Before revision:  In doing so, we extend the established domain of validity for the rQSSA. Previous analysis has suggested that the rQSSA is only valid when initial enzyme concentrations greatly exceed initial substrate concentrations. However, our results indicate that this approximationcan be valid when initial enzyme and substrate concentrations are of equal magnitude . Consequently, this opens  the possibility of utilizing the rQSSA to model enzyme catalyzed reactions and estimate kinetic parameters in enzymatic assays at much lower enzyme to substrate ratios than was previously thought  .
After revision:  In doing so, we extend the established domain of validity for the reverse quasi-steady-state approximation . Consequently, this opens the possibility of utilizing the rQSSA to model enzyme catalyzed reactions and estimate kinetic parameters in enzymatic assays at much lower enzyme to substrate ratios than was previously thought .