A method,based on statistical moments,to evaluate the kinetic parameters involved in unstable enzyme systems |
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Authors: | E?Arribas H?Bisswanger A?Sotos-Lomas M?Garcia-Moreno F?Garcia-Canovas J?Donoso-Pardo F?Mu?oz-Izquierdo Email author" target="_blank">R?VaronEmail author |
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Institution: | 1.Applied Physics Department,University of Castilla-La Mancha,Albacete,Spain;2.Eberhard Karls Universit?t,Tubingen,Germany;3.Departamento de Quimica-Fisica, Escuela Politecnica Superior,Universidad de Castilla-La Mancha,Albacete,Spain;4.Departamento Bioquimica y Biologia Molecular A,Universidad de Murcia,Murcia,Spain;5.Departament de Química,Universidad de les Illes Balears,Palma de Mallorca,Spain |
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Abstract: | The evaluation of individual rate constants involved in any reaction mechanism of an enzymatic systems first requires experimental
monitoring of the time course of the concentration or product rate creation or of any enzyme species. The experimental progress
curves obtained must then be fitted to the corresponding theoretical symbolic equation. Nevertheless, in some cases, e.g.
when the equation involves two or more exponential terms, this fit is not easy and sometimes impossible. Simplification of
the equation is usually required by assuming, for example, that the system has reached the steady-state, assuming an initial
steady-state of a segment in the scheme of the reaction mechanism or assuming rapid equilibrium in one or more of the reversible
steps, if there are any. But, obviously, simplified equations produce either fewer individual rate constants or global constants
consisting of algebraic associations of individual rate constants or individual rate constants or global constants that might
considerably differ from the real ones due to the approaches made. In this contribution, we suggest an alternative procedure
for evaluating the rate constants of enzyme reactions corresponding to enzyme systems where one or more of the species involved
is unstable or where one or more of the enzyme species is irreversibly inhibited, or both. The procedure is based on the numerical
determination of statistical moments from experimental time progress curves. The fitting of these experimentally obtained
moments to the corresponding theoretical expressions allows us, in most cases, to evaluate of all of the rate constants involved,
with only a small error. To verify the goodness of the suggested procedure, it was applied to an unstable enzyme system which
had previously been analysed with other methods. Finally, it is indicated how this procedure could also be extrapolated for
application to any stable or unstable enzyme system. |
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Keywords: | Statistical Moment Enzyme Kinetics Unstable |
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