Enzymes are catalysts that drive reaction rates forward. Most, but not all, are made up of amino acid chains called proteins that accelerate the rate of reactions in chemical systems. Their functionality depends on how the proteins are folded as to what they bind and react with. For protein-based catalysts, amino acid polarization lies at the core of catalytic activity.
Enzymes are proteins that speed up the rate of a reaction by providing an alternate route to overcoming the activation energy. The graph below shows the path of a reaction both with and without the presence of an enzyme.
Two 20th century scientists, Leonor Michaelis and Maud Leonora Menten, proposed the model known as Michaelis-Menten Kinetics to account for enzymatic dynamics. The model serves to explain how an enzyme can cause kinetic rate enhancement of a reaction and explains how reaction rates depends on the concentration of enzyme and substrate.
Ping-pong mechanism, also called a double-displacement reaction, is characterized by the change of the enzyme into an intermediate form when the first substrate to product reaction occurs. It is important to note the term intermediate indicating that this form is only temporary. A key characteristic of the ping-pong mechanism is that one product is formed and released before the second substrate binds.
A significant portion of enzymes function such that their properties can be studied using the Michaelis-Menten equation. However, a particular class of enzymes exhibit kinetic properties that cannot be studied using the Michaelis-Menten equation. The rate equation of these unique enzymes is characterized by an “S-shaped” sigmoidal curve, which is different from the majority of enzymes whose rate equation exhibits hyberbolic curves.
