The influence of pH on the rates of enzyme reactions. Part 3.—Analysis of experimental results for various enzyme systems

1955 ◽  
Vol 51 (0) ◽  
pp. 550-561 ◽  
Author(s):  
Keith J. Laidler
Keyword(s):  
Experimental Results ◽  
Enzyme Reactions ◽  
Enzyme Systems ◽  
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.

A COLUMN STUDY OF SOIL CONTAMINATION BY LEAD: INFLUENCE OF pH AND CARBONATE CONTENT. I. EXPERIMENTAL RESULTS

2001 ◽  
Vol 36 (4) ◽  
pp. 437-446
Author(s):  
J. M. Rodríguez-Maroto ◽  
C. Vereda-Alonso ◽  
C. Gómez-Lahoz ◽  
F. García-Herruzo ◽  
R. A. García-Delgado
Keyword(s):  
Soil Contamination ◽  
Experimental Results ◽  
Carbonate Content ◽  
Column Study ◽  
Influence Of Ph

LECITHINASE SYSTEMS IN SUGAR BEET, SPINACH, CABBAGE, AND CARROT

1954 ◽  
Vol 32 (1) ◽  
pp. 571-583 ◽  
Author(s):  
Morris Kates
Keyword(s):  
Sugar Beet ◽  
High Speed ◽  
Thermal Inactivation ◽  
Enzyme Concentration ◽  
Organic Phosphate ◽  
Water Soluble ◽  
Optimum Conditions ◽  
Carrot Root ◽  
Enzyme Systems ◽  
Influence Of Ph

Lecithinase activity of aqueous extracts of sugar beet, spinach, or cabbage leaves, and of carrot root was found to be associated entirely with the plastid fractions, separated by high-speed centrifugation. The supernatant cell sap–cytoplasm fractions were not only inactive but actually inhibitory. The rate of enzymatic liberation of choline from lecithin by all plastid fractions was found to be greatly increased by saturation with diethyl ether. The influence of pH, enzyme concentration, substrate concentration, and temperature on the rate of ether-activated choline liberation was studied and optimum conditions for the reaction were determined. Under optimum conditions, liberation of choline from lecithin by each of the plastid fractions was rapid and was accompanied by a much slower liberation of inorganic and water-soluble organic phosphate; liberation of phosphates was much greater with spinach than with the other species. Thermal inactivation and fluoride inhibition of the enzyme systems were also studied.

scholarly journals A model of digestive tooth corrosion in lizards: experimental tests and taphonomic implications

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Krister T. Smith ◽  
Orr Comay ◽  
Lutz Maul ◽  
Fabio Wegmüller ◽  
Jean-Marie Le Tensorer ◽  
...  
Keyword(s):  
Soft Tissues ◽  
Experimental Tests ◽  
Model System ◽  
Experimental Results ◽  
Deep Time ◽  
Feeding Experiments ◽  
Enzyme Systems ◽  
High Enzyme ◽  
Gastric Fluids ◽  
Owl Pellets

AbstractCorrosion patterns induced by gastric fluids on the skeleton of prey animals may depend on the nature of the corrosive agents (acid, enzymes) as well as on the composition of the hard parts and the soft tissues that surround them. We propose a framework for predicting and interpreting corrosion patterns on lizard teeth, our model system, drawing on the different digestive pathways of avian and non-avian vertebrate predators. We propose that high-acid, low-enzyme systems (embodied by mammalian carnivores) will lead to corrosion of the tooth crowns, whereas low-acid, high-enzyme systems (embodied by owls) will lead to corrosion of the tooth shafts. We test our model experimentally using artificial gastric fluids (with HCl and pepsin) and feeding experiments, and phenomenologically using wild-collected owl pellets with lizard remains. Finding an association between the predictions and the experimental results, we then examine corrosion patterns on nearly 900 fossil lizard jaws. Given an appropriate phylogenetic background, our focus on physiological rather than taxonomic classes of predators allows the extension of the approach into Deep Time.

scholarly journals An approach to better estimation of the intial velocity of enzyme reactions

2019 ◽  
Vol 488 (2) ◽  
pp. 225-228
Author(s):  
N. M. Malygina ◽  
T. A. Petrova ◽  
A. Y. Lianguzov ◽  
A. M. Ivanov
Keyword(s):  
Initial Velocity ◽  
Kinetic Curve ◽  
Enzyme Reaction ◽  
Lag Phase ◽  
Activity Levels ◽  
Salivary Alpha Amylase ◽  
Reaction Velocity ◽  
Enzyme Reactions ◽  
Enzyme Systems ◽  
Assay Time

A new algorithm for computation of initial velocity of enzyme reaction at the time zero is proposed. This algorithm makes it possible to reduce systematic error of measurements to the minimum, to estimate reaction velocity in testing samples regardless of the enzyme activity levels and to minimize assay time. The study is illustrated by an example of salivary alpha-amylase and standard reagent kit. The algorithm should not be applied if conjugated enzyme systems are used because there is a long initial lag-phase in the kinetic curve.

scholarly journals THE KINETICS OF ENZYME REACTIONS: SCHÜTZ'S LAW

1930 ◽  
Vol 13 (3) ◽  
pp. 323-334 ◽  
Author(s):  
E. A. Moelwyn-Hughes ◽  
J. Pace ◽  
W. C. M. Lewis
Keyword(s):  
Experimental Results ◽  
Mass Action ◽  
Law Of Mass Action ◽  
Enzyme Reactions ◽  
Adsorption Theory ◽  
The Law ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Tryptic Hydrolysis ◽  
Made In

1. A review of the applicability of Schütz's Law to enzymic reactions is given. 2. The theoretical deductions of the Law, (a) on the basis of the law of mass action, (b) on the basis of the adsorption theory, are given and the significance of the assumptions made in these deductions pointed out. 3. It is shown that the true critical increment for an enzymic reaction is equal to twice the critical increment calculated from the Schütz constant ks, if the heat of decomposition of the enzyme-products complex be neglected. 4. Experiments are described on the tryptic hydrolysis of casein at 30°C. and 404C. The foregoing considerations are applied to the experimental results obtained.

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.

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