Deuterium Isotope Effects on the Presteady State Burstofan Enzymatic Reaction

When a presteady state burst is seen in an enzymatic reaction where a change in absorbance accompanies the isotope-sensitive step, there will be an isotope effect on the initial rate of the burst. The apparent commitment which reduces the size of the intrinsic isotope effect will not be solely the partition ratio of the intermediate undergoing the isotope-sensitive step (as in steady state kinetics), but will also be a function of the ratio of the forward rate constants for the isotope-sensitive step and the one preceding it. A contour map of these relationships is presented.