The proton inventory technique.

The proton inventory technique uses the dependence of enzymic reaction rate on the atom fraction of deuterium present in mixtures of protium oxide and deuterium oxide to deduce for simple cases the number of exchangeable hydrogenic sites that produce isotope effects, and the magnitude of the isotope effect generated at each site. For more complex cases, other information, such as the participation of more than a single step in limiting the rate, may be obtained. The background of the method, the conduct of the experiments and the interpretation of the results are briefly reviewed. The method is then illustrated in its application to various enzyme systems by a series of case histories.