Trypsin Enzyme Kinetics Experiment Analysis

An experiment is designed to investigate the effect of trypsin concentration on its enzymatic activity, measured by the reduction in absorbance of a milk suspension over time. The experimental setup involves preparing five different trypsin concentrations (0.2%, 0.4%, 0.6%, 0.8%) by diluting a stock solution to 10cm³ each, setting a colorimeter to zero absorbance with a control cuvette, mixing 2cm³ of milk suspension with 2cm³ of trypsin solution, and immediately measuring absorbance initially and every 15 seconds for five minutes or until change is minimal. Control variables include temperature, volume of enzyme, volume of substrate, concentration of substrate, and pH. If, as expected, a graph plotting the initial rate of reaction against trypsin concentration shows an initial increase followed by a plateau, what fundamental aspect of enzyme kinetics does this plateau primarily indicate, while assuming all specified control variables are perfectly maintained but considering the inherent limitations of enzyme-substrate interactions?