Transient-Phase and Steady-State Kinetics for Inhibited Enzyme Systems. II. Double-Intermediate Mechanisms

1973 ◽  
Vol 51 (6) ◽  
pp. 822-831 ◽  
Author(s):  
Nasrat H. Hijazi ◽  
Keith J. Laidler
Keyword(s):  
Steady State ◽  
Rate Constants ◽  
Enzyme Concentration ◽  
Transient Phase ◽  
Enzyme Systems ◽  
Steady State Kinetics ◽  
Inhibited Enzyme

Equations for the pre-steady state and the steady state are derived for enzyme systems in which the enzyme E, the substrate A, and an inhibitor Q are present together, the enzyme concentration being much lower than the concentrations of A and Q. Various mechanisms are considered, ail of them involving two intermediates EA and EA′ (e.g. an acyl enzyme). When the inhibition is reversible the transient phase is followed by the establishment of a steady state. It is shown how experimental pre-steady-state and steady-state results can be analyzed to obtain rate constants, including those for the binding of inhibitor. If the binding of inhibitor is irreversible there is no steady state.

Transient-Phase and Steady-State Kinetics for Inhibited Enzyme Systems. I. Single-Intermediate Mechanisms

1973 ◽  
Vol 51 (6) ◽  
pp. 815-821 ◽  
Author(s):  
Nasrat H. Hijazi ◽  
Keith J. Laidler
Keyword(s):  
Steady State ◽  
Enzyme Concentration ◽  
Experimental Results ◽  
Transient Phase ◽  
Steady State Analysis ◽  
Noncompetitive Inhibition ◽  
Enzyme Systems ◽  
Steady State Kinetics ◽  
Inhibited Enzyme ◽  
State Analysis

Equations for the pre-steady state and the steady state are derived for enzyme systems in which enzyme E, substrate A, and inhibitor Q are present, the enzyme concentration being lower than the substrate and inhibitor concentrations. It is assumed that the mechanism involves a single intermediate EA. Equations for competitive, anticompetitive, and pure noncompetitive inhibition are derived. When the inhibition is reversible the transient phase is followed by the establishment of a steady state. Analysis of experimental results is discussed for each type of inhibition. If the inhibition is irreversible, there is no steady state.

Transient-Phase and Steady-State Kinetics for Enzyme Systems Involving Two Substrates

1973 ◽  
Vol 51 (6) ◽  
pp. 832-840 ◽  
Author(s):  
Nasrat H. Hijazi ◽  
Keith J. Laidler
Keyword(s):  
Steady State ◽  
Ternary Complex ◽  
Transient Phase ◽  
Complex Mechanism ◽  
State Equations ◽  
Enzyme Systems ◽  
Steady State Kinetics ◽  
Ping Pong ◽  
The Individual ◽  
Individual Rate

The transient-phase and steady-state equations are derived for four enzyme mechanisms involving two substrates, namely (1) Theorell–Chance mechanism, (2) ping pong bi bi mechanism, (3) ordered ternary-complex mechanism, and (4) random ternary-complex mechanism. In each case, a discussion is presented of the way in which the individual rate constants can be separated on the basis of experimental transient-phase investigations.

scholarly journals Steady state kinetics at high enzyme concentration. The myosin MgATPase.

1985 ◽  
Vol 260 (9) ◽  
pp. 5505-5510
Author(s):  
D D Hackney ◽  
P K Clark
Keyword(s):  
Steady State ◽  
Enzyme Concentration ◽  
Steady State Kinetics ◽  
High Enzyme ◽  
High Enzyme Concentration

THEORY OF THE TRANSIENT PHASE IN AN ENZYME SYSTEM INVOLVING TWO ENZYME-SUBSTRATE COMPLEXES: THE CASE OF THE FORMATION OF PRODUCTS FROM THE FIRST COMPLEX

1959 ◽  
Vol 37 (4) ◽  
pp. 737-743 ◽  
Author(s):  
Ludovic Ouellet ◽  
James A. Stewart
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Active Site ◽  
Substrate Concentration ◽  
Enzyme System ◽  
Kinetic Scheme ◽  
Enzyme Concentration ◽  
Theoretical Treatment ◽  
Transient Phase ◽  
Enzyme Substrate

A theoretical treatment is worked out for the kinetic scheme[Formula: see text]in which the concentration of P1 is followed. The steady-state and transient phase equations are obtained subject to the condition that the substrate concentration is greatly in excess of the enzyme concentration. The conditions under which evidence in favor of this mechanism can be obtained from experimental data are discussed. Under certain conditions, the weight of the enzyme corresponding to one active site can be determined. Methods for the evaluation of the different constants are described.

