title: Analysis of the kinetic isotope effects on initial rates in transient kinetics.
abstract: A method was described recently for circumventing the difficulties in determining intrinsic kinetic isotope effects from eigenvalues obtained in transient kinetic experiments (Maniscalco, Tally, and Fisher (2004) Arch. Biochem. Biophys. 425, 165-172). The method, based on the isotope effects on initial rates of formation of intermediates, was validated by numerical simulation for only a few linear reaction sequences. A general analytical proof of the validity of the method is given in this work. The mathematical approach, using rate laws and L'Hôpital's rule, allows more complex reaction schemes to be analyzed. Several are analyzed in this article, illustrating the broad applicability and possible complications in this approach for determining intrinsic isotope effects. Some possible applications are noted, with particular attention being paid to nonlinear reaction schemes, the effect of measuring signals rather than concentration, and the ability to distinguish stepwise from concerted reactions.
authors.affiliation: Department of Biological Chemistry, University of Michigan Medical School, 1301 Catherine Road, Ann Arbor, Michigan 48109-0606, USA. brupalf@umich.edu
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Palfey
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Fagan
mesh_terms: D003903:Deuterium; D004798:Enzymes / Q000378:metabolism*; D007554:Isotopes / Q000737:chemistry*; D007700:Kinetics; D008433:Mathematics; D008956:Models, Chemical
chemical_list: D004798:Enzymes; D007554:Isotopes; D003903:Deuterium