Kinetics of Abiotic Hydrolysis of Isoxaflutole:  Influence of pH and Temperature in Aqueous Mineral Buffered Solutions

2000 ◽  
Vol 48 (9) ◽  
pp. 4399-4403 ◽  
Author(s):  
E. Beltran ◽  
H. Fenet ◽  
J. F. Cooper ◽  
C. M. Coste
Keyword(s):  
Influence Of Ph ◽  
Kinetics Of ◽  
Hydrolysis Of

THE TRYPSIN CATALYZED HYDROLYSIS OF p-NITROPHENYL ACETATE

1959 ◽  
Vol 37 (4) ◽  
pp. 751-759 ◽  
Author(s):  
James A. Stewart ◽  
Ludovic Ouellet
Keyword(s):  
Active Site ◽  
Initial Rate ◽  
Competitive Inhibition ◽  
Early Stage ◽  
Stopped Flow ◽  
Hydrogen Ions ◽  
Experimental Conditions ◽  
Influence Of Ph ◽  
Kinetics Of ◽  
Hydrolysis Of

The hydrolysis of p-nitrophenyl acetate (NPA) by trypsin has been investigated in the early stage of the reaction using stopped-flow techniques. The influence of pH on the initial rate suggests competitive inhibition of the active site of the enzyme by hydrogen ions. The dissociation constant of the enzyme obtained from the kinetics of this reaction (pK = 6.9) indicates possible catalysis by an ammo group or an imidazole group of the enzyme. Lysine methyl ester as an analogue of the enzyme catalyzes the hydrolysis of NPA under similar experimental conditions. The results are described in terms of an assumed mechanism and the nature of the catalytic site is discussed.

Kinetics of α-chymotrypsin action. I. pH, solvent, and temperature effects

1967 ◽  
Vol 45 (5) ◽  
pp. 547-557 ◽  
Author(s):  
Harvey Kaplan ◽  
K. J. Laidler
Keyword(s):  
Dielectric Constant ◽  
Low Temperature ◽  
Temperature Effects ◽  
Methyl Esters ◽  
The Other ◽  
Kcal Mole ◽  
Influence Of Ph ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Ph Variations

An investigation has been made of the influence of pH on the kinetics of the α-chymotrypsin-catalyzed hydrolysis of N-acetyl-l-tyrosine ethyl ester, p-nitrophenyl acetate, and N-benzoyl-d- and -l-alanine methyl esters. From the pH variations of [Formula: see text], and [Formula: see text], it is deduced that in the free enzyme there are ionizing groups of pK 6.9 and 9.2. From the variation of these pK values with dielectric constant, it is concluded that, when protonated, one group is cationic and the other neutral. A temperature-dependence study was carried out on N–benzoyl-d- and -l-alanine methyl esters. The sharp break in the plot of log [Formula: see text] against 1/T is attributed to a rapid reversible denaturation of the enzyme at the higher temperatures. In the low-temperature region, the activation energies are ΔEL = 16.2 ± 0.3 kcal/mole and ΔED = 16.5 ± 0.6 kcal/mole.

Influence of pH on the Kinetics of Reactions Catalyzed by Alkaline Phosphatase

1973 ◽  
Vol 51 (7) ◽  
pp. 1096-1103 ◽  
Author(s):  
Irwin Hinberg ◽  
Keith J. Laidler
Keyword(s):  
Alkaline Phosphatase ◽  
Intestinal Alkaline Phosphatase ◽  
Nitrophenyl Phosphate ◽  
Wide Range ◽  
Coordinated Water ◽  
Ph Range ◽  
Barbital Buffer ◽  
Influence Of Ph ◽  
Kinetics Of ◽  
Hydrolysis Of

An experimental study has been made of the kinetics of the hydrolysis of p-nitrophenyl phosphate catalyzed by chicken-intestinal alkaline phosphatase. The work was done in barbital buffer (carbonate above pH 9.6), and covered the pH range from 7.0 to 10.0. A sufficiently wide range of substrate concentration was used to allow reliable values of [Formula: see text] and [Formula: see text] to be determined. The results lead to pK values of 8.1 and 8.6 for the free enzyme, and it is concluded that the Michaelis complex and the phosphoryl intermediate ionize only on the acid side, the former also having a pK of 8.1. It is suggested that the group of pK 8.1 is probably an α-amino group and that the group of pK 8.6 probably corresponds to the ionization of a Zn(II)-coordinated water molecule.

THE INFLUENCE of pH ON the KINETICS of ACID HYDROLYSIS of SUCROSE

1994 ◽  
Vol 17 (2) ◽  
pp. 191-208 ◽  
Author(s):  
A. PINHEIRO TORRES ◽  
F.A.R. OLIVEIRA ◽  
C.L.M. SILVA ◽  
S.P. FORTUNA
Keyword(s):  
Acid Hydrolysis ◽  
Influence Of Ph ◽  
Kinetics Of ◽  
Hydrolysis Of

Influence of enzymes, pH and temperature on the kinetics of whey protein hydrolysis / Influencia de los enzimas, pH y temperatura en la cinética de la hidrólisis de las proteínas del lactosuero

1998 ◽  
Vol 4 (2) ◽  
pp. 79-84 ◽  
Author(s):  
F. Camacho ◽  
P. González-Tello ◽  
E.M. Guadix
Keyword(s):  
Operating Temperature ◽  
Whey Proteins ◽  
Salt Content ◽  
Optimum Operating ◽  
Degree Of Hydrolysis ◽  
Optimum Operating Temperature ◽  
Special Diets ◽  
Influence Of Ph ◽  
Kinetics Of ◽  
Hydrolysis Of

The influence of pH, temperature and the mixture of enzymes (MKC Protease 660 L and PEM 2500 S) on the enzymatic hydrolysis of whey proteins was studied. The experiments show that all results were reproducible via a kinetic model that supposes the rapid and irreversible binding of part of the proteases to an inhibitor in the substrate, followed by a zero-order hydrolysis with respect to the substrate which occurs simultaneously with a second order enzymatic denatural ization produced by an attack of the free proteases upon those bound to the substrate-enzyme complex. Use of the optimum operating temperature of 60 °C and pH 8-10 led to a greater degree of hydrolysis. However, increasing the pH to these levels means that the salt content, on neutral izing the hydrolysate, is somewhat high and this is often unsuitable for the preparation of special diets. In the experiments performed with mixtures of enzymes, two contrasting phenomena occurred; there appears to be synergism between the proteases, which is preceded by a loss in enzymatic activity greater than that which can be accounted for by the presence of the inhibitor in the whey proteins.

Influence of medium on alkaline hydrolysis of succinic acid monomethyl and monopropyl esters

1980 ◽  
Vol 45 (11) ◽  
pp. 2873-2882
Author(s):  
Vladislav Holba ◽  
Ján Benko
Keyword(s):  
Succinic Acid ◽  
Kinetic Parameters ◽  
Alkaline Hydrolysis ◽  
Specific Interactions ◽  
Nonaqueous Media ◽  
The Media ◽  
Kinetics Of ◽  
Hydrolysis Of

The kinetics of alkaline hydrolysis of succinic acid monomethyl and monopropyl esters were studied in mixed aqueous-nonaqueous media at various temperatures and ionic strengths. The results of measurements are discussed in terms of electrostatic and specific interactions between the reactants and other components of the reaction mixture. The kinetic parameters in the media under study are related to the influence of the cosolvent on the solvation sphere of the reactants.

Belousov–Zhabotinskii type oscillation reaction with glycerol and kinetics of reactions between the system components

1987 ◽  
Vol 52 (10) ◽  
pp. 2375-2382 ◽  
Author(s):  
Ľubica Adamčíková ◽  
Peter Ševčík
Keyword(s):  
Oscillation System ◽  
Chemical Oscillations ◽  
Oscillation Reaction ◽  
Reaction Solution ◽  
System Components ◽  
Probable Source ◽  
Belousov Zhabotinskii Reaction ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Type Oscillation

Glycerol causes chemical oscillations in Belousov-Zhabotinskii reaction in a closed system as well as in a reaction solution bubbled with nitrogen. Since the oxidation of glycerol with bromate ions does not proceed autocatalytically and bromine in the oxidation state 0 or +1 in the absence of light does not react with glycerol, hydrolysis of bromine is the probable source of bromide ions in the studied oscillation system.

Kinetics of hydrolysis of peroxodisulphate ions in acidic medium to peroxomonosulphuric acid

1981 ◽  
Vol 46 (5) ◽  
pp. 1229-1236 ◽  
Author(s):  
Jan Balej ◽  
Milada Thumová
Keyword(s):  
Ionic Strength ◽  
Rate Constants ◽  
Acidic Medium ◽  
Measured Data ◽  
Molar Ratios ◽  
Starting Solution ◽  
Kinetics Of Hydrolysis ◽  
Rate Of Hydrolysis ◽  
Kinetics Of ◽  
Hydrolysis Of

The rate of hydrolysis of S2O82- ions in acidic medium to peroxomonosulphuric acid was measured at 20 and 30 °C. The composition of the starting solution corresponded to the anolyte flowing out from an electrolyser for production of this acid or its ammonium salt at various degrees of conversion and starting molar ratios of sulphuric acid to ammonium sulphate. The measured data served to calculate the rate constants at both temperatures on the basis of the earlier proposed mechanism of the hydrolysis, and their dependence on the ionic strength was studied.

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