During his years working as a physician Michaelis  a friend (Peter Rona) built a compact lab, in the hospital, and over the course of five years – Michaelis successfully became published over 100 times. During his research in the hospital, he was the first to view the different types of inhibition; specifically using fructose and glucose as inhibitors of maltase activity. Maltase breaks maltose into two units of glucose. Findings from that experiment allowed for the divergence of non-competitive and competitive inhibition. Non-competitive inhibition affects the k value (but not the K) on any given graph; this inhibitor binds to a site that has specificity for the certain molecule. Michaelis determined that when the inhibitor is bound, the enzyme would become inactivated.
Like many other scientists of their time, Leonor Michaelis and Maud Menten worked on a reaction that was used to change the composition of sucrose and make it lyse into two products – fructose and glucose. The enzyme involved in this reaction is called invertase, and it is the enzyme the kinetics of which have been supported by Michaelis and Menten to be revolutionary for the kinetics of other enzymes. While expressing the rate of the reaction studied, they derived an equation that described the rate in a way which suggested that it is mostly dependent on the enzyme concentration, as well as on presence of the substrate, but only to a certain extent.
Adrian Brown and Victor Henri laid the groundwork for the discoveries in enzyme kinetics that Michaelis and Menten are known for. Brown theoretically envisioned the mechanism now accepted for enzyme kinetics, but did not have the quantitative data to make a claim. Victor Henri made significant contributions to enzyme kinetics during his doctoral thesis, however he lacked noting the importance of hydrogen ion concentration and mutarotation of glucose. The goal of Henris thesis was to compare his knowledge of enzyme-catalysed reactions to the recognized laws of physical chemistry. Henri is credited with being the first to write the equation that is now known as the Michaelis-Menten equation. Using glucose and fructose in the catalytic reactions controlled by maltase and invertase, Leonor Michaelis was the first scientist to distinguish the different types of inhibition by using the pH scale which did not exist in Henris time.
Particularly during their work on describing the rate of this reaction they also tested and extrapolated on the idea of another scientist, Victor Henri, that enzyme they were using had some affinity for both products of this reaction – fructose and glucose. Using Henris methods, Michaelis and Menten nearly perfected this concept of initial-rate method for steady-state experiments. They were studying inhibition when they found that non-competitive (mixed) inhibition is characterized by its effect on k (catalyst rate) while competitive is characterized by its effect on velocity (V). In the Michaelis and Menten experiments they heavily focused on pH effects of invertase using hydrogen ions. Invertase is an enzyme found in extracellular yeast and catalyzed reactions by hydrolysis or inverting a sucrose (mixture of sucrose and fructose) to “invert sugar.” The main reason for using invertase was that it could be easily assayed and experiments could be done in quicker manner.  Sucrose rotates in polarimeter as dextroratatory-D whereas invert sugar is levorotatory-L. This made tracking the inversion of sugar relatively simple. They also found that α-D-glucose is released in reactions catalyzed by invertase which is very unstable and spontaneously changes to β-D-glucose. Although, these are both in the dextrorotatory form, this is where they noted that glucose can change spontaneously, also known as mutarotation. Failing to take this into consideration was one of the main reasons Henris experiments fell short. Using invertase to catalyze sucrose inversion, they could see how fast the enzyme was reacting by polarimetry; therefore, non-competitive inhibition was found to occur in the reaction where sucrose was inverted with invertase.