The influence of pH on the rates of enzyme reactions. Part 5.—The case of several enzyme-substrate intermediates

1960 ◽  
Vol 56 (0) ◽  
pp. 1467-1476 ◽  
Author(s):  
Richard M. Krupka ◽  
K. J. Laidler
Keyword(s):  
Enzyme Reactions ◽  
Enzyme Substrate ◽  
Influence Of Ph

The influence of pH and inhibitors on the kinetics of enzyme reactions involving two intermediates

1967 ◽  
Vol 45 (5) ◽  
pp. 539-546 ◽  
Author(s):  
Harvey Kaplan ◽  
Keith J. Laidler
Keyword(s):  
Steady State ◽  
Ph Dependence ◽  
Free Enzyme ◽  
State Equations ◽  
Enzyme Reactions ◽  
Substrate Complex ◽  
Rate Determining Step ◽  
Enzyme Substrate ◽  
Special Cases ◽  
Influence Of Ph

General steady-state equations are worked out for enzyme reactions which occur according to the scheme [Formula: see text]Equations showing the pH dependence of the kinetic parameters are developed in a form which distinguishes between essential and nonessential ionizing groups. The pK dependence of [Formula: see text], the second-order constant extrapolated to zero substrate constant, gives pK values for groups which ionize on the free enzyme, but reveals such a pK only if the corresponding group is also involved in the breakdown of the Michaelis complex. General steady-state equations are also developed for the case in which an inhibitor can combine with the free enzyme, the enzyme–substrate complex, and also a second intermediate (e.g. an acyl enzyme). The equations are given in a form that is convenient for analyzing the experimental results, and a number of special cases are considered. It is shown how the type of inhibition depends not only on the nature of the inhibitor but also on that of the substrate, an important factor being the rate-determining step of the reaction. Examples of the various kinds of behavior are given.

Final Phase of Enzyme Reactions Following a Michaelis-Menten Mechanism in which the Free Enzyme and/or the Enzyme-Substrate Complex are Unstable

1994 ◽  
Vol 375 (1) ◽  
pp. 35-42 ◽  
Author(s):  
Ramón Varón ◽  
Carmelo Garrido del Solo ◽  
Manuela Garcίa-Moreno ◽  
Angela Sánchez-Gracia ◽  
Francisco Garcίa-Cánovas
Keyword(s):  
Free Enzyme ◽  
Final Phase ◽  
Enzyme Reactions ◽  
Substrate Complex ◽  
Enzyme Substrate

THE INFLUENCE OF pH ON THE HYDROLYSIS OF BENZOYLCHOLINE BY PSEUDOCHOLINESTERASE OF HUMAN PLASMA

1964 ◽  
Vol 42 (2) ◽  
pp. 161-168 ◽  
Author(s):  
W. Kalow
Keyword(s):  
Human Plasma ◽  
Binding Sites ◽  
Dissociation Constants ◽  
Enzyme Molecule ◽  
Acid Base ◽  
Enzyme Substrate ◽  
Michaelis Constants ◽  
Automatic Titrator ◽  
Influence Of Ph ◽  
Hydrolysis Of

The study was performed with an automatic titrator and purified human pseudocholinesterase prepared from pooled plasma. The data obtained are compatible with the assumption that each enzyme molecule contains two binding sites for benzoylcholine which are unlike in their dependence on pH. Michaelis constants and maximum hydrolysis velocities were derived for each of the two binding sites, and acid–base dissociation constants of the enzyme substrate complexes were estimated.

Accounting for the instantaneous disorder in the enzyme-substrate Michaelis complex to calculate the Gibbs free energy barrier of an enzyme reaction

2021 ◽  
Author(s):  
Sonia Romero-Téllez ◽  
Alejandro Cruz ◽  
Laura Masgrau ◽  
Àngels González-Lafont ◽  
José M Lluch
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Energy Barrier ◽  
Enzyme Reaction ◽  
Free Energy Barrier ◽  
Wide Spread ◽  
Energy Barriers ◽  
Enzyme Reactions ◽  
Enzyme Substrate

Many enzyme reactions present instantaneous disorder. These dynamic fluctuations in the enzyme-substrate Michaelis complexes generate a wide spread of energy barriers that cannot be experimentally observed, but that determines the...

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