygenase, the above electrostatic model suggests that fumarate may also play a role in efficient electron transfer between the active-site copper centres of dopamine β-mono-oxygenase.

Electron Transfer in Electro-Oxidation of Amoxicillin Using Platinum Electrode and Platinum Modified Cobalt Electrodes

2021 ◽  
Vol 874 ◽  
pp. 155-164
Author(s):  
Herlina ◽  
Muhammad Ali Zulfikar ◽  
Buchari
Keyword(s):  
Electron Transfer ◽  
Oxidation Process ◽  
Platinum Electrode ◽  
Linear Sweep Voltammetry ◽  
Pharmaceutical Product ◽  
Electrochemical Methods ◽  
Linear Sweep ◽  
Low Concentrations ◽  
Electro Oxidation ◽  
Continuous Use

Recently, the increased use of antibiotics in the environment has been studied and one of them is amoxicillin. Amoxicillin (AMX) is a pharmaceutical product that can become waste due to the continuous use and released into the ecosystem even at low concentrations. The electro-oxidation process is one of the electrochemical methods used to destruct the existence of antibiotics because the process is relatively fast and inexpensive. Platinum electrode and platinum modified cobalt electrodes are used for amoxicillin electro-oxidation at the pH of 2 - 7. The range of this amoxicillin's pH was achieved by the pKa's values of the amoxicillin and measured using a UV/Vis spectrophotometer. Electron transfer during the amoxicillin electro-oxidation process with these electrodes is measured by linear sweep voltammetry. The results obtained during the electro-oxidation process showed that electron transfer of amoxicillin was 1, with a Nernstian factor of 0.0521 V/pH for platinum electrode and platinum modified cobalt electrodes, Pt/Co(OH)2 and Pt/Co respectively with values of 0.0506 V/pH and 0.0673 V/pH.

Effect of Azide on the ATPase Activity of Isolated CF1

1991 ◽  
Vol 46 (7-8) ◽  
pp. 621-628 ◽  
Author(s):  
Ignat B. Minkov ◽  
Heinrich Strotmann
Keyword(s):  
Atpase Activity ◽  
Enzyme Activation ◽  
Applied Method ◽  
Spinach Chloroplasts ◽  
Dependent Atpase ◽  
Low Concentrations ◽  
Activation Heat

Abstract The effect of azide on M g2+-and Ca2+-dependent ATPase of differently activated CF1 isolated from spinach chloroplasts was studied. It is shown that Mg2+-ATPase activity is sensitive towards azide irrespective of the applied method of enzyme activation. Heat-or trypsin-acti-vated Ca2+-ATPase is also inhibited, whereas methanol-and octylglucoside-stimulated or DTT-activated Ca2+-ATPase is not affected by azide. Preincubation of the DTT-activated enzyme with low concentrations of Mg2+ induces azide susceptibility of the Ca2+-dependent ATPase.

Electrochemical dehydrogenase-based homogeneous assays in whole blood

1995 ◽  
Vol 41 (4) ◽  
pp. 591-598 ◽  
Author(s):  
H Yao ◽  
H B Halsall ◽  
W R Heineman ◽  
S H Jenkins
Keyword(s):  
Electron Transfer ◽  
Flow Injection ◽  
Flow Injection Analysis ◽  
Whole Blood ◽  
Electrochemical Method ◽  
Reduced Form ◽  
Glucose Assay ◽  
Coupling Reagent ◽  
Homogeneous Assays ◽  
Assay Conditions

Abstract An electrochemical method has been developed for determining NADH in whole blood for dehydrogenase-based assays by flow-injection analysis. NADH generated by dehydrogenase is oxidized by an electron-transfer coupling reagent, 2,6-dichloroindophenol (DCIP). The reduced form of DCIP (DCIPH2) is measured amperometrically by flow-injection analysis. Endogenous interferents were inhibited by p-hydroxymercuribenzoate. Electrode fouling by proteins was not observed under assay conditions. The Emit theophylline enzyme immunoassay and the hexokinase glucose assay were used as models. For the glucose assay, the intraassay CVs were 15% at 0.31 g/L and 3.5% at 1.82 g/L. Recoveries of glucose from whole blood (compared with that for aqueous standards) were 109%, 97.9%, and 101% at 0.050, 2.00, and 5.00 g/L glucose, respectively, and 104%, 101%, and 102% for theophylline at concentrations of 5.0 (low), 16.4 (medium), and 30.2 (high) mg/L, respectively, with corresponding precisions of 12%, 9.5%, and 8.8%. Both assays correlated well with results by reference methods. These studies demonstrate that this method can measure NADH in whole blood without prior separation and that it is potentially applicable to other dehydrogenase-based assays in whole blood.

scholarly journals Inhibition of Transferrin Recycling and Endosome Tubulation by Phospholipase A2Antagonists

2001 ◽  
Vol 276 (50) ◽  
pp. 47361-47370 ◽  
Author(s):  
Paul de Figueiredo ◽  
Anne Doody ◽  
Renée S. Polizotto ◽  
Daniel Drecktrah ◽  
Salli Wood ◽  
...  
Keyword(s):  
Cell Surface ◽  
Molecular Mechanism ◽  
Golgi Complex ◽  
Broad Spectrum ◽  
Tubule Formation ◽  
Recycling Endosomes ◽  
Low Concentrations ◽  
A Cell ◽  
Recycling Pathway ◽  
Lines Of Evidence

We report here that a broad spectrum of phospholipase A2(PLA2) antagonists produce a concentration-dependent, differential block in the endocytic recycling pathway of transferrin (Tf) and Tf receptors (TfRs) but have no acute affect on Tf uptake from the cell surface. At low concentrations of antagonists (∼1 μm), Tf and TfR accumulated in centrally located recycling endosomes, whereas at higher concentrations (∼10 μm), Tf-TfR accumulated in peripheral sorting endosomes. Several independent lines of evidence suggest that this inhibition of recycling may result from the inhibition of tubule formation. First, BFA-stimulated endosome tubule formation was similarly inhibited by PLA2antagonists. Second, endocytosed tracers were found in larger spherical endosomes in the presence of PLA2antagonists. And third, endosome tubule formation in a cell-free, cytosol-dependent reconstitution system was equally sensitive PLA2antagonists. These results are consistent with the conclusion that endosome membrane tubules are formed by the action of a cytoplasmic PLA2and that PLA2-dependent tubules are involved in intracellular recycling of Tf and TfR. When taken together with previous studies on the Golgi complex, these results also indicate that an intracellular PLA2activity provides a novel molecular mechanism for inducing tubule formation from multiple organelles.

A cytochrome c mutant with high electron transfer and antioxidant activities but devoid of apoptogenic effect

2002 ◽  
Vol 362 (3) ◽  
pp. 749-754 ◽  
Author(s):  
Ziedulla Kh. ABDULLAEV ◽  
Marina E. BODROVA ◽  
Boris V. CHERNYAK ◽  
Dmitry A. DOLGIKH ◽  
Ruth M. KLUCK ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Cytochrome C ◽  
Antioxidant Activities ◽  
H2o2 Production ◽  
High Electron ◽  
Wild Type ◽  
Low Concentrations ◽  
Rat Heart Mitochondria ◽  
The Difference ◽  
Α Helix

A cytochrome c mutant lacking apoptogenic function but competent in electron transfer and antioxidant activities has been constructed. To this end, mutant species of horse and yeast cytochromes c with substitutions in the N-terminal α-helix or position 72 were obtained. It was found that yeast cytochrome c was much less effective than the horse protein in activating respiration of rat liver mitoplasts deficient in endogenous cytochrome c as well as in inhibition of H2O2 production by the initial segment of the respiratory chain of intact rat heart mitochondria. The major role in the difference between the horse and yeast proteins was shown to be played by the amino acid residue in position 4 (glutamate in horse, and lysine in yeast; horse protein numbering). A mutant of the yeast cytochrome c containing K4E and some other ‘horse’ modifications in the N-terminal α-helix, proved to be (i) much more active in electron transfer and antioxidant activity than the wild-type yeast cytochrome c and (ii), like the yeast cytochrome c, inactive in caspase stimulation, even if added in 400-fold excess compared with the horse protein. Thus this mutant seems to be a good candidate for knock-in studies of the role of cytochrome c-mediated apoptosis, in contrast with the horse K72R, K72G, K72L and K72A mutant cytochromes that at low concentrations were less active in apoptosis than the wild-type, but were quite active when the concentrations were increased by a factor of 2–12.

scholarly journals Electron Transfer and Binding of thec-Type Cytochrome TorC to the TrimethylamineN-Oxide Reductase inEscherichia coli

2000 ◽  
Vol 276 (15) ◽  
pp. 11545-11551 ◽  
Author(s):  
Stéphanie Gon ◽  
Marie-Thérèse Giudici-Orticoni ◽  
Vincent Méjean ◽  
Chantal Iobbi-Nivol
Keyword(s):  
Electron Transfer ◽  
Biochemical Characterization ◽  
Reduced Form ◽  
Visible Absorption ◽  
Midpoint Potential ◽  
Redox Potentiometry ◽  
Family Based ◽  
Transfer Chain

Reduction of trimethylamineN-oxide (E′0(TMAO/TMA)= +130 mV) inEscherichia coliis carried out by the Tor system, an electron transfer chain encoded by thetorCADoperon and made up of the periplasmic terminal reductase TorA and the membrane-anchored pentahemicc-type cytochrome TorC. Although the role of TorA in the reduction of trimethylamineN-oxide (TMAO) has been clearly established, no direct evidence for TorC involvement has been presented. TorC belongs to the NirT/NapCc-type cytochrome family based on homologies of its N-terminal tetrahemic domain (TorCN) to the cytochromes of this family, but TorC contains a C-terminal extension (TorCC) with an additional heme-binding site. In this study, we show that both domains are required for the anaerobic bacterial growth with TMAO. The intact TorC protein and its two domains, TorCNand TorCC, were produced independently and purified for a biochemical characterization. The reduced form of TorC exhibited visible absorption maxima at 552, 523, and 417 nm. Mediated redox potentiometry of the heme centers of the purified components identified two negative midpoint potentials (−177 and −98 mV) localized in the tetrahemic TorCNand one positive midpoint potential (+120 mV) in the monohemic TorCC. In agreement with these values, thein vitroreconstitution of electron transfer between TorC, TorCN, or TorCCand TorA showed that only TorC and TorCCwere capable of electron transfer to TorA. Surprisingly, interaction studies revealed that only TorC and TorCNstrongly bind TorA. Therefore, TorCCdirectly transfers electrons to TorA, whereas TorCN, which probably receives electrons from the menaquinone pool, is involved in both the electron transfer to TorCCand the binding to TorA.

scholarly journals Activation of 3-Mercaptopyruvate Sulfurtransferase by Glutaredoxin Reducing System

Biomolecules ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 826
Author(s):  
Noriyuki Nagahara
Keyword(s):  
Oxidative Stress ◽  
Electron Transfer ◽  
Glutathione Reductase ◽  
Nicotinamide Adenine Dinucleotide ◽  
Transfer Reaction ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Electron Transfer Reaction ◽  
Reduced Form ◽  
Mercaptopyruvate Sulfurtransferase ◽  
Substrate Proteins

Glutaredoxin (EC 1.15–1.21) is known as an oxidoreductase that protects cysteine residues within proteins against oxidative stress. Glutaredoxin catalyzes an electron transfer reaction that donates an electron to substrate proteins in the reducing system composed of glutaredoxin, glutathione, glutathione reductase, and nicotinamide-adenine dinucleotide phosphate (reduced form). 3-mercaptopyruvate sulfurtransferase (EC 2.8.1.2) is a cysteine enzyme that catalyzes transsulfuration, and glutaredoxin activates 3-mercaptopyruvate sulfurtransferase in the reducing system. Interestingly, even when glutathione or glutathione reductase was absent, 3-mercaptopyruvate sulfurtransferase activity increased, probably because reduced glutaredoxin was partly present and able to activate 3-mercaptopyruvate sulfurtransferase until depletion. A study using mutant Escherichia coli glutaredoxin1 (Cys14 is the binding site of glutathione and was replaced with a Ser residue) confirmed these results. Some inconsistency was noted, and glutaredoxin with higher redox potential than either 3-mercaptopyruvate sulfurtransferase or glutathione reduced 3-mercaptopyruvate sulfurtransferase. However, electron-transfer enzymatically proceeded from glutaredoxin to 3-mercaptopyruvate sulfurtransferase.

scholarly journals The redox potentials of the two-iron plant algal ferredoxins. An electrostatic model

1973 ◽  
Vol 133 (2) ◽  
pp. 283-287 ◽  
Author(s):  
R. J. Kassner ◽  
W. Yang
Keyword(s):  
Electron Transfer ◽  
Free Energy ◽  
Redox Potential ◽  
Negative Charge ◽  
Electrostatic Model ◽  
Redox Potentials ◽  
Electron Transfer Proteins ◽  
Electrostatic Free Energy ◽  
The One ◽  
Charged Ions

The two-iron–sulphur co-ordination centre in plant and algal ferredoxins is considered as a collection of charged ions whose net negative charge is twice that of the one-iron–sulphur protein rubredoxin. Calculation of the electrostatic free-energy changes for reduction of the two types of proteins indicates that the redox potential of the two-iron–sulphur proteins should be more negative than that of the one-iron–sulphur protein and that in biological systems the ferredoxins should function as one-electron transfer proteins.

Molecular Mechanism of the Electron Transfer Reaction in Cytochrome P450cam−Putidaredoxin:  Roles of Glutamine 360 at the Heme Proximal Site†

Biochemistry ◽  
2002 ◽  
Vol 41 (47) ◽  
pp. 13883-13893 ◽  
Author(s):  
Takehiko Tosha ◽  
Shiro Yoshioka ◽  
Hiroshi Hori ◽  
Satoshi Takahashi ◽  
Koichiro Ishimori ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Molecular Mechanism ◽  
Transfer Reaction ◽  
Electron Transfer Reaction ◽  
Cytochrome P450cam ◽  
Proximal Site
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