Transient-Phase and Steady-State Kinetics for Enzyme Activation

1973 ◽  
Vol 51 (6) ◽  
pp. 806-814 ◽  
Author(s):  
Nasrat H. Hijazi ◽  
Keith J. Laidler
Keyword(s):  
Steady State ◽  
Kinetic Data ◽  
Enzyme Activation ◽  
Transient Phase ◽  
Time Curve ◽  
Substrate Complex ◽  
Enzyme Substrate ◽  
Substrate Activation ◽  
Steady State Kinetics ◽  
Special Case

A non-steady-state analysis has been worked out for two mechanisms in which an activator Q can become attached to an enzyme–substrate complex EA, the species EAQ breaking down more rapidly than EA. It is shown that if EAQ breaks down into EQ + product there can be no steady state. If, however, EAQ breaks down into E + Q + product, the transient phase is followed by a steady state in which the product versus time curve is linear. A special case of this mechanism is when Q is the substrate (substrate activation). Some published kinetic data on carboxypeptidase are analyzed with reference to the equations derived.

Transient‐phase and steady‐state kinetics of lipase‐catalyzed ester hydrolysis1

1978 ◽  
Vol 13 (2) ◽  
pp. 117-129 ◽  
Author(s):  
M.H. Sadar ◽  
G. Ayranci
Keyword(s):  
Steady State ◽  
Transient Phase ◽  
Steady State Kinetics ◽  
Kinetics Of

scholarly journals The effects of hydrogen ion concentration on the simplest steady-state enzyme systems

1971 ◽  
Vol 123 (3) ◽  
pp. 445-453 ◽  
Author(s):  
P. Ottolenghi
Keyword(s):  
Steady State ◽  
Active Site ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Substrate Complex ◽  
Perturbation Term ◽  
Enzyme Substrate ◽  
Enzyme Systems ◽  
Steady State Kinetics

Laidler (1955) showed that consideration of the effect of pH on enzymic mechanisms that obey steady-state kinetics leads to the inclusion in the equations of a ‘perturbation term’ that can introduce curvature into the Lineweaver–Burk plots. He also stated conditions in which this term vanishes. This term can lead to apparent activation by substrate. Further, several cases are shown in which simplification, but not disappearance, of the perturbation term can lead to linearity of Lineweaver–Burk plots. These cases arise when the ionization of groups at the active site either is unaffected or is completely prevented when the enzyme–substrate complex is formed. It is also shown that V(app.) can vary with pH without a concomitant change in Km(app.) in certain cases that obey steady-state kinetics without implying that Km=Ks. When the perturbation term is significant, Dixon's (1953) rules for the calculation of pK values will not always apply.

THEORY OF THE TRANSIENT PHASE IN KINETICS, WITH SPECIAL REFERENCE TO ENZYME SYSTEMS

1955 ◽  
Vol 33 (10) ◽  
pp. 1614-1624 ◽  
Author(s):  
Keith J. Laidler
Keyword(s):  
Steady State ◽  
Special Reference ◽  
Transient Phase ◽  
Kinetic Behavior ◽  
State Equations ◽  
Enzyme Systems ◽  
Great Excess ◽  
Special Case

The steady-state hypothesis is discussed for enzyme systems, and the conditions under which the steady-state equations will be valid over the main course of the reaction are obtained. It is shown that this is so if the substrate is in great excess, and also under several other circumstances. Equations are derived for the kinetic behavior during the transient phase of the reaction. Two-substrate systems, and the special case of catalase, are considered.

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