The design equation for a packed-bed immobilized enzyme reactor is expressed in terms of apparent kinetic parameters and the relationship between the exit concentration of substrate consumed and the logarithm of the exit unconverted fraction of substrate is studied. Agreement of calculated values with experimental data indicate that this relationship is not linear but is convex downward. Furthermore, simulation is made to characterize the apparent kinetic parameters. The results show that with increasing flow rates of a reaction mixture, the apparent kinetic parameters decrease rapidly towards their respective intrinsic values. As the entrance substrate concentration increases, on the other hand, these values initially increase, pass through maximums, and finally decrease towards their intrinsic values. These variations are found to occur remarkably with the apparent Michaelis constant.