Isotope Transfer at Equilibrium

Abstract

The study of isotope transfer between a given substrate and product pair in an enzyme-catalysed reaction can be used, if the concentrations of all the products are initially zero, as a means of obtaining initial velocity data for the reaction. A different situation arises if the products are present, for now the measurement of isotope exchange provides information about the rates of individual steps, or sequences of steps, in a reaction which is influenced by the concentrations of all the reactants; indeed, this information is usually obtained from experiments where the reactants have reached their equi­librium concentrations and where no net rate of chemical reaction can be measured.