Kinetics enzyme reactions

Measurements of particular properties of a compound or substance (enzyme kinetics, reaction kinetics, FACS, fluorescence-activat cell sorting, assay). 

Bedner, E., Melamed, M.R., and Darzynkiewicz, Z. (1998) Enzyme kinetic reactions and fluorochrome uptake rates measured in individual cells by laser scanning cytometry (LSC). Cytometry, 33, 1-9. 

Substrate Inhibition Substrate inhibition represents another example of cooperativity in enzyme kinetic reactions, but of a different profile than described to this point. With substrate inhibition kinetics, the velocity of a reaction increases (as expected for hyperbolic profiles) to an apex, however, beyond this point the velocity of the reaction decreases with increasing substrate concentrations (Fig. 4.7). 

The binding of iodinated aBgt to AcChR is specific and irreversible [13]. Formation of the receptor-toxin complex, under the conditions described in the methods section, is a very fast process the reaction goes to completion in approximately one minute (Figure 1). Contrary to enzyme kinetics, reaction conditions cannot be chosen such as... 

Most of the transport phenomena are descrihed by linear processes, but, for example, the uptake of inorganic iodine by the thyroid from the blood plasma is primarily a zero-order process, and several enzyme kinetic reactions and bindings are second-order processes. 

Enzyme kinetics Reaction monitoring, proton transfer... 

By protodetritiation of the thiazolium salt (152) and of 2 tritiothiamine (153) Kemp and O Brien (432) measured a kinetic isotope effect, of 2.7 for (152). They evaluated the rate of protonation of the corresponding yiides and found that the enzyme-mediated reaction of thiamine with pyruvate is at least 10 times faster than the maximum rate possible with 152. The scale of this rate ratio establishes the presence within the enzyme of a higher concentration of thiamine ylide than can be realized in water. Thus a major role of the enzyme might be to change the relative thermodynamic stabilities of thiamine and its ylide (432). 

Perez-Bendito, D. Silva, M. Kinetic Methods in Analytical Chemistry. Ellis Horwood Chichester, England, 1988. Additional information on the kinetics of enzyme catalyzed reactions maybe found in the following texts. 

Pisakiewicz, D. Kinetics of Chemical and Enzyme-Catalyzed Reactions. Oxford University Press New York, 1977. 

Enzyme Kinetics. A simple en2yme cataly2ed reaction can be described ... 

For a somewhat more extensive exposure to enzyme reaction kinetics, consult standard biochemistry texts and also Dixon, M. and E. C. Webb, Enzymes, 2d ed.. Academic Press, 1964 Segal, I. H., Enzyme Kinetics, Wiley, 1975 Gacesa, P. and J. Hubble, Enzyme Technology, Open University Press, England, 1987. 

Equation 11-15 is known as the Michaelis-Menten equation. It represents the kinetics of many simple enzyme-catalyzed reactions, which involve a single substrate. The interpretation of as an equilibrium constant is not universally valid, since the assumption that the reversible reaction as a fast equilibrium process often does not apply. 

Lineweaver-Burk plot Method of analyzing kinetic data (growth rates of enzyme catalyzed reactions) in linear form using a double reciprocal plot of rate versus substrate concentration. 

The simplest kinetic scheme that can account for enzyme-catalyzed reactions is Scheme XX, where E represents the enzyme, S is the substrate, P is a product, and ES is an enzyme-substrate complex. 

The relative fluctuations in Monte Carlo simulations are of the order of magnitude where N is the total number of molecules in the simulation. The observed error in kinetic simulations is about 1-2% when lO molecules are used. In the computer calculations described by Schaad, the grids of the technique shown here are replaced by computer memory, so the capacity of the memory is one limit on the maximum number of molecules. Other programs for stochastic simulation make use of different routes of calculation, and the number of molecules is not a limitation. Enzyme kinetics and very complex oscillatory reactions have been modeled. These simulations are valuable for establishing whether a postulated kinetic scheme is reasonable, for examining the appearance of extrema or induction periods, applicability of the steady-state approximation, and so on. Even the manual method is useful for such purposes. 

Kinetics is the branch of science concerned with the rates of chemical reactions. The study of enzyme kinetics addresses the biological roles of enzymatic catalysts and how they accomplish their remarkable feats. In enzyme kinetics, we seek to determine the maximum reaction velocity that the enzyme can attain and its binding affinities for substrates and inhibitors. Coupled with studies on the structure and chemistry of the enzyme, analysis of the enzymatic rate under different reaction conditions yields insights regarding the enzyme s mechanism of catalytic action. Such information is essential to an overall understanding of metabolism. 

Before beginning a quantitative treatment of enzyme kinetics, it will be fruitful to review briefly some basic principles of chemical kinetics. Chemical kinetics is the study of the rates of chemical reactions. Consider a reaction of overall stoichiometry... 

Kinetics of Enzyme-Catalyzed Reactions Involving Two or More Substrates... 

Reactions conforming to this kinetic pattern are characterized by the fact that the product of the enzyme s reaction with A (called P in the following schemes) is released prior to reaction of the enzyme with the second substrate, B. As a result of this process, the enzyme, E, is converted to a modified form, E, which then reacts with B to give the second product, Q, and regenerate the unmodified enzyme form, E ... 

Thus far, we have considered enzyme-catalyzed reactions involving one or two substrates. How are the kinetics described in those cases in which more than two substrates participate in the reaction An example might be the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (Chapter 19) ... 

Gray, C. J., 1971. Enzyme-Catalyzed Reactions. New York Van Nostrand Reinhold. A monograph on qnantitative aspects of enzyme kinetics. 

If the enzyme-catalyzed reaction is to be faster than the uncatalyzed case, the acceptor group on the enzyme must be a better attacking group than Y and a better leaving group than X. Note that most enzymes that carry out covalent catalysis have ping-pong kinetic mechanisms. 

Most enzymes catalyse reactions and follow Michaelis-Menten kinetics. The rate can be described on the basis of the concentration of the substrate and the enzymes. For a single enzyme and single substrate, the rate equation is ... 

The initial reaction rate (v0) obtained from each substrate concentration was fitted to Michaelis-Menten kinetics using enzyme kinetics. Pro (EKP) Software (ChemSW product,... 

Enzyme kinetics. Consider a mechanism for an enzymatic reaction in which the E S complex is a dead end ... 

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