scholarly journals Kinetics of protein-modification reactions. Stoichiometry of modification-produced enzyme inactivation: modification of rhodanese by 2,4,6-trinitrobenzenesulphonic acid

1985 ◽  
Vol 230 (1) ◽  
pp. 89-93 ◽  
Author(s):  
E T Rakitzis ◽  
T B Malliopoulou
Keyword(s):  
Protein Modification ◽  
Reaction Medium ◽  
Enzyme Inactivation ◽  
Mathematical Treatment ◽  
Modifying Agent ◽  
Catalytic Function ◽  
Reactive Groups ◽  
Decreasing Ph ◽  
Activity Loss ◽  
Kinetics Of

A mathematical treatment is presented for the dependence of enzyme activity loss on the numbers and reactivities of the groups essential for catalytic function, when enzyme protein modification is carried out by the use of concentrations of protein reactive groups well in excess of that of modifying agent. Experimentally obtained data on the modification of rhodanese (thiosulphate sulphurtransferase, EC 2.8.1.1) by 2,4,6-trinitrobenzenesulphonic acid are presented, and it is shown that, at pH9.00, the fractional concentration of rhodanese groups, or of rhodanese group reactivities, essential for enzyme catalytic function is 0.88; this value is found to decrease with decreasing pH of the reaction medium. The possibility that rhodanese inactivation by 2,4,6-trinitrobenzenesulphonic acid is brought about by modification of groups other than amino groups is ruled out by a comparison of the enzyme-inactivation and protein-modification stoichiometries, for putative reaction models for enzyme and modifying agent.

scholarly journals Kinetics of protein-modification reactions. Determination of the fractional concentration of enzyme protein groups, or group reactivities, essential for catalytic function

1986 ◽  
Vol 237 (2) ◽  
pp. 589-591 ◽  
Author(s):  
E T Rakitzis ◽  
T B Malliopoulou
Keyword(s):  
Protein Modification ◽  
Initial Reaction ◽  
Mathematical Treatment ◽  
Enzyme Protein ◽  
First Derivative ◽  
Catalytic Function ◽  
Fractional Concentration ◽  
Reactive Groups ◽  
Activity Loss

A mathematical treatment of modification-induced enzyme protein inactivation is presented, and it is shown that, at initial reaction conditions, the ratio of the first derivative of the equation describing enzyme activity loss to the first derivative of the equation describing protein groups modification is equal to the fractional concentration of enzyme protein reactive groups, or group reactivities, essential for catalytic function.

scholarly journals Kinetics of irreversible enzyme inhibition by an unstable inhibitor

1974 ◽  
Vol 141 (2) ◽  
pp. 601-603 ◽  
Author(s):  
Emmanuel T. Rakitzis
Keyword(s):  
Methyl Ester ◽  
Enzyme Inhibition ◽  
Cathepsin D ◽  
Fluorescein Isothiocyanate ◽  
Order Reaction ◽  
Enzyme Inactivation ◽  
First Order Reaction ◽  
Mathematical Treatment ◽  
First Order ◽  
Kinetics Of

A mathematical treatment for the general case of enzyme inactivation by an inhibitor that breaks down in solution in a first-order reaction is presented. Cathepsin D was inactivated by fluorescein isothiocyanate with a Ki of 4.47μm. Kinetic constants were also determined for the inactivation of cathepsin D by 1,1-bis(diazoacetyl)-2-phenylethane, and the inactivation of pepsin C by diazoacetyl-dl-norleucine methyl ester.

Polymer structure and catalytic activity of ion exchangers

1981 ◽  
Vol 46 (7) ◽  
pp. 1577-1587 ◽  
Author(s):  
Karel Jeřábek
Keyword(s):  
Catalytic Activity ◽  
Ethyl Acetate ◽  
Active Sites ◽  
Crosslinking Agent ◽  
Reaction Medium ◽  
Polymer Structure ◽  
Local Concentration ◽  
Ion Exchangers ◽  
Styrene Divinylbenzene ◽  
Kinetics Of

Catalytic activity of ion exchangers prepared by partial sulphonation of styrene-divinylbenzene copolymers in reesterifications of ethyl acetate by methanol and propanol, hydrolysis of ethyl acetate and in synthesis of bisphenol A has been compared with data on polymer structure of these catalysts and with distribution of the crosslinking agent, divinylbenzene, calculated from literature data on kinetics of copolymerisation of styrene with divinylbenzene. It was found that the polymer structure of ion exchangers influences catalytic activity predominantly by changing the local concentration of acid active sites. The results obtained indicated that the effect of transport phenomena on the rate of catalytic reactions does not depend on the degree of swelling of the ion exchangers in reaction medium but it is mainly dependent on the relative affinity of reaction components to the acid groups or to the polymer skeleton.

scholarly journals Thermodynamic and detailed kinetic study of the formation of orthophthalaldehyde-agmatine complex by fluorescence intensities

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Khémesse Kital ◽  
Moumouny Traoré ◽  
Diégane Sarr ◽  
Moussa Mbaye ◽  
Mame Diabou Gaye Seye ◽  
...  
Keyword(s):  
Complex Formation ◽  
Thermodynamic Parameters ◽  
Initial Rate ◽  
Reaction Medium ◽  
Standard Entropy ◽  
Step Size ◽  
Formation Reaction ◽  
Different Temperatures ◽  
Kinetics Of ◽  
Complex Formation Process

Abstract The aim of this work is to determine the thermodynamic parameters and the kinetics of complex formation between orthophthalaldehyde (OPA) and agmatine (AGM) in an alkaline medium (pH 13). Firstly, the association constant (Ka) between orthophthalaldehyde and agmatine was determined at different temperatures (between 298 K and 338 K) with a step size of 10 K. Secondly, the thermodynamic parameters such as standard enthalpy (ΔH°), standard entropy (ΔS°),and Gibbs energy (∆G) were calculated, where a positive value of ΔH° (+45.50 kJ/mol) was found, which shows that the reaction is endothermic. In addition, the low value of ΔS°(+0.24 kJ/mol) indicates a slight increase in the disorder in the reaction medium. Furthermore, the negative values of ΔG between −35.62 kJ/mol and −26.02 kJ/mol show that the complex formation process is spontaneous. Finally, the parameters of the kinetics of the reaction between OPA and AGM were determined as follows: when the initial concentration of AGM (5 × 10−6 M) is equal to that of the OPA, the results show that the reaction follows an overall 1.5 order kinetics with an initial rate of 5.1 × 10−7Mmin−1 and a half-life of 8.12 min. The partial order found in relation to the AGM is 0.8. This work shows that the excess of OPA accelerates the formation reaction of the complex.

Sign in / Sign up

Export Citation Format

Share Document