Co-solvent effects on reaction rate and reaction equilibrium of an enzymatic peptide hydrolysis

2018 ◽  
Vol 20 (16) ◽  
pp. 11317-11326 ◽  
Author(s):  
A. Wangler ◽  
R. Canales ◽  
C. Held ◽  
T. Q. Luong ◽  
R. Winter ◽  
...  
Keyword(s):  
Equilibrium Constant ◽  
Solvent Effects ◽  
Reaction Rate ◽  
Peptide Hydrolysis ◽  
Michaelis Constant ◽  
Thermodynamic Activities ◽  
Reaction Equilibrium

This work presents an approach that expresses the Michaelis constant KaM and the equilibrium constant Kth of an enzymatic peptide hydrolysis based on thermodynamic activities instead of concentrations.

Kinetik und Mechanismus der enzymatischen Dextransynthese und Wirkung der Akzeptoren auf diese Reaktion

1968 ◽  
Vol 23 (6) ◽  
pp. 788-797 ◽  
Author(s):  
K. H. Ebert ◽  
G. Schenk
Keyword(s):  
Reaction Rate ◽  
Polymer Chains ◽  
Low Molecular Weight ◽  
Michaelis Constant ◽  
Acceptor Reaction ◽  
General Applicability ◽  
Polymer Molecules ◽  
Molecular Weights ◽  
Reaction Constants ◽  
Good Agreement

According to the proposed mechanism, the enzymic formation of dextran from sucrose consists of two reaction steps: the propagation reaction forming polymer molecules by an insertion type growth, and the acceptor reaction leading to the termination of the polymer chains. This mechanism is of a more general applicability; it explains hydrolysis, transfer and poly reactions.A complete kinetic analysis is given for the dextran formation and values for the reaction constants Vm, Km and Ka (the Michaelis constant of the acceptor reaction) have been evaluated. Very good agreement between the rate data calculated from the mechanism and the experimental data has been obtained.From experiments with a series of radioactively labelled acceptors it was established that the acceptor reaction, in fact, proceeds as proposed by the mechanism. Further, it was found that strong acceptors, leading to the formation of low molecular weight dextrans, do not inhibit the reaction rate, and that weak acceptors, which inhibit the reaction rate, have only a small effect on the molecular weights. This correlation has also been demonstrated in terms of the proposed reaction mechanism.

INHIBITION AND ACTIVATION OF ADENYLOSUCCINIC SYNTHETASE BY 8-AZAGUANOSINE TRIPHOSPHATE

1963 ◽  
Vol 41 (1) ◽  
pp. 1495-1501 ◽  
Author(s):  
L. H. Cohen ◽  
R. E. Parks Jr.
Keyword(s):  
Reaction Rate ◽  
Maximal Velocity ◽  
Michaelis Constant ◽  
High Concentrations

8-Azaguanosine triphosphate can function in place of GTP in the reaction catalyzed by adenylosuccinic synthetase. The Michaelis constant and maximal velocity for the reaction obtained with the analogue are lower than those obtained with GTP. As a result, 8-azaGTP increases the reaction rate at low GTP concentrations and inhibits competitively at high GTP concentrations. It is suggested that this type of inhibition might be exploited in the development of chemo-therapeutic analogues specific for tissues containing high concentrations of a coenzyme or metabolite.

scholarly journals The temperature-dependence of adenylate cyclase from baker's yeast

1979 ◽  
Vol 181 (3) ◽  
pp. 539-543 ◽  
Author(s):  
J Londesborough ◽  
K Varimo
Keyword(s):  
Reaction Mechanism ◽  
Adenylate Cyclase ◽  
Temperature Dependence ◽  
Reaction Rate ◽  
Arrhenius Plot ◽  
Maximum Velocity ◽  
Michaelis Constant ◽  
Arrhenius Plots ◽  
Temperature Range ◽  
Membrane Bound

The Michaelis constant of membrane-bound adenylate cyclase increased from 1.1 to 1.8 mM between 7 and 38 degrees C (delta H = 13 kJ/mol). Over this temperature range, the maximum velocity increased 10-fold, and the Arrhenius plot was nearly linear, with an average delta H* of 51 kJ/mol. The temperature-dependence of the reaction rate at 2 mM-ATP was examined in more detail: for Lubrol-dispersed enzyme, Arrhenius plots were nearly linear with average delta H* values of 45 and 68 kJ/mol, respectively, for untreated and gel-filtered enzymes; for membrane-bound enzyme, delta H changed from 40 kJ/mol above about 21 degrees C to 62 kJ/mol below 21 degrees C, but this behaviour does not necessarily indicate an abrupt, lipid-induced, transition in the reaction mechanism.

Inverse solvent effects in the heterogeneous and homogeneous epoxidation of cis-2-heptene with [2-percarboxyethyl]-functionalized silica and meta-chloroperbenzoic acid

2014 ◽  
Vol 12 (20) ◽  
pp. 3246-3250 ◽  
Author(s):  
Rossella Mello ◽  
Jeymy T. Sarmiento-Monsalve ◽  
Diana Vargas-Oviedo ◽  
Rafael Acerete ◽  
María Elena González-Núñez ◽  
...  
Keyword(s):  
Solid Surface ◽  
Solvent Effects ◽  
Reaction Rate ◽  
Functionalized Silica ◽  
Solvent Layer

The organized solvent layer on the solid surface determines the reaction rate in the heterogeneous epoxidation of cis-2-heptene.

The Photochemically Produced Ketyl of Perfluorobenzophenone: Electron Spin Resonance Studies of Solvent Effects

1973 ◽  
Vol 51 (19) ◽  
pp. 3211-3216 ◽  
Author(s):  
Frederick Peter Sargent ◽  
Marshall Grant Bailey
Keyword(s):  
Electron Spin Resonance ◽  
Equilibrium Constant ◽  
Mole Fraction ◽  
Electron Spin ◽  
Solvent Effects ◽  
Chemical Exchange ◽  
Solvent Molecule ◽  
Solvent Mixtures ◽  
Ketyl Radical ◽  
Spin Resonance

The ketyl radical is formed when solutions of perfluorobenzophenone are photolyzed with u.v. light. The radical was identified by electron spin resonance (e.s.r.) studies of the effects of solvent, temperature, chemical exchange, and deuteration on the spectra. Solvent mixtures of cyclohexane and ethanol gave spectra which were very sensitive to the mole fraction of alcohol in the range 0–1%. An equilibrium constant for solvent molecule exchange has been deduced.

scholarly journals Water Activity Regulates CO2 Reduction in Gas-Diffusion Electrodes

2021 ◽  
Author(s):  
Nathan Nesbitt ◽  
Wilson Smith
Keyword(s):  
Gas Phase ◽  
Paradigm Shift ◽  
Reaction Rate ◽  
Co2 Reduction ◽  
Gas Diffusion ◽  
Equilibrium Potential ◽  
Gas Diffusion Electrodes ◽  
Reaction Thermodynamics ◽  
Current Densities ◽  
Reaction Equilibrium

<p>Electrochemical CO<sub>2</sub> reduction has recently reached current densities as high as 1 A cm<sup>-2</sup>, enabled by improving diffusion of CO<sub>2</sub> from the gas phase to the electrocatalyst by use of gas-diffusion electrodes (GDEs) and by improving electrolyte ionic conductivity with concentrated hydroxide electrolytes (7 M KOH). Despite such high solute concentrations, the dilute electrolyte assumption is commonly used to evaluate the thermodynamics of the system, specifically reaction equilibrium potential and reaction rate expression. Here we establish a paradigm shift by demonstrating how to properly include the activity of water and solutes and highlighting corrections to associated reaction thermodynamics.</p>

scholarly journals Study of the kinetics of Bombyx mori chitosan ascorbate formation

2020 ◽  
Vol 99 (3) ◽  
pp. 38-43
Author(s):  
K.K. Pirniyazov ◽  
◽  
S.Sh. Rashidova ◽  
Keyword(s):  
Activation Energy ◽  
Ascorbic Acid ◽  
Bombyx Mori ◽  
Equilibrium Constant ◽  
Reaction Rate ◽  
Reaction Order ◽  
Average Rate ◽  
Kinetic Studies ◽  
Water Soluble ◽  
The One

In this work, for the first time, a water-soluble natural biopolymer of chitosan ascorbate based on Bombyx mori chitosan and ascorbic acid was obtained and kinetic features of the process were determined. Samples of chitosan ascorbate were synthesized, the interaction of chitosan with ascorbic acid was studied by analytical titration. The synthesis was carried out in order to determine the activation energy of formation of the reaction of chitosan ascorbate, in the ratio of chitosan and ascorbic acid (4:1) components for 15 minutes with a reaction temperature ranging from 25°C to 65°C. The results of the kinetic studies show that in the interaction under the study the reaction order on ascorbic acid concentration exceeds the reaction order on chitosan concentration, while the reaction activation energy was determined, which equals to 13.38 kJ/mol. This result allows us to conclude that during the formation of chitosan ascorbate at 55 °C the highest equilibrium constant is established, and a further increase in temperature leads to a decrease in the yield and equilibrium constant. The results obtained indicate that with an increase in the concentration of ascorbic acid compared to the one of chitosan, the reaction rate increased almost twice. It was found that with an increase in the reaction time, the average rate of synthesis gradually decreases. This is due to the fact that with an increase in the duration of the reaction in the solution the concentration of unbound (free) ascorbic acid decreases, and as a result, the reaction rate decreases as well.

scholarly journals REACTION KINETICS OF Cu ELECTRO-DEPOSITION ON THE SURFACE OF TiO2/GRAPHITE

2015 ◽  
Vol 8 (2) ◽  
pp. 116
Author(s):  
Fitria Rahmawati ◽  
Wanodya Anggit Mawasthi ◽  
Patiha
Keyword(s):  
Equilibrium Constant ◽  
Rate Constant ◽  
Reaction Rate ◽  
Reaction Order ◽  
Electrode Reaction ◽  
Deposition Process ◽  
Anodic Reaction ◽  
Electro Deposition ◽  
First Order ◽  
Kinetics Of

Research on the kinetics of electrode reaction during copper electro-deposition on the surface of TiO2/graphite has been conducted. The aims of this research are to determine the ratio of anodic reaction rate to cathodic reaction rate , the ratio of anodic rate constant to cathodic rate constant , the equilibrium constant when the reaction reach equilibrium condition and to study the polarization in the electro-deposition reaction. Copper was deposited electrochemically from CuSO4 solution at various concentration i.e. 0.1 M; 0.2 M; 0.3 M; 0.4 M; 0.5 M. In every 5 minutes during electro-deposition process, the pH changes in anode cell was recorded and the change of Cu2+ concentration was also analyzed by spectrophotometric method. The result shows that the reaction order of Cu2+ reduction is first order and the oxidation of H2O in anodic cell is zero order. The ratio of anodic rate constant to cathodic rate constant, is 4.589´10-3 ± 0.071´10‑3. It indicates that the reaction rate  in cathode is larger than the reaction rate in anode and it allowed polarization.  The electrochemical cell reached equilibrium after 25 minutes with the equilibrium constant is 8.188´10-10 ± 1.628´10-10.

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