Enzyme kinetics at high enzyme concentration

We re-visit previous analyses of the classical Michaelis-Menten substrate-e nzyme reaction and, with the aid of the reverse quasi-steady-state assumpti on, we challenge the approximation d[C]/dt approximate to 0 for the basic e nzyme reaction at high enzyme concentration. For the first time, an approxi mate solution for the concentrations of the reactants uniformly valid in ti me is reported. Numerical simulations are presented to verify this solution . We show that an analytical approximation can be found for the reactants f or each initial condition using the appropriate quasi-steady-state assumpti on. An advantage of the present formalism is that it provides a new procedu re for fitting experimental data to determine reaction constants. Finally, a new necessary criterion is found that ensures the validity of the reverse quasi-steady-state assumption. This is verified numerically. (C) 2000 Soci ety for Mathematical Biology.