Kinetic Behavior at High Enzyme Concentrations

The errors of the Michaelis-Menten equation and three other approximations have been examined in relation to the true rate equation in which the depletion of free substrate by binding to the enzyme is taken into account. The true velocities and errors are computed for various concentrations of the total enzyme and the total substrate. It has been shown that, when the concentrations of the total enzyme and the total substrate both lie within 10-fold of the Michaelis constant, the error of the Michaelis-Menten equation ranges from 0.08 to 900%, whereas that of the Cha-Cha approximation, v = VS/(K + S + E), ranges from 0.7 to 34.8%, and that of the asymptote of the true curve in the reciprocal plot, v = VS/(K + E + KS/(K + E)), ranges from less than 0.1 to 58.5%